STUDIES ON INTERACTION OF ROOT-KNOT NEMATODES AND ROOT-INFECTING FUNGI

ON AIR POLLUTION STRESSED LEGUMINOUS CROPS

DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS

FOR THE AWARD OF THE DEGREE OF

jWas^ter of ^jjilosfopljp IN

AGRICULTURE

SYED ABBAS KOSSEINI-NBGAD

AGRICULTURE CENTRE ALIGARH MUSLIM UNIVERSITY

ALIGARH (INDIA)

1991

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Dr. M. Uajid Khan H . S c , Ph.D., F.L.S., F.P.S.I.

Reader

AGRICULTURE CENTRE DEPARTMENT OF BOTANY ALI6ARH HUSLIM UNIVERSITY ALIGARH-202002 (U.P.) INDIA

Certificate

This i s to certify that Mr. Syed Abbas Hosselni Negad

has worked in this centre as a Research Scholar under my

guidance. His dissertation on Studies on interaction of root-knot

nematodes and root-infecting fungi on air pollution stressed

leguminous crops is original and upto-date. He i s allowed to

submit this dissertation for consideration of the award of the

degree of Master of Philosophy in Agriculture (Plant Pathology).

(M. WAJID KHAN) RESEARCH SUPERVISOR

ACKNOWLEDGEMENTS

Submission of the present dissertation provides me the

best opportunity to express profound sense of gratitude and

sincere thanks to my supervisor Dr.M. Wajid Khan, Reader,

Agriculture Centre, Department of Botany, Aligarh Muslim

University, Aligarh for suggesting the problem,

encouragement, inexhaustible source of inspiration, his able

guidance and supervision and valuable suggestion during the

preparation of this manuscript. It has been indeed a proud

privilege to learn from him as a research supervisor.

The cooperative attitude of Prof. Syed Israr Husain,

the present and Prof. Khalid Mahmood, the Ex-Coordinator of

the Agriculture Centre, A.M.U., Aligarh in providing

necessary facilities is greatly appreciated.

Thanks are also due to Prof. Abrar M.Khan, Professor

Emeritus, Department of Botany, A.M.U., Aligarh for his

encouragement and valuable suggestions.

I would like to place my thanks to Dr. Saad Ashraf, Dr.

Abrar Ahmad Khan, Dr. Mujeebur Rahman Khan, Dr. Nisar Ahmad

Ansari and Mr. Kamal Singh for their help and cooperation.

I offer my heartiest respect to my most affectionate

parents who have always been a source of inspiration,

encouragement, patience and support.

yLz-A^ SYED ABBAS HOSSEINI-NEGAD

TABLE OF CONTENTS

PAGE

INTRODUCTION 1

LITERATURE REVIEW 17

Air Pollution and Plants 19

Effects of Air-borne Sulphur Pollutions 20 on Plants

Susceptibility and Resistance of 34 Plants to SOg

Physiological and Biochemical effects 35 of SOg on Plants

Nematode Parasites of pulses 40

Pulses and Soil-borne Fungal Pathogens 42

Interaction of Sulphur Dioxide and Plant 49 Parasites

Fungal Plant Pathogens and Sulphur Dioxide 49

Plant Parasitic Nematodes 55

Plant Pathogenic and Nodule-forming Bacteria 60

Interaction of Sulphur Dioxide with other 62 Air pollutants

Interaction of Nematodes with other Soil-borne 64 Plant Pathogens

Nematode and Fungal Plant Pathogens 66

(a) Interaction with Wilt causing Fungi 69

(b) Interaction with Root-rot Fungi 81

Interaction of Nematode and Fungal Plant 90 Pathogens under Pollution Stress

MATERIAL AND METHODS 93

1. Root-knot Nematode Population 93

(a) Collection of Field Populations 93

(b) Identification of Species

(i) Perineal Pattern Method

(ii) North Carolina Host Differential test

(c) Maintenance of Inoculum

(d) Inoculation

Inocula of F. oxysporum f.sp. ciceris and R. bataticola

(a

(b

Po

(a

(b

(c

(d

(e

(f

(g

(h

(i

Maintenance and Pure Culturing

Preparation of Inoculum

lutant (Sulphur Dioxide)

Exposure Chamber

Generation of SOg Gas

Exposure and Doses

Air Pollution Symptoms

Sampling

Analysis of Sulphur Dioxide

Standardisation of Sodium Thiosulphate

Standardisation of Metabisulphite Solution

Working Standard Metabisulphite solution in Absorbing Media

(j) Calibration of Standard Curve

(k) Estimation

4. Pathogenicity Tests

Pathogenicity of M. incognita

Sensitivity to SOg

5. Interaction Studies

(a) Interaction of M. incognita with wilt and root-rot fungi

93

93

94

95

95

96

96

96

S<

CL

99

100

100

100

101

103

104

104

105

106

106

108

109

110

110

(b) Interaction of SOg with wilt and root-rot 111 fungi

(c) Interaction of SOg with M. incognita 112

(d) Interaction between SOg, wilt and root-rot 112 fungi and M. incognita

6. Laboratory Experiments 113

(a) Effect of SOg on Hatching and Mortality of 113 M. incognita

(b) Effect of Acidified Soil on Hatching and 114 Mortality of M. incognita

7. Measurement of Soil pH. 116

8. Raising of Seedlings 115

9. Rhizobium inoculation 115

10. Parameters 116

11. Root Nodule Bacteria 116

LITERATURE CITED 117

LIST OF TABLES

TABLE No. PAGE

1. Maximal Permissible Concentrations of Harmful 21

Substances in the Air over Polluted Areas

2. Response to Sulphur Dioxide-Acute effects 25

3. Response to Sulphur Dioxide-Chronic effects 29

4. Response to Sulphur Dioxide-Subtle effects 31 5. Differentiation between three types of Plant 32

effects caused by SOp

6. Interaction of Sulphur Dioxide and Plant 50 Pathogenic Fungi

7. Effect of Air Pollution on Plant Parasitic 56 Nematodes

8. Interaction of Sulphur Dioxide (SOg) and Plant 61 Pathogenic Bacteria and Viruses

9. Effect of Sulphur Dioxide Mixture with other 65 Pollutants on soybean

10. Interaction of Root-knot Nematodes with Wilt 83 causing Fusaria and Root-rot Fungi

11. North Carolina Differential Host Test Reaction 97 Chart

INTRODUCTION

Pulses are one of the most important sources of protein

in human dietary system. Their importance becomes more

appreciable for vegetarian populations particularly in India,

otherwise they would suffer from protein deficiency. Pulses

are used as a food in a variety of forms. The most common is

the soup, the split pulse grain being boiled in spiced water,

grains (seeds) may be ground and boiled, roasted or fried.

Pulses are also grown as fodder crops. Their yrainr ^rc

used also as concentrates to enrich the diet of the animals.

Some pulse crops grown also as green-manure crops and are

excellent for this purpose. They fix atmospheric nitrogen

symbiotically in association with root nodules bacteria and

show no dependence on nitrogen fertilizers. Their ability to

thrive under a wide range of soil and climatic conditions,

specially with their deep root system and ability to with­

stand dry conditions more successfully than most other

commonly grown crops are excellent. Therefore, some of the

pulse crops are suitable for dry farming and can figure

prominently in soil conservation programmes.

One of the most important pulse crop grown in India is

gram {Cicer arietinum L.). It is a multipurpose pulse crop

grown throughout the country for various uses. Its leaves are

as a vegetable, spiced and cooked. In general, it is a rich

source of protein, fat, carbohydrate and vitamins.

Soybean, Glycine max (L.) Merr., is another Important

legume grown mainly as a food crop in various parts of the

world. In recent years, soybean has attained great importance

in the U.S.A which shows the highest acreage under this crop.

The cultivation of this crop in India is also getting

significance. Because of its high nutritional values and good

quality of oil, soybean seeds have been put to a wide rang*

of uses through-out the world. Seeds of soybean are consumed

green, dry or sprouted, besides making various products such

as soymilk, soysauce, cheese called 'Tofu' and curd. The

soybean milk can be used for feeding infants. In the U.S.A.

although it is grown essentially as an oil seed crop and more

than 90 percent of the produce is annually crushed for oil,

it has vast diversification of industrial ulitization. The

commercially important by-products of oil industry include

lecithin, soap stock and oil meal for livestock and poultry;

and the edible ones comprise margarines, shortening and salad

oils. The non-edible outlets are paints, varnishes, inks, oil

cloth, enamel and linoleum.

Recently attention of the Indian Council of

Agricultural Research was drawn to the problem of pulses in

India and an integrated All India Coordinated Programme for

the improvement of pulse crops has been undertaken. The work

is being done in collaboration with U.S. Department of

Agriculture at different centres in India.

The nutritive quality of the pulse grain is an

important aspect of research work which is considered by the

plant breeders from the beginning of the programme. The plant

breeders has also considering the disease and pests problems

which causes severe damage to the crops.

Like many other crops pulses are attacked by a numtcr

of plant pathogen. Fungi, bacteria, viruses and nematodes are

common pathogens that cause an array of diseases of economic

consequences. The most important fungi attacking the aerial

parts of the crops are Ascohyta rabiei causing blight,

Uromyces phaseoTi (rust), Alternaria spp. (leaf blotch),

Botrytis spp. (chocolate spot), Erysiphe polygoni (powedy

mildew), Stemphylium spp. (Chlorosis of leaves), Cercospora

spp., Pleospora herbarum, Colletotrichum limdemuthianum f.

sp. phaseoli (anthracnose). Colletotrichum destructivum,

Leviuellula taurica Lev. (powdery mildew), Oidium spp. and

Helminthosporium spp. The fungal pathogen of roots of pulses

are Rhizoctonia bataticola, R. solani, Fusarium oxysporum, F.

lateritium, F. culmorum, F. avenaceum, Phythium spp.,

Phialophora spp. Peyronelleae spp. and Sclerotium rolfsii.

Among the bacterial diseases of pulses, bacterial blight

caused by Pseudomonas glycinea Coerper, bacterial pustule

caused by Xanthomonas phaseoli and w i l d f i r e caused by

Pseudomonas tabaci (Wolf and Foster) F.L. Steven, are the

most important ones. Pulses a lso s u f f e r from v i r a l diseases

t o o . Some examples are Bean Common Mosaic V i rus (8MV), Common

Aphid t r a n s f e r r e d Mosaic v i r u s (CAMY), Bean Yellow Mosaic

V i rus (BYMV), Bean Mosaic V i rus (BMV), and Pea Mosaic V i rus

(PMV).

Among the f unga l d isease o f c h i c k - p e a and soybean ,

Fusarium oxysporum f . sp. ciceris (Padwick) Chattopedhyay ar"-'

Sen Gupta and Rhizoctonia bataticola ( T a u b . ) Bi. 1 .

(.=Sc1erotium bataticola Taub.) causing w i l t and r o o t - r o t of

t h e i r r e s p e c t i v e hosts have been f o u n d t o be t h e most

s e r i o u s i n I n d i a and a r e o f t e n r e s p o n s i b l e f o r " s o i l

s ickness" problem when the s o i l becomes heav i l y contaminated

w i t h them due t o cont inuous crop c u l t i v a t i o n .

A v a r i e t y o f p l a n t p a r a s i t i c nematodes have been

found i n a s s o c i a t i o n w i t h p u l s e s . Spec ies o f Heterodera,

MeToidogyne, RotylenchuTus, Tylenchorhynchus, Aphelenchoides,

Xiphinema, He!icotylenchuTus, Hemicriconemoides. Paraphelen-

chus, Paratrichodorus, Hoplolamis, HirschmanieTIa, Macro-

posthoni a, Pratyl enchus, Cri conemoi des, Di tylenchus,

Diptherophora, Tylenchus, Caloosia, Telotylenchus, Aglenchus,

and Orisitylus are recorded on pulses (Singh and G i l l , 1990).

Among a l l m e n t i o n e d above , r o o t - k n o t n e m a t o d e s ,

MeToidogyne s p p . w i t h a w o r l d - w i d e d i s t r i b u t i o n and

d i v e r s i f i e d host range are a ser ious pest of pu lses. They

a t t a c k a lmost a l l t he pu lses and t h e i r p a t h o g e n i c i t y have

been es tab l i shed . Meloidogyne incognita causes a s i g n i f i c a n t

r e d u c t i o n i n g r o w t h p a r a m e t e r s o f mo thbean , Vigna

aconitifolius Jacq. (Mishra and Gaur, 1981a), f rench bean,

PhaseoTus vulgaris (Singh e t a1. , 1981), black gram, Vigna

mungo (Mishra and Guar, 1981 b ) , c l u s t e r bean, i.y^.monfis

tetragonaloba (Verma et a / . , 1 9 8 1 ) , pea , Pisum sativum

(Upadhyay and Kusum Dwivedi 1987), cowpea, Vigna unguiculata

( V a r s h n e y et al. , 1 9 8 1 ) , w inged bean , Psophocarpus

tetragonabola (Nayak e t a / . , 1987), soybean, Glycine max

( N a l i n i e t a / . , 1985; K i n l o c h , 1980 ) , c h i c k - p e a , Cicer

arietinum (Mani and S e t h i , 1987; Kumar e t al., 1988 ) . M.

Javanica a lso a t t acks pulses e . g . chick-pea (Goel and Gupta

1984, 1986), pigeonpea, Cajanus cajan (Ngauma and Saka, 1986;

Abdul Salam and Khan 1986), b lackeye bean, Vigna sinensis

(Thomason, 1958). M. arenaria a lso i s a l i m i t i n g f a c t o r i n

p roduct ion of soybean (K in loch e t al., 1987; Rodriguez-Kabana

and W i l l i a m s , 1981) . Soybean c y s t nematode. Heterodera

glycines has been repor ted t o be one of the most widespread

and damaging nematodes of soybean (K in loch , 1980; Wrather and

Anand, 1988).

Females o f r o o t - k n o t nematodes a re s e d e n t a r y

endoparasi tes. Ce l l s around the head and neck of the female

nematodes becomes mul t inuc leated and c e l l wal l i r r e g u l a r l y

th ickened. Usual ly 6-12 of such c e l l s are found around the

neck of each female which f u n c t i o n as t r a n s f e r c e l l s (Jones

and No r thco te , 1972b) and female nematodes o b t a i n t h e i r

n u t r i t i o n from them. Vascu lar t i s s u e s o f t he p l a n t a re

a l t e r e d e x t e n s i v e l y due to i n v a s i o n o f r o o t s by r o o t - k n o t

nematodes which impair the absorpt ion and t rans 1 j c a t t o r o*

w a t e r and n u t r i e n t s t o v e g e t a t i v e p a r t s o f t h e p l a n t .

Suppression o f p l a n t growth and appearance o f d e f i c i e n c y

symptoms on leaves are due t o biochemical changes induced by

the nematodes in the host and a l t e r e d physiology due t o the

anatomical t rans fo rmat ions .

The second s t a g e j u v e n i l e ( J 2 ) o f t h e nematode

penetrates i n t o the root and moves through the cor tex i n t e r -

and i n t r a c e l l u l a r l y t i l l i t reaches c lose t o the p e r i c y c l e .

The f e m a l e become s a c c a t e and s e d e n t a r y and m a i n l y

r espons ib l e f o r pathogenic damages caused t o t h e h o s t

p l a n t s . Root-knot nematode i n t e r a c t s w i t h s o i l - b o r n e p l a n t

pathogens. Synerg is t i c i n t e r a c t i o n s of roo t - kno t nematodes

and severa l s o i l - b o r n e f u n g i a re w e l l documented P o w e l l ,

1971, 1979; Khan, 1984; T a y l o r , ( 1979 , 1991) . R o o t - k n o t

nematodes suppress the format ion of r oo t -nodu la t i on i n pulses

(Dhanger and Gupta, 1983: Rau t i , 1980; Mani & Sethi 1984,

1987), as a r e s u l t o f which the t o t a l b e n e f i t f r o m t h e

n i t rogen f i x i n g bac te r i a i s reduced.

Atmospheric p o l l u t i o n i s a major problem of the modern

w o r l d . The f a s t i n c r e a s i n g human p o p u l a t i o n and q u e s t f o r

improvement i n l i v i n g s tandard have r e s u l t e d i n t o r a p i d

i n d u s t r i a l i s a t i o n , u rban isa t ion , excessive use of f e r t i l i z e r s

and pes t i c i des on major a g r i c u l t u r a l crops and p roduc t ion of

n u c l e a r e n e r g y . C o n s e q u e n t l y , e v e r y component o f t h e

biosphere i . e . the a i r and the s o i l , i s becnmin; t rcme r r'r i^ely

p o l l u t e d by day and n i g h t . A c c o r d i n g t o t h e ^n- 'mates o f

Steve Van Matre (1984), i n the present wor ld on ly 20% of the

a i r i s breathable and only 10X of the land i s capable o f

being e x p l o i t e d f o r producing food. Astan in and Blagosklonov

(1983) r epo r t ed t h a t hundreds o f m i l l i o n s t o n s o f h a r m f u l

gases and dus ts are em i t t ed i n t o t h e e a r t h ' s a tmosphere

every year.

The release of harmful chemicals and t o x i c ma te r i a l s

from i n d u s t r i e s i n t o the environment ( a i r , water , s o i l ) cause

damaging e f f e c t s on both fauna and f l o r a . These t o x i c wastes

i n excess, exceeding the normal s e l f - r e g u l a t i n g capac i t y of

atmosphere, lead t o p o l l u t i o n . Weber (1982) d e f i n e d a i r

p o l l u t i o n as ' t h e presence o f subs tances i n t h e amb ien t

atmosphere, r e s u l t i n g f rom the a c t i v i t y o f man or f r o m

n a t u r a l p rocesses , causing adverse e f f e c t s t o man and t he

environment". In 1966, the committee on pollution, National

Academy of Sciences, U.S.A. defined the pollution as an

undesirable change in the physical, chemical or biological

characteristics of our air, land and water, that may or will

harmfully affect human life or that of desirable species, our

industrial processes, living conditions and cultural assets,

or that may or will waste our raw material resources

(Anonymous, 1966). In other word, any undesirable change in

the physico-chemical and biological properties o^ air, wate-

and soil, which may cause harm to man, other organisms, -.-r t

cultural and natural elements of man's environment, is

pollution.

Environmental pollution includes many kinds of

pollutions such as soil pollution, water pollution, noise

pollution and air pollution. However, the last one probably

has attracted the attention of the world most. Wood (1968)

classified the toxic substances responsible for air pollution

"air pollutants" basically in two categories based on their

origin. Primary air pollutants, those originating at the

source in the form of toxic to living organisms which may be

in gaseous or particulate forms. Gaseous air pollutants are

sulphur dioxide (SOg), oxides of nitrogen (NO^^), hydrogen

fluoride (HF), ammonia (NHg), ethylene (Cg Hg) etc. and

particulate air pollutants are coal dust, cement dust, fly

ash, suspended particulate matter (SPM) etc. The second

category of pollutants are secondary air pollutants which

originates from the reaction between primary air pollutant

that originate from the source e.g. photochemical pollutants

like peroxyacetyl nitrate (PAN) and ozone (O3). SO2 and NOj.

in high humid conditions are converted into acid (Hg SO^ and

HNO3) which fall on the ground in form of 'acid rain' during

the atmospheric precipitation (Oden, 1968).

Sulphur dioxide is one of the most damaging air

pollutant for plants. Sulphur dioxide make entry throLph

stomata to reach the mesophyll of the leaves and t'lut hfeviriu

come in contact with water, change in H2 SO3 or HC03~ if the

— ? — ? medium is acidic, or SO3 - 80^ when alkaline, which

damages to adjoining tissues making for chlorosis and drying

of leaf tips, etc.

P l a n t s a r e a f f e c t e d by t h e p resence o f gaseous

p o l l u t a n t s i n t he a i r . The pe r fo rmance o f t he p l a n t s i s

i n f l u e n c e d d i r e c t l y o r i n d i r e c t l y by i n h i b i t i o n o r

a c c e l e r a t i o n of the p lan t metabol ism, which may in f luence

t h e i r p r o d u c t i v i t y . Many s i g n i f i c a n t and somet imes

devas ta t ing e f f e c t s of a i r p o l l u t i o n of vegetat ion have come

t o l i g h t d u r i n g the c u r r e n t c e n t u r y . Some e a r l i e r r e p o r t s

have revea led the d e v a s t a t i n g e f f e c t o f SOg, f l u o r i d e ,

hydrogen c h l o r i d e and other p o l l u t a n t on p lant popu la t i on .

Recently Temmerman (1982) descr ibed the e f f e c t of ammonia on

v e g e t a t i o n , f o l l o w i n g an a c c i d e n t a l r e l e a s e o f t h e gas.

1 O

A s t a n i n and Blagosklonov (1983) conc luded t h a t v a r i o u s

a f f l i c a t i o n s of p l a n t leaves appear under the i n f l uence of

a i r p o l l u t a n t s and the p lan t growth i s s tun ted. Leaves are

probably the most s e n s i t i v e p lan t par ts to a i r p o l l u t i o n s .

They f i r s t d e v e l o p c e r t a i n p r o t e c t i v e a d a p t a t i o n and

u l t i m a t e l y f a l l prey to the harsh a tmosphere. Stomata and

t r i chomes u s u a l l y undergo changes p e r t a i n i n g t o s i z e and

f r e q u e n c y . P h o t o s y n t h e s i s , a p r o c e s s r e s p o n s i b l e f o r

sustenance of the whole p lan t body i s murh vu lnerab le '• p-'r

p o l l u t i o n damage. The i n f l u e n c e of t o x i c 9ast. . on

a g r i c u l t u r a l crops i s l i t t l e s t u d i e d . However, i n some

i n d u s t r i a l i z e d coun t r ies a i r p o l l u t i o n i s known t o reduce the

y i e l d of many crops near i n d u s t r i a l areas. Plants a f f e c t e d by

su lphu r d i o x i d e are poor i n p r o t e i n ; the sugar bea t s and

potatoes show reduc t ion in sugar and s tarch r e s p e c t i v e l y . The

g r e a t e s t harm t o U.S. a g r i c u l t u r e i s i n f l i c t e d by p h o t -

o x i d a n t s . For example, i n the Los Ange les , V a l l e y f a r m e r s

were fo rced to cease growing c e r t a i n vegetables (sp inach ,

l e t t u c e ) most s u s c e p t i b l e t o p h o t o - o x i d a n t s (ozone and

peroxyacety le n i t r a t e ) , and the c i t r u s f r u i t y i e l d decreased

by 50% (Astan in and Blagosklonov, 1983).

Deposi t ion of p a r t i c u l a t e a i r p o l l u t a n t on lea f sur face

b locks the stomatal c a v i t i e s which hampers t r a n s p i r a t i o n and

checks the t ransmiss ion of so la r r ad ia t i on (Dar ley , 1966).

1 1

Their deposition reduces plant vigour, growth and

productivity.

In agricultural field plots, plants are exposed to a

variety of biotic and abiotic pathogens, especially roots,

which are constantly exposed to many soil microorganisms.

According to Richards (1976), one square meter of highly

fertile field soil may contain as many as 3 x 10 bacterial

cells (300g), 5x10® protozoa (39g), 1x10^ nematodes (12g),

and 400g of fungi. However, this can not generalized for a"ii

soils, and many microbes present are saprophytic or have weak

pathogenic potential to plants. Many investigators have

concluded that the majority of root diseases have a complex

etiology (Grogan 1981; Wallace 1978). Fawcett (1931) stated

that nature does not work with pure cultures and that most

plant diseases, particularly root diseases, are influenced by

associated micro-organisms. Root infections by one pathogen

may modify the host response to subsequent infections by

pathogen or saprophytes.

Nematodes and soil-borne micro-organisms thrives best

under moist soil condition. A number of excellent reviews on

the interactions of plant-parasitic nematodes with other

plant pathogens have been written by Bergeson, (1972)

Pitcher (1963, 1965, 1978), Powell (1963a, 1963b, 1971a,

1971b, 1979), Taylor, (1979, 1991) and Wallace, (1978). The

1 2

rev iews analyse many s p e c i f i c i n t e r a c t i o n s and i n most

i n t e r a c t i o n s i nvo l v i ng fungi and nematodes, nematode was not

essen t ia l f o r the establ ishment and development of the fungal

p a t h o g e n . The nematode u s u a l l y a s s i s t e d t h e f u n g u s by

a l t e r i n g the inc idence and speed o f deve lopment o f t h e

pathogen and thus increas ing the disease s e v e r i t y . Thus, the

i n t e r a c t i o n between the nematode and the fungal pathogen i s

o f ten i n d i r e c t and occurs owing t o induced m o d i f i c a t i o n s i n

the host p l a n t . I n case o f e c t o p a r a s i t i c nematodes, h o s t -

p l a n t m o d i f i c a t i o n may be m i n i m a l , whereas •« n s e d e n t a r y

endoparas i t i c nematodes such as r o o t - k n o t nematodes, these

m o d i f i c a t i o n s are ex tens i ve and c o m p l e x . Bowman et al.,

(1966) r e p o r t e d both l o c a l i z e d and s y s t e m i c h o s t - t i s s u e

m o d i f i c a t i o n s t h r o u g h t h e p r o d u c t i o n o f t r a n s l o c a b l e

m e t a b o l i t e s by nematodes. However, t h e nematodes and t h e

fungal pathogens may occas iona l l y ac t d i r e c t l y on each o t h e r .

Another type of mu l t i p le -pa thogen i n t e r a c t i o n i s the

i n t e r a c t i o n between b i o t i c and a b i o t i c ( a i r p o l l u t a n t s )

pathogens. A i r p o l l u t a n t s are emi t ted t o the atmosphere from

the po in t sources cont inuously and spread i n a l l d i r e c t i o n s

depending upon d i r e c t i o n and v e l o c i t y of the wind, a f f e c t i n g

p lan ts growing in the v i c i n i t y . Therefore on a i r p o l l u t i o n s

s t ressed p l a n t s , associated microorganisms i nc l ud i ng p l an t

pa ras i tes are l i k e l y to be a f f e c t e d . At p resen t , very l i t t l e

i s known of the e f f e c t of p o l l u t a n t s on p a r a s i t i c diseases

-I ?

of plants and host parasite relationships. Some studies

however, have been undertaken to determine this aspect of air

pollution impact. Theoretically, parasitism may be affected

by air pollutants in different ways. Parasitism may be

increased or decreased through a direct effect of pollutant

on the parasite, or the effects may be indirect through

pollutant - induced changes in the host plant. Sulphur

dioxide may act directly upon the fungi or indirectly' throuf*-

some effect upon living or dead plant tissue, soil cr waLf

Studies undertaken show that fungi differ in their reaction

to SO2; rust diseases and wood-destroying fungi are sensitive

to SOg. Wheat stem rust, Puccini a graminis was less in

industrialized area than unindustrialized areas (Johanson,

1954). Scheffer and Hedgcock (1955) found decreased

parasitism by species of Cronarti urn. Coleospori um,

Melampsora, Peridermium, Pucciniastrum, and Puccinia where

trees were injured by SOg. Sulphur dioxide affects fungal

growth too. Hyphae of different species vary in sensitivity

to SOp exposures (MacCallan et al. , 1940).

Pollutants also affect the nematode parasitism.

Reproduction of Heterodera glycines and Paratrichodorus minor

was decreased by Og alone or in mixture of SOg, but that of

Belonolaimus longicaudatus and Pratylenchus penetrans will

not altered (Weber et al. , 1979). Reproduction of P.

penetrans on tomato was slightly suppressed by O3 at 0.20 ppm

1 -4-

but not by SOg a t 0.80 ppm (Brewer 1979). Kozlowska (1981)

o b s e r v e d t h a t i n d u s t r i a l d u s t has h a r m f u l e f f e c t on

Panagrolaimus rigidus. B isessar e t al., (1984) found t h a t

r oo t - kno t nematode (Af. hapTa) i n fec ted tobacco p lan ts were

more s e n s i t i v e t o ambient ozone. However, non- in ju r ious doses

o f SO2 f a i l e d t o a f f e c t a d v e r s e l y t h e p l a n t - p a r a s i t i c

n e m a t o d e s . R e p r o d u c t i o n o f Praty lenchus penetrans was

inc reased when p l a n t s were exposed t o SO2 b e f o r e nematode

i n o c u l a t i o n . Th i s dose o f SO2 was no t enough t o i n j u r e

leaves or s i g n i f i c a n t l y t o a f f e c t p l an t growth. Singh (19£;s)

observed t h a t i nc idence o f i n f e c t i o n o f c h i c k - p e a by M.

incognita and M. Javanica were less around the p o l l u t i o n

sou rce . The i nc i dence o f d i s e a s e was decreased w i t h t h e

inc reas ing d is tance from the p o l l u t i o n source. He observed

t h a t a i r p o l l u t i o n i n general i n h i b i t e d the roo t -kno t disease

on pulse crops in ambient c o n d i t i o n . The extent of i n h i b i t i o n

was c o r r e l a t e d w i t h the ambient l e v e l s o f p o l l u t a n t s . He

noted t h a t j u v e n i l e hatching of both species were adversely

a f f e c t e d by SO2, O3 and t h e i r m i x t u re . Higher concent ra t ions

o f each p o l l u t a n t s i n d i v i d u a l l y o r i n m i x t u r e were more

i n h i b i t o r y t o j u v e n i l e hatch ing and M. incognita was more

s e n s i t i v e than M. javanica t o p o l l u t a n t s . However, much i s

n o t known a b o u t such i n t e r a c t i o n and needs more

i n v e s t i g a t i o n . Although some s tud ies have been undertaken to

determine the e f f e c t of a i r p o l l u t i o n on nematodes or fungal

d isease, the impact of a i r p o l l u t i o n s t ress on development of

1 a

f u n g u s - n e m a t o d e comp lexes on c r o p p l a n t s i s y e t t o be

i n v e s t i g a t e d .

The main o b j e c t i v e of the proposed work i s t o ace r t a i n

the impact o f a i r p o l l u t i o n caused by SOg on r o o t - k n o t -

fusar ium w i l t i n t e r a c t i o n on ch ick-pea and r o o t - k n o t - r o o t r o t

i n t e r a c t i o n on soybean.

E x p e r i m e n t s w i l l be c a r r i e d o u t under a r t i f i c i a l

t r e a t m e n t c o n d i t i o n s i . e . u s i n g exposure cha.oer ^ M . ' V,

t rea tments . The f o l l o w i n g aspects are proposed t o be s tud ied

t o achieve main o b j e c t i v e of the s tudy.

1 . P a t h o g e n i c i t y t e s t of r o o t - k n o t nematode, Meloidogyne

incognita on chick-pea and soybean c u l t i v a r s .

2. Pathogen ic i ty t e s t of w i l t fungus (Fusarium oxysporum f .

sp. ciceris) on chick-pea c u l t i v a r s and r o o t - r o t fungus,

Rhizoctonia bataticola on soybean c u l t i v a r s .

3 . E f f e c t o f s u l p h u r d i o x i d e on c h i c k - p e a and soybean

c u l t i v a r s .

4 . E f f e c t o f M. incognita i n f e c t i o n t o w i l t o f c h i c k - p e a

caused by F. oxysporum f sp. cicers and r o o t - r o t of

soybean caused by R. bataticola.

1 6

5. Interaction of M. incognita and F. oxysporum f. sp.

ciceris on chick-pea and M. incognita and /?. bataticola

on soybean.

6. Interaction of root-knot nematode, M. incognita and SOp

on chick-pea and soybean.

7. Interaction of SOg with F. oxysporum of sp. ciceris on

chick-pea and /?. bataticola on soybean.

8. Impact of SOg on interaction of M. incognit wth P.

oxysporum f. sp. ciceris and /?. £jatat7co7a on their

respective hosts i.e. chick-pea and soybean.

These aspects can be suitably modified depending upon

the progress of the work and results obtained.

LITERATURE REVIEW

1 7-

Total land under the cultivation of pulse crops in

India is about 24 million hectare, with approximate

production of 12 million tons annually. According to Vavilov

(1951) India and Middle East form the primary centre of

origin of most of the important legumes.

Chick-pea (Cicer arietinum L.) is the most important

pulse crop grown in India which occupies an area of abo, t :.:-

million acres, which is about three-fourths the wheat acreage

of India. The chick-pea is perhaps indigenous to the South­

east Europe. It is supposed that it was cultivated in Egypt

from the early earliest time of Christian era where it was

introduced from Greece and Italy. Its introduction into India

is of a more early date. There is a Sanskrit name and several

other names in modern Indian languages. It is considered to

have originated in the tract lying between Caucasus and the

Himalayas where from it has spread to the southern Europe,

Persia (Iran), Egypt and India. It has also been introduced

into parts of the central and southern America, Australia and

parts of Africa. Cicer includes 22 species (Index Kewensis,

1913) distributed in the Mediterranean and West and Central

Asia. In Asia minor and Egypt, they occur only in the wild

state. Cicer soongaricum is cultivated in parts of the

Western Himalayas. Grains of the two wild species C.

1 a

pinnatifidum Jaub & Spach (Avdulov, 1937) and C. montbreii

Jaub & Spach are t i n y ; those of former have angular seeds

w i t h minute sp ines on the t e s t a ; w h i l e the g r a i n s of t h e

l a t t e r have a smooth t es ta ( lynegar , 1935),

Soybean {Glycine max ( L . ) Me r r . i n b e l i e v e d t o have

o r i g i n a t e d from south-east As ia , der ived from a twiny slender

p l a n t G. ussuriensis Regal and Macck, commonly growing i n

t h i s reg ion . According to Fukuda (1933), Manchuria should be

the centre of o r i g i n since i t shows d i v e r s i t y in forms i n

t h i s count ry . Engelbert Kaemfer, a German bo tan is t whc wac ir.

Japan dur ing 1690-92, was the f i r s t t o in t roduce soybean t o

European Wor ld . The f i r s t ment ion o f soybean i n Amer ican

l i t e r a t u r e i s by Mease in 1804. General ly three species o f

Glycine are recognized, v i z . , G. ussuriensis ( w i l d soybean),

G. max ( the c u l t i v a t e d fo rm) , and G. gracilis ( in te rmed ia te

t y p e between t h e f i r s t t w o ) . I t i s b e l i e v e d t h a t G.

ussuriensis, fo rmer ly known as 6. soja, i s the progeni tor o f

t h e c u l t i v a t e d soybean ( P i p e r and Mo rse , 1 9 1 0 ) . I t i s

procumbent type w i t h t w i n i n g stems and narrow l e a f l e t s .

Seeds are sooty dark in colour and range from 1-2g. per 100

seeds, wh i le in the c u l t i v a t e d soybean the p lan t i s e rec t or

sem i -e rec t and the seed co lou r v a r i e s f rom y e l l o w , g r e e n ,

brown t o b lack. The seed weight ranges from 5-35 g. per 100

seeds.

-I e

Air Pollution and Plants

All living organisms including plants are dependent on

their environment. The environment constantly influences and

is influenced by its inorganic and organic surroundings. The

various gases and inorganic substances obtained from air,

water and soil one converted into complex organic molecules

by leaves of the plant. Presence of gaseous pollutants in the

air affect the performance of plant directly or indirectly by

inhibiting or accelerating the plant metabolism whic • may

influence its productivity.

A considerable amount of gaseous air pollutants

originating from different activities of man are released

into air which impures atmosphere. Sulphur dioxide (802)1

ozone -(O3), oxides of nitrogen (NO ) are recognised as the

most important toxic gaseous air pollutants and harmful to

the plants. Cameron (1874) observed that factory smoke which

caused disease in plants contained SOg. According to Heck et

al. (1982) crop losses due to air pollutants may reach upto

905($. They suggested that it conducting agricultural

research, air quality-agricultural plant ecosystem

interrelationship should be taken into the consideration.

Heagle (1973) reported that air pollutants alter the

susceptibility of plants to biotic pathogens like fungi,

nematodes, bacteria, etc.

2 0

It is now realised that the pollution damage is

obvious, severe and inescapable unless the violation of the

environment safety is not checked. Astanin and Blagosklonov

(1983) have given a chart for maximum permissible

concentration of harmful substances in the air over polluted

area (Table I).

Effects of airborne sulphur pollutants on plants

Airborne sulfur pollutants which affect plant 1if€ ?•

sulphur dioxide (SOg); hydrogen sulfide (HgS), artd sulj-' . c

acid (Hg SO4), and acid precipitation. The information is

mostly available on SOg, and the effects of this gas on

forest trees, horticultural plants, and lichens have been

documented. Effects of various sulphur pollutants have been

reviewed by Thomas (1952), Daines (1968), Barrett and

Benedict (1970), the US Environmental Protection Agency

(1973), Heck and Brandt (1975), Varshney and Garg (1979),

Amundson (1983), Bender et a1 (1986), Fluckinger and Younger

(1986), Benwart (1987), Bytnerowicz et al., (1987) and Kumar

and Yadav (1988).

Sulphur is an essential element for plants. It is a

constituent of the amino acids cysteine, and methionine. It

is also a constituent of the plant vitamins, thiamine and

biotin, and of other biochemical constituents such as

glutathione, coenzyme A, and cytochrome C. Normally, sulphur

2 1

TABLE 1

Maximal permissible concentrations of harmful substances in the air over polluted areas.

Pollutant Maximum permissible concentrations (mg/m )

Short term Daily

Ammonia 0.20

Arsenic

Benzine 5.00

Benzol 1.50

Carbon disulphide 0.03

Carbon monoxide 3.0

Carbophos 0-015

Fluorine 0.10

Fluorine compounds 0.03

Formaldehyde 0.035

Hydrogen sulphide 0.008

Lead

Mercury

Nitrogen dioxide 0.085

Non-toxic dudt 0.50

Phenol 0.01

Phosphoric anhydride 0.15

Soot 0.15

Sulphur dioxide 0.50

Sulphuric acid 0.30

0.20

0.003

1 .50

0.80

' o"

1 .00

0.03

0.01

0.012

0.008

0.0007

0.0003

0.085

0.15

0.01

0.05

0.05

0.05

0. 10

Short term = Emission mostly for 20-30 minutes. Daily = Average daily emission over a long period,

2 2

is taken up by plants from soil in the sulphate form and

assimilated into various compounds usually after being

chemically reduced. Sulfur dioxide absorbed from the air has

been shown to rapidly undergo oxidation to sulphates inside

plant tissue. De Cormis (1969) found that tomato plants soon

after exposure to SO2 had 98S5 of the S in the form of

sulphates.

Sulphur dioxide is emitted from various industrial

sources and the adverse effects on vegetation 11 uht

vicinity of these sources have been well documented. Some of

the industerial sources are -

1. Zinc and lead Smelters

2. Nickel and Copper Smelters

3. Iron concentrators

4. Petroleum refineries

5. Pulp and paper mills

6. Fossil fuel thermal generating stations

Estimation of the cost of air pollution damage to crops

have varied considerably. Annual loss of $ 500 million have

been estimated in the United States from air pollution injury

to crop plants with approximately one third of this total

loss attributable to SOj injury.

2 3

The first visible evidence of SOp injury to plants is

discernible in the foliage. The stem, bud, and reproductive

parts of the plants are visibly more resistant to SOg. The

effects of airborne sulphur pollutants on plants may be

divided into three categories: acute, chronic, and subtle

(physiological and biochemical). Sulphur dioxide enters

leaves mainly through the stomata and is toxic to the

metabolic processes taking place in the mesophyll cells.

Acute injury is caused by a rapid accumulation of b-.sulp' "'t'

and sulphite. When the oxidation product, sulphate,

accumulates beyond a threshold value that the plant cells can

tolerate, chronic injury occurs. It is estimated that

sulphate is about 30 times less toxic than sulphite (Thomas,

1951 ).

Acute injury is macroscopic necrotic injury to plant

tissue variable within hours or days after exposure to short-

term (less than 24 h) high concentrations of SOg. Acute

injury to broad leaves takes the form of lesions on both

surfaces, usually appearing between veins, and often more

prominent toward the petiole and injury is local. The

metabolic processes are completely disrupted in the dead or

necrotic areas with the surrounding green tissue remaining

functional. In some cases, injury can occur on the margins of

the leaves. Young leaves rarely display necrotic markings,

whereas fully expanded leaves are most sensitive to acute SO2

24-

injury. The anatomical effects of acute injury on foliage can

be seen under the microscope. Initially water-soaked, flaccid

areas of diffuse, gayish-green colouration appear and the

chlorophyll appears to have diffused from the chloroplasts

into the cytoplasm. This is followed by desiccation and

shrinkage of the affected cells. The green pigments are

decomposed, and the affected cells. The green pigments are

decomposed, and the affected leaf area assumes a bleached,

ivory, tan, orange-red, reddish-brown, or otown appee

Sulphur dioxide concentrations that caused injury to

vegetation in short-term periods are listed in Table 2.

Acute injury to forest trees in the field has been

attributed to SO2 doses of 0.95 ppm for 1 h, 0.55 ppm for 2

h, 0.35 ppm for 4 h and 0.25 ppm for 8 h (Dreisinger, 1965).

For acute injury to occur, other environmental and plant

factors are important. These includes sunlight, moderate

temperature, high relative humidity, adequate soil moisture,

and plant genotype and the stage of growth. Katz and McCallum

(1939) subjected various plant species to different SOg

concentrations over a number of exposure periods. The

threshold for injury was found to be 0.3 ppm SO2 for 8 h for

western larch {Larix occidental is) and 0.14 ppm SO2 for 12 h

for Douglas fir {Pseudotsuga taxifolia). In a 1-hr

experimental exposure Zimmerman and Crocker (1934) reported

that 0.66 ppm SO2 injured buck-wheat {Fagopyrum esculentum).

2 5

TABLE 2

Responses to sulfur dioxide - acute effects

SOp Exposure Plant response References cone, period (ppm) (h)

A-Responses to low SO2 doses

0.03 1 Injury to sensitive eastern Costonis (1971) white pine

0.025 6 Injury to sensitive eastern Houston (1974) white pine

B- Responses to medium SO2 ooses

0.25 1 Injury to eastern white pine Berry (1967)

0.25 2 Injury to eastern white red Berry (1971) and jack pines

0.25 2 Injury to Virginia, short Berry (1974) leaf, slash,and loblolly pines

0.25 4 Injury to broccoli Tingey et a1. (1973)

0.66 1 Injury to buckwheat Zimmerman and Crocker (1934)

0.95 1 Injury to foliage of forest Dreisinger trees (1965)

0.70 1 Injury to forest trees under Dreisinger and sensitive environment McGovern (1970)

0.3 8 Injury to weastern larch Katz and McCallum (1939)

C-Responses to high SO2 doses

2.0 2 Injury to 10 of 87 native Hill et a1. desert species (1973)

2.0 4 Injury to 10 weed species Benedict and Breen (1955)

3.0 1 Injury to Acacia pruinosa O'Conner et al ( 1974 ) .

2 6

Acute injury was produced on foliage of trembling aspen

{PopuTus tremuToides) in artificial fumigation with 0.35 ppm

SOg for a period of 3 h. Moderate to severe injury to several

Kentucky bluegrass cultivars (Poa pratensis) in artificial

fumigation of 0.2 ppm SOg for 2 h was observed

The acute effects referred to above may be considered

responses to medium doses of SOg. In the literature there are

reports of responses of plants to much lower arc to

substantially higher SOg doses. In artificial fumigation

experiments SO2 doses as low as 0.3 ppm for 1 h (Costonis,

1971) have been reported to injure extremely sensitive

strains of eastern white pine; and conversely SO2 doses as

high as 2.0 ppm for 2 h (Hill et al., 1973), have been found

to be required in order to injure tolerant plant species as

Acacia pruinosa, several native desert plant species, and

several chrysanthemum varieties respectively. Khan (1989)

found browning and chlorosis in leaves of egg plant, tomato

and okra induced by the SOp specially at 0.2 ppm.

Chronic injury is macroscopic chlorotic injury

(sometimes changing to necrotic injury) to plant tissue

usually developing over a long period of time (from over a

day to 1 or more years) from exposure to variable

concentration of SO2. Long term chronic effects on trees are

related to variety of SOg exposures which includes short-term

high concentration, short term and long-term periods of

2 T

sublethal concentrations, and even SOp-free periods when the

plant life can recuperate by translocating and assimilating

accumulated sulphur. To correlate chronic effects on forest

trees with atmospheric SOg levels, it is preferrable to use

the average concentration for the total period of exposure,

rather than the average of SO2 fumigation periods only. The

U.S. Environmental Protection Agency (1973) has concluded

that many short-term high concentration episodes were

responsible for the injury and growth reductions to occur in

the vicinity of an iron ore concentrator that emitted onl>

about 10 tons of SO2 daily. Although vegetation injury was

severe in the immediate vicinity of the plant, SOg damage

extended for only a little more than 2 km from the source

(Guderian and Stratmann, 1962). Linzon (1958a) observed that

three large nickel and copper smelters that discharged about

6000 tons of SO2 daily into the atmosphere, caused severe

damage to pine forest with both acute and chronic effects

occurring to a distance of about 25 km miles. Beyond this

distance the condition of white pine improved rapidly when

the concentration of SOg were lower than 0.25 ppm. Chemical

analyses of vegetation in the area showed the accumulation

and build-up of sulphur in foliage in vegetation growing

close to SOp sources. Both high and low concentration

fumigations of SOp over varying periods of time contributed

to the accumulation of sulphur in conifers which lead to the

development of chronic injury in older needles. In

2e

Czechoslovakia occurrence of moderate chronic injury to

foliage of spruce trees, under the influence of an average

concentration of SOg of 0.019 ppm was observed. Epiphytic

lichens which are perennial and evergreen are extremely

sensitive to SOg because they are continually exposed to the

gases in a polluted environment. In a study conducted by

LeBlanc et al. (1972), the number of epiphytes found growing

on balsam poplar (PopuTus balsamifera) trees was drastically

reduced in zones where the growing season mean levels o-f Op

were over 0.02 ppm and slightly reduced in zones where tht

mean levels of SO2 were over 0.01 ppm. Similarly Skye (1964)

found that the survival of lichens was less in areas with an

annual SO2 concentration of approximately 0.015 ppm.

Chronic injury appears as a yellowing or chlorosis of

the leaf, sometimes from lower to upper surfaces on broad

leaves. Occasionally only a bronzing or silvering will occur

on the under surface of the leaves. The rate of metabolism is

reduced in leaves displaying chronic injury. Chronic injuries

develop slowly on coniferous perennial foliage, with the

greatest increase injuries in the Sudbury sulphur-fume

effects area occurring on the 1-year-old needles of eastern

white pine trees. Continued chronic injury to perennial

foliage of coniferous trees results in premature needle

abscission, reduced radial and volume growth, and early death

of the trees. Table 3 lists the SOp concentrations causing

chronic injuries.

2 9

TABLE 3

Responses to sulphur dioxide - chronic effects

Plant response References SO2 Cone. (ppm)

Exposure period

0.07 3 days

0,

0,

0,

0,

0,

0,

0,

.076

.05

.067

.035

.008

.015

.016

14 days

24 days

26 weeks

Anuual avr. (5 months growing period)

10 year avr. (5 m. growing season)

Annual avr.

Annual avr.

Injury to sensitive eastern white pine

Injury to barley

Injury to beech

Depressed yields of ryegrass of 52X

Injury to eastern white pine in field

Banfield (1972)

Mandl et a7. (1975) Keller (1976)

Bell and '"'•c t 9I1 (1973)

Roberts (1976)

Slight injury to old foliage of eastern white pine trees in forest

Reduction in lichens and bryophytes in field

Skye (1964)

Very low diveristy in Gilbert (1969) lichen and bryophyte species in the field

0.02 Growing season avr,

Epiphyte species drastically reduced in forest.

Le Blanc et a7, (1972).

3 0

S u b t l e e f f e c t s a re measured by p h y s i o l o g i c a l o r

b iochemica l changes, and/or r e d u c t i o n i n p l a n t g row th or

y i e l d i n t h e absence o f m a c r o s c o p i c i n j u r y . E a r l y

i n v e s t i g a t o r s s tudy ing the e f f e c t s of SOg on vege ta t ion in

Europe concluded t h a t i n v i s i b l e i n j u r y , o r p h y s i o l o g i c a l

d is turbances or e f f e c t s on the growth or y i e l d s of p lan ts

cou ld occur i n the absence o f v i s i b l e mark ings ( S t o k l a s a ,

1923). Th is theory was r e f u t e d by s e v e r a l •* r v e s t i g e f ' o n s

c a r r i e d out i n North America in the 1930s (H- 1 a id " HomHt

1933; Katz e t a7 . , 1939). These i n v e s t i g a t o r s found t h a t non-

mark ing c o n c e n t r a t i o n s o f SO2 e m i t t e d under c o n t r o l l e d

c o n d i t i o n s f o r long p e r i o d o f t i m e d i d no t a f f e c t ca rbon

d i o x i d e a s s i m i l a t i o n , s t o m a t a l b e h a v i o u r , c h e m i c a l

compos i t i on or the r a t e o f g rowth o f t he exposed p l a n t s .

Davis (1972) found no y i e l d loss from soybean unless there

were v i s i b l e man i fes ta t i on r e s u l t i n g from SOg fum iga t i ons .

Subt le e f f e c t s w i thou t microscopic v i s i b l e i n j u r y t o p lan t

t i s s u e s , have been repor ted i n other i n v e s t i g a t i o n s , Bennett

and H i l l (1974) found t h a t subnecrot ic p o l l u t a n t exposures

could repress pho tosyn the t i c ra tes . Table 4 l i s t s the r e s u l t s

o f exper iments conducted t o d e t e r m i n e t he o c c u r r e n c e o f

sub t l e e f f e c t s on p lan ts in the presence of c o n t r o l l e d SOg

doses. Table 5 d i f f e r e n t i a t e s t h e t h r e e t y p e s o f p l a n t

e f f e c t s (acute , chron ic and sub t l e ) caused by SO2•

3 1

TABLE 4

Responses to sulfur dioxide - subtle effects

SOg Exposure Plant response References Cone. period (ppm)

0.25 1 hr. 2% depression in COg Bennett and Hill uptake by alfalfa (1974)

0.5 1 hr. 2^% Depression in COg uptake by alfalfa

0.7 1 hr. Increased amino acids, Godzik & Linskens decreased protein synth- (1974) esis in bean.

0.71 1 hr. 55% inhibition of pollen Masaru et a7. tube length of lily (1976)

1.0 30 min Reduced chlorophyll in Constantinidou cotyledons of red pine et a7. (1976)

0.5 2 hr. Reduced chlorophyll in cotyledons and decreased dry weight of primary needles of red pine

Ambient 187 days Ryegrass grown in water Bleasdale(1973). air scrubbed air with

98-100% of SOg removed had 48% more dry weight than plants grown in polluted air.

0.067 26 weeks Decreased yields of Bell and Clough ryegrass by 52% (1973). (Chlorosis of leaves but no lesions)

0.05 31-60 Decreased photosynthe- Keller (1976) days sis in Scot pine

0.05 141 days Decreased pollen germination in white fir.

0.05 9 months Increased peroxidase activity in spruce needle homegenates.

TABLE 5

3 2

Differentiation between three types of plant effects caused by SOg

Acute effects caused by high concentrations of SOg during short-term exposure (less than 24 h)

Chronic effects caused by variable cone, of SOg.Usually over a long period of time.

Subtle effects caused by variable concentrations of SOo.

Necrotic lesions on foliage of the current year

Chlorotic markings on foliage, some­times developing to necrosis, on perennial conifers usually on foliage older than current year

No foliar markings

Folair lesions appear within hours or days after exposure

Foliar injury usually May be possible to develops slowly over measure effects on a long period of time physiological

processes photosynthes i s, respiration, and transpiration; on biochemical processes-enzyme activities and chemical composi­tions; on pollen tube elongatin; or on pollen germination

May cause reduction in growth and loss in yield

Rarely result in plant mortality unless from recurring acute fumi gations

May cause reduction growth and loss in yield

May cause reduction in growth and loss in yield

May result in plant mortality from slowly developing injuries (especially on perennial conifers and lichens)

No plant mortality

3 3

Studies conducted in England repor t losses i n y i e l d s of

S23 ryegrass [Lolium perenne) reported t h a t ryegrass p lan ts

exposed to ambient a i r in one glasshouse weighed between 16

and 575S less than p l a n t s grown in s i m i l a r a i r i n a n o t h e r

glasshouse tha t had 98 to 100^ of the SOj removed by water

scrubb ing. Ke l l e r (1976) introduced the term ' l a t e n t ' f o r

sub t l e e f f e c t s and reported the resu l t s of long- term exposure

to a low concent ra t ion of 0.05 ppm SO2. The e f f e c t s inc luded

decreased photosynthesis of Scots pine ('^ je sy''^•est f ic],

decreased po l len germinat ion in white f i r {Abies alba), and

inc reased perox idase a c t i v i t y of need les homogenates o f

spruce iPicea excelsa). Godzik and Linskens (1974) found an

inc rease i n the t o t a l amount o f f r e e amino a c i d s and a

concurrent reduct ion in p ro te i n synthes is i n pr imary leaves

o f Widusa bean {Phaseolus vulgaris) when a r t i f i c i a l l y

fumiga ted w i t h 0.70 ppm SOg • Some o f t he e f f e c t s were

o b s e r v e d a f t e r o n l y 1 h o f f u m i g a t i o n and b e f o r e t h e

occurrence of v i s i b l e i n j u r y . Subtle e f f e c t s of SOp have been

repor ted on po l len tube e longat ion in v i t r o s t u d i e s .

Reiner t et al. (1980) found t ha t growth of soybean was

i n h i b i t e d by exposure to S02 at the concent ra t ion of 25 ppm,

when p lan ts were exposed f o r 4 h three t imes per; week f o r 11

weeks. The main e f f e c t of SO2 was a reduc t ion of shoot dry

weight at 7th week and t o t a l p lant growth a t 11th week. Kress

et al. (1986) exposed soybean p l a n t s t o i n t e r m i t t e n t SO2

3 ^

fumigations (4 h a day, 3 days a week) from shortly after

emergence untill maturity. About 7% yield losses due to 0.10

ul/L of SO2 in intermittent exposures was observed. Foliage

of many cultivars of soybean were sensitive to SOg, but the

amount of injury varied with cultivars. The point of attack

of sulphur dioxide in grasses (Benedict or Breen, 1955b;

Brennan et al., 1970; Bell and Clough, 1973; Cowling and

Lockyer, 1976; Bell, 1982) and in pines (Karpen, 1970; Berry,

1971; Roberts, 1976) is the tip of foliage w»'ich becomes

reddish brown followed by necrosis in contrast to the broad

leaved plants where the symptoms may appear anywhere on the

leaf.

Susceptibility and resistance of plants to SOg

Different plant species and varieties, and individuals

of the same species, may vary considerably in their

sensitivity or tolerance to SOp. Crop plants are classified

into three resistance groups according to their tolerance

limits. Clover-type fodder plants were most sensitive to SOg;

wheat, leafy vegetables (excluding cabbage), beans,

strawberries, and roses were moderately sensitive; and root

crops and cabbage were least sensitive. Ruston (1914)

reported that SOp caused a marked increased in soil acidity,

reducing the number of soil bacteria. Jones Eustace (1952)

observed the disappearance of lichens in heavily polluted

atmosphere which was another early report of disturbed plant

3 5

population due to air pollution. Miller et al. (1974) found

that foliage of many cultivars of soybean were sensitive to

SOrt but the amount of injury varied with the cultivar.

Reinert et al . (1980) found the growth of soybean was

inhibited by exposure to 25 ppm of SO2 when plants were

exposed for 4 h, three times per week for 11 weeks. The main

effect of SOg were a reduction of shoot dry weight at 7th

week and total plant growth at 11th week. SOg contributed to

the reduced growth in soybean in the absence of visible SO,-,

injury. Sprugel et al. (1980) observed that soybean plant

were relatively sensitive to elevated SO2 concentrations that

occurred near a point source. Reinert et al. (1982) found

that marigold shoot and root dry weights were decreased when

plants were exposed to 0.3 ppm SOg. It reduced dry flower

weight too. Sheng et al. (1988) exposed soybean cultivars to

0.7 ppm SOg which resulted in reduction in net photosynthesis

and stomatal conductance and all the cultivars developed

typical SO2 symptoms during or after fumigation.

Physiological and biochemical effects of SOg on plants

The manner in which SOp affects the metabolism of the

plant is not well understood. At the level of the plant, or

the plant leaf, the metabolic process of primary interest is

photosynthetic carbon dioxide fixation. Since 90 to 95% of

the dry weight of plants is derived from this process

(Zelitch, 1975), the impairment of photosynthesis has been a

popular explanation for plant growth reduction caused by SOg.

3 6

Different plant species have different capacities to remove

SO2 from the surrounding air (Jenes et a1., 1976). Lucerne

was found to be susceptible to SOg only if the stomata were

open. This has been confirmed by numerous investigations

since then and it is generally accepted that the primary

factor controlling SO2 uptake by plant leaves is the degree

of opening of the stomata. Generally, drought is considered

to be protective of the plant since the stomata close during

this condition. An initial increase in transpi rat .o- has .le

noticed during SOg exposure Weigl et al., 1962. Sulphur

dioxide may also react with chemical compounds making up the

cuticle and thus change the cuticular resistance. It has

been suggested that SO2 stimulates the production of waxes.

From scanning electron micrographs it cah be seen that SOg

alters the surface of confier needles. The inhibition of

photosynthesis is often regarded as the first stage of SO2

action on plants. In short-term fumigation the most sensitive

lichen species yet studied is Lobaria pulmonaria, whose

photosynthesis was inhibited after exposure to 0.5 ppm SO2

for 14 h. SO2 injury increases respiration rate of the

affected plants, the rate of respiration increases initially

in pine and spruce plants exposed to SO2.

Combustion of sulphur-containing fuels yields SO2 in

quantities 40 to 80 times that of SO3 (U.S. Dept. of Health,

Education and Welfare, 1969). Sulphur dioxide is oxidized in

3 T

the atmosphere catalytically or photochemically. The photo-

oxidation rate of SOg in air and sunlight is between 0.1 and

0.2% h. The SO3 molecules combine with water vapour in the

air to form sulphuric acid (H2S0^) aerosols. Acid smog injury

to vegetation observed in Los Angeles was described by Thomas

et a 7. (1952). Spots were formed on the upper surface of the

leaves which later extended throughout the leaf. In the

Scandinavian countries, the north-eastern United States, acid

rain has been found to have had serious implications with

respect to increasing the acidity of lakes and reducing f-'sh

populations. It has been postulated that decreased

productivity of forests in susceptible region in Sweden is

attributable to natural rainfall acidified by industrial

emissions. Wood and Bormann (1974, 1975) and Wood (1976)

reported foliar tissue damage of yellow birch (Setu/a

al leghaniensis) seedlings, using artificial acid mist of pH

3.0, and significant growth decrease at pH 2.3; increased

foliar leaching of potassium, magnesium, and calcium from

sugar maple (Acer saccharum) and pinto bean seedling using

artificial acid mists of pH 4.0, and tissue damage at pH 3.0;

and a 205K increase in growth of eastern white pine seedling

subjected to artificial acid rain at a pH of 2.3 compared to

rains with higher pH. However, soil acidity increased, and

magnesium, calcium and potassium cations were leached from

the soil at the low pHs.

3a

Sulphur dioxide after its absorption through stomata

accumulates into intracellular spaces. A large amount of SO2

can be absorbed by the cells of the leaf without any injury

if the absorption is slow and the concentration of the gas is

low. However, SO2 accumulates faster than it can be oxidised

and assimilated thus, exceeding the threshold level, and a

phytotoxic concentration presumably develops in the

intercellular spaces of the leaves, causing injury (Katz,

1952; Thomas, 1961). The excess SOg, accumulatea in ,n».

intercellular spaces, comes in contact with the water bathed

cell walls of the surrounding tissue to form sulphurous acid

and sulphates, leading to plasmolysis and collapse of the

cell (Brandt and Heck, 1968). Haselhoff and Lindau (1903)

believed that the gas reacts with aldehydes and sugars to

form secondary products which slowly release sulphurous or

sulphuric acid causing injury to the cell. However, the idea

could not last long, since the leaves are more sensitive to

SO2 in morning when the sugar content is low (Treshow and

Pack 1970). SO2 inactivates iron in the chloroplast causing

interference with its catalytic properties in assimilation.

This promotes secondary processes and break down the

chlorophyll, ultimately killing the cells. Dorries (1932)

observed that the absorbed acidity could decomposed

chlorophyll, liberating magnesium and forming pheophytin;

which may lead to chlorosis and reduced photosynthesis.

According to Thomas et al. (1943), the toxicity of sulphurous

3 9

ac id i s r e l a ted p r i m a r i l y t o i t s reducing p roper t i es ra the r

than t o i t s a c i d i t y because i t i s 30 f o l d s more t o x i c than

s u l p h u r i c a c i d . Excess of sulphate may i n t e r f e r e w i t h ion

a b s o r p t i o n , l e a d i n g t o d i s r u p t i o n i n n u t r i e n t b a l a n c e .

B leasda le (1952) found t h a t n o r m a l l y an e q u i l i b r i u m i s

mainta ined between su lphydry l group and more ox id ized su lphur

compounds such as s u l p h i t e s . Any i m b a l a n c e i n t h i s

e q u i l i b r i u m , as might be caused by an excess o f o x i d i z e d

s u l p h u r compounds, would upset s u l p h u r u t •»'"'• ?.t-c.- and

p r o t e i n syn thes i s . Sulphur d iox ide would reo-v^e t «= s u l p h i t e s

t o s u l p h y d r y l , caus ing an a c c u m u l a t i o n o f t he l a t t e r and

d i s t u r b i n g the r a t i o between su lphydry l t o ox id ized sulphur

compounds. The su lphydry l compounds thus becomes a products

o f a d i s t u r b e d su lphu r me tabo l i sm, and t h e t o l e r a n c e o f

p l a n t s t o SOg may be a f u n c t i o n o f t h e s t a b i l i t y o f

s u l p h y d r y l (Dekok et al., 1982) . Benne t t e t al. (1973)

observed t h a t r a te of uptake of gaseous p o l l u t a n t s i n t o a

l e a f depends on seve ra l p h y s i c a l f a c t o r s . Be fo re b e i n g

capable to cause i n j u r y w i t h i n the p lan t c e l l , the p o l l u t a n t

has f i r s t t o enter the s o l u t i o n in the e x t r a - c e l l u l a r water

conta ined in the c e l l w a l l . The simple s o l u b i l i t y in water i s

t h e r e f o r e , l i k e l y t o assume importance wh i le cons ider ing two

p o l l u t a n t s which d i f f e r markedly in s o l u b i l i t y and are taken

up a t d i f f e r e n t r a t e s by the p l a n t s (Law and M a n s f i e l d ,

1982). MacCormick (1968) observed tha t the e f f e c t of SOg in

" d a i l y c y c l e " i s more in the morning (7-10 A.M.) and i n the

-4-0

evening (7-10 P.M.). This diurnal change in sensitivity

corresponds to the diurnal changes of stomatal aperture in a

number of plants. During the "seasonal cycle" the effect of

SOg is more during winter than in summer (MacCormick, 1968).

Experiments under two light regimes depicting winter and

summer have proved that 505»i reduction in shoot dry weight was

obvious when SO2 fumigation accompanied winter lights

(Davies, 1980).

Nematode Parasites of Pulses

Pulses has been found to be attacked by a number of

nematodes and their pathogenicity have been proved (Gupta et

a/., 1986; Kinloch, 1980;2 Mujib et al., 1988; Patel et a/.,

1988: Chavda et al., 1988; Nath et al., 1979; Mani et al.,

1984; Rodriguez-Kabana et al. , 1981; Herman et al., 1988;

Routary et al., 1986; Wrather et al., 1988; Kinloch et al. ,

1987; Sobun et al., 1979; Dhanger and Gupta 1983; Srivastava

et al., 1974, Upadhyay and Swarup, 1981; Singh and Gill,

1990). The important nematodes which are usually found in

association with the roots of soybean and check-pea are

Heterodera glycines, Pratylenchus brachyurus, Tylenchorhyn-

chus spp., Tylenchus spp., He 1icoty1enchus spp.,

Hirschmanie 1 1 a spp., Roty1enchu 1 us reniformis, and

Meloidogyne spp.

Kinloch (1980) reported that the most widespread and

damaging nematodes in soybean production are Meloidogyne

A- 1

incognita ( K o f o i d & W h i t e ) C h i t w o o d and soybean c y s t

nematode, Heterodera glycines Ich inode, Rodriguez-Kabana et

al. (1981) observed tha t M. arenaria (Neal) Chitwood and M.

incognita p r e v a l e n t i n sandy s o i l s can s e v e r e l y l i m i t

soybean, Glycine max ( L . ) Mer r . y i e l d s . Wrather and Anand

(1988) found t h a t soybean seed l ing growth was i n h i b i t e d by H.

glycines i n f e c t i o n and soybean s e n s i t i v i t y t o the nematode

seemed t o d i m i n i s h w i t h the age o f p l a n t . K i n l o c h et al.

(1987) conducted a f i e l d t r a i l w i t h 39 soybean cu l t -var .9 and

5 breeding l i n e s a t s i t e s i n f es ted w i th M. arenaria. Y ie las

o f a l l c u l t i v a r s were too low t o j u s t i f y t h e i r p l a n t i n g in

s i t e s h e a v i l y i n f e s t e d w i t h M. arenaria. Herman et al.,

(1988) observed t ha t M. incognita suppressed shoot growth of

soybean even t h a t which was c l a i m e d t o be r e s i s t a n t t o

nematode.

Mani and Sethi (1984) s tud ied the pa thogen ic i t y of M.

incognita on ch i ck -pea c u l t i v a r Pusa-209 w i t h 5 i nocu lum

l e v e l s , namely, 0 .5 , 1.0, 2 .0 , 4 . 0 , and 8.0 larvae per gram

of s o i l . They found t h a t there was a progressive decrease i n

p lan t growth as the inoculum leve l of the nematode increased.

Nath e t al. (1979) s t u d i e d the e f f e c t o f M. incognita on

ch ick -pea. They found tha t increase in the leve l of l a r v a l

i n o c u l u m o f t h e nematode r e s u l t e d i n t h e p r o p o r t i o n a l

decrease in p l an t growth, f l o w e r i n g , f r u i t i n g and b a c t e r i a l

nodu la t ion i n ch ick-pea.

-4-2

Root-knot nematodes are one of the most destructive

plant parasitic nematodes with a wide host range and thriving

in a greatly diverse habitats. Gupta et al. (1986) screened

219 varieties / lines of mung bean for their susceptibility

to root-knot nematode, M. Javanica and found none as

resistant. Mujib et al. (1988) studied effect of M. incognita

on carpet legume (Dolichos Tablab v. Tignosus), They observed

an decrease in the length, fresh weight of shoot and root as

the inoculum density of M. incognita increased and

significant reduction in growth occurred with 1000 nematode

per 500 cc soil. Out of 60 cowpea lines/germplasm screened by

patel et al. (1988) for pathogenicity of mixed population of

M. javanica and M. incognita none was found to be resistant.

Chavda et al. (1988) studied reaction of 27 varieties/lines

of greengram to a mixed population of M. incognita and M.

javanica and found that all the tested cultivars were either

moderately or highly susceptible.

Pulses and Soil-borne Fungal Pathogens

Pulses are known to suffer from number of soil micro­

organisms among which fungal pathogens causing wilt and root-

rot are of the main limiting factors in their production. The

most important ones causing severe damage to pulses are

Fusarium oxysporum f.sp. ciceris (Padwick) Chattopadhyay,

Rhizoctonia bataticola (Taub.) Butl. {=Sc]erotium bataticola

Taub, Macrophomina phased ina (Tassi) Goid.), Fusarium solani

^ 3

f . s p . pi si, F. eumartii, Pythium ultimum, Rhizoctonia sol ani,

Sclerotium rolfsii, Operculel la padwickii, Verticil Hum albo-

atrum, and Botrytis cinera.

Mani and Seth i (1985) founded f i v e p a t h o g e n i c f u n g i

v i z . Fusarium oxysporum f . s p . ciceris, F. sol ani f . s p . pisi,

Phythium ultimum, Rhizoctonia sol ani, and Macrophomi na

phaseol ina i n a s s o c i a t i o n w i t h r o o t - r o t s and w i l t o f

c h i c k p e a . Of t h e s e , F. solani i s r e p o r t e d t o cause

a p p r e c i a b l e l o s s t o c h i c k - p e a under D e l h i c o n d i t i o n s .

I n i t i a l l y the diseased p lan ts showed ye l lowing of leaves and

the s ide shoot s t a r t e d dry ing and showed c h a r a c t e r i s t i c brown

d i s c o l o r a t i o n . Uproo t ing o f such p l a n t s , showed brown

co loured , i r r e g u l a r t o round les ions on the c o l l a r reg ions .

In advanced stages, the c o l l a r got const ra ined and the p l a n t

t a p p l e d down. B h a t t i et al. (1987) observed t h a t i s o l a t e s

from w i l t e d Cicer arietinum p lan ts included Fusarium spp.

(42%), R. solani (28%). Macrophomi na phaseol ina (1756), and V.

albo-atrum (4%). Westerlaud et al. (1974) observed t h a t F.

solani f . s p . pisi, and F. oxysporum f . s p . ciceris causes

s i m i l a r ye l low ing and w i l t i n g of the chickpea shoots, but the

former caused d i s t i n c t i v e black roo t les ions and the l a t t e r ,

vascu la r d i s c o l o r a t i o n e x t e n d i n g t o the t op o f t he s h o o t .

They observed t h a t F. oxysporum f . s p , ciceris may requ i re

wounding fo r e f f i c i e n t i n f e c t i o n , but F. solani f . s p . pisi

does not . I t was found tha t F. oxysporum f . sp. ciceris was

A-A-

not seed-borne. There were evidences which showed F. solani

f. sp. pi si was seed borne.

W i l t o f ch ick-pea which i s caused by several s o i l -

borne fungal pathogens inc lud ing F. oxysporum f. sp. ciceris,

Sclerotium rolfsii, Rhizoctonia bataticola (. Macrophomina

phaseolina), and Opercalella padwicki has been repor ted by

Kotasthane e t al. (1980) t o be a l i m i t i n g f a c t o r i n i t s

p roduct ion in Madhya Pradesh. M o r t a l i t y i n the e a r l y seedl ing

stage was c h i e f l y due to S. rolfsii wh i le a t f l owe r i ng F.

oxysporum f . s p . ciceris was the major pathogen. Alvarez and

B r i n g e r (1987) i s o l a t e d F. solani f r o m c h i c k - p e a p l a n t s

showing reduced g row th , l e a f y e l l o w i n g , d e f o l i a t i o n and

premature death. There were c o l l a r and roo t l e s i o n s , but roo t

vascu lar d i s c o l o r a t i o n . Trapero-Casas and Jimenez-Diaz (1985)

i n a disease survey in 1979-81 observed t h a t ch ick-peas in

southern Spain were severely a f f ec ted by a w i l t and r o o t - r o t

complex. Symptoms included vascular w i l t or y e l l o w i n g , non­

vascular ye l l ow ing , c o l l a r and r o o t - r o t s or c o r t i c a l c o l l a r

and r o o t n e c r o s i s , and ye l low s t u n t . They f o u n d t h a t F.

oxysporum, F. soTani and M. phased ina were associated w i th

the w i l t and r o o t - r o t complex. Salmon-pigmented i s o l a t e s of

F. oxysporum induced vascular w i l t or ye l l ow ing , and redd ish-

p i g m e n t e d i s o l a t e s i nduced n o n - v a s c u l a r y e l l o w i n g and

c o r t i c a l c o l l a r and roo t necros is . F. solani and F. eumartii

induced non-vascu lar y e l l o w i n g and b l a c k c o l l a r and r o o t

-4-5

rot, M. phaseolina induced dry collar and root.~ro't.. Si may

(1989) detected Botrytis cinerea from chick-pea seedlings

showing pod and seedling-rot symptoms. Wilt of chick-pea

caused by F. oxysporum f. sp. ciceris for the first time in

India was observed in 1940 by Padwick (1941), which causes

about 10% losses in yield annually (Singh and Dahiya, 1973).

Murumkar and Chavan (1985) observed that infection of

chick-pea by F. oxysporum f.sp. ciceris resulted in reduction

in chlorophyll and increase in organic acids, polyphenols and

carbohydrates. Toxins isolated from culture filtrate of

chick-pea wilt pathogens F. oxysporum f.sp. ciceris by

Kaur et a1. (1987), caused browning and inhibition of callus

growth, and reduced free proline and soluble protein content

of cell. Wilt resistant varieties were less sensitive to

toxin. Toxin did not result in bursting of protoplast.

Primary site of action of toxins was inhibition of RNA

synthesis. Murthy and Bazyaraji (1980) observed that the

root nd shoot protein of resistant varieties contained

higher amounts of total alkaloids than the susceptible

cultivar. Alkaloids were fungitoxic and accumulated at the

site of wound,

F. oxysporum f. sp. ciceris and, at a lower rate, F.

solani f.sp. pi si were detected inside chick-pea seeds. F.

oxysporum f. sp. ciceris reaches seeds by systemic pathway

varying for each studied line, while F. solani f.sp. pisi

was traced only to the stem and plant collar (Conci et a/.,

1985).Sharma and Gupta (1986) noted that chlamydospores of

F. oxysporum f.sp. ciceris remained viable throughout the

high temperature of the summer month during the monocropping

period in naturally infected roots of Cicer arietinum at soil

depths of 5,10 and 15 cm. The fungi did not survive in roots

placed on the soil surface.

The ubiquitous sclerotial fungus Rhizoctonia bataticola

in its pycnidial state is known as Macrophomina phaseolina.

The fungus causes complex disease syndromes like charcoal rot

of stem, root-rot, seedling blight, foliage blight, tuber

decay, dry rot, fruit rot, pod nd seed rot in several crops.

In absence of host plant, it survives or over seasons

predominantly as small black sclerotia in diseased plant

parts or in soil. /?. t>atat7co7a from different host species

differ in their morphological and cultural characters and

even differences occur in the isolates from various parts of

the same host (Jain et a7., 1973; Dhingra and Sinclair,

1973; Ghosh and Sen, 1973; Grover and Sakhuja, 1981; Hooda

and Grover, 1982; Byadgi and Hedge, 1985). M. phaseolina is

an important pathogen of many hosts like lima bean (Andrus,

1938), Jute (Varada Rajan and Patel, 1946), black gram (Tarr,

1954), sesame (Meiri and Solel, 1963), soybean (Gangopadhyay

et al. , 1970) and sweet potato (Stevens et al. , 1987). The

location of pathogen in the seeds decides the disease

-4-7

severity. Firm establishment of the pathogen within the seed

tissue is pre-requisite for its effective transmission.

Widespread losses at different stages of soybean growth

are caused by species of Col 1etotrichum, Rhizoctonia,

ScTerotium, Macrophomina, and Fusarium (Perera, 1985). Sharma

and Bhowmik (1987) observed that M. phaseoT i na (=f?.

batati col a) infection caused both quantitative and

qualitative damage to groundnut seeds. It rerultcc' •'. r

characteristic discoloration of pod and kernel, anc a mar»•

reduction in pod and kernel yield, shelling percentage and

oil content. Prinsloo (1986) noted that M. phaseolina caused

symptom of black root-rot on chicory only when roots were

tooth-pick-inoculated in the laboratory. M. phaseolina caused

symptoms only when the roots were injured by Thielaviopsis

basicola. All the cotton cultivars test by Lee et al. (1986)

were susceptible to isolates of M. phaseolina from Phaseolus

vulgaris, cotton and groundnut. The groundnut isolate (M14)

was the most virulent on cotton and mechanical wounds were

not necessary for infection. The stele portion of the tap

root and pith in the lower portion of the main stem and root

were discolored, varying from rust-brown to black. Sclortia

of the pathogen were found in the pith and the organism could

be isolated from the stele. All the soybean cultivars tested

by Garica et al. (1985) were found to be susceptible to

Sclerotium r o l f s i i , Fusarium spp., R. solani, and M.

-4-3

phaseol ina. Anahosus and Naik (1986) observed that M.

phaseolina colonizes in root and stalk of sorghum leading to

disintegration of their tissues.

Isolates of M. phaseolina obtained from different plant

species differed in cultural characters, growth rate,

morphology of the sclerotia, pycinidia and pycinidiospores,

and virulence. Bean, chick-pea and cowpea isolates were the

most virulent (Byadgi and Hegde, 1985). Raut and Ingle (1989)

observed variation between the isolates of R. batat ico'

collected from different cultivated crops belonging to seven

families. Differences were abundant even between the isolates

of crops belonging to same family. Chitima et a1. (1987) also

observed differences in morphology, growth rate and

pathogenicity among isolates of M. phaseolina and also to

some extent between individual conidia originating from a

single pycnidium.

Prasad (1986) concluded that incidence of root and stem

rot disease of jute caused by M. phaseolina was inversely

proportional to K levels. Maximum disease was observed at 0

Kg Potash/ha. and minimum of 70 Kg potash/ha. In pot culture

experiments conducted by Sharma and Chaudhary (1985) it was

observed that application of 120, 80 and 40 Kg/ha. of N, P2

Og and Kg 0 respectively were the best for the reducing

mortality of cauliflower seeding suffering from wilt and root

rot caused by R. solani and R. bataticola {M. phaseol ina).

^ 3

Losses caused by s o i l - b o r n e f u n g i , p a r t i c u l a r l y M.

phaseol ina and F. oxysporum f . s p . vasinfectum, were

est imated a t cost $ 481593 over 27000 ha. of co t ton i n 1982

(Delgado and Agurto, 1984).

In teract ion of Sulphur Dioxide and Plant Parasites

Ef fec t s of SOg on the r e l a t i o n s h i p between p lan t host

and v a r i o u s p l a n t pathogens have been examined bo th i n

ambient cond i t i ons and a r t i f i c i a l t reatments . Hegale (1973,

1982) Treshow, (1965) summarized the interact ions- oetween

severa l a i r p o l l u t a n t s i nc l ud ing sulphur d i ox ide , and hos t -

p a r a s i t e r e l a t i o n s h i p s .

The re a r e a number o f p o s s i b l e h o s t - p a r a s i t e

i n t e r a c t i o n e f f e c t s t h a t may occu r when a p o l l u t a n t i s

i n t r o d u c e d i n t o a p a r t i c u l a r h a b i t a t . The s e v e r i t y o f t h e

p a r a s i t i s m may be increased or decreased as a r e s u l t o f the

a c t i o n o f the p o l l u t a n t on the v i ru lence of the pa ras i t e or

on the s u s c e p t i b i l i t y of the hos t .

Fungal Plant Pathogens and Sulphur Dioxide

E f f e c t s o f SOg on f u n g a l d i s e a s e o f p l a n t s a r e

summarised in Table 6. Fungi may be a f fec ted by SO2 d i r e c t l y

or i n d i r e c t l y through some e f f e c t upon l i v i n g or dead p lan t

t i s s u e s , s o i l , o r w a t e r . S u l p h u r d i o x i d e r e s u l t s i n

a c c u m u l a t i o n o f s u l p h u r , i n c r e a s e d a c i d i t y and o t h e r

a l t e r a t i o n s in p lan t physio logy and b iochemist ry .

TABLE 6

Interaction of sulphur dioxide and plant pathogenic fungi

5 0

Fungal plant pathogens Host Dose

Puccinia graainis Wheat ftsbient

Effect Reference

Johanson,i954

Scheffer and HedgcQck, 1955

Scheffer and Hedgcock, 1955

Kundela and Novakovj. 1962

Skye, 19tn'

Scheffer and Hedgcock, 1955

Jancarik, 1961

Chiba and Tanaka, 1968

Sevan and Sreenhalgh, 1976

Linzon, 1958; Scheffer and Hedgcock, 1955 Sharp, 1967

Oonaubauer, 1968 Jancarik, 1961; Kundela and Novakova, 1962

Linzon, 1958; Scheffer and Hedgcock, 1955

Puccinia sp.

Hypodersella sp.

Lophoderaiua piceae

Hysteriue pulicare

Helaapsora sp.

Traaetes serialis and r. heteroaopha

Trees Aabient

Aabient

Aabient

Alder Aibient and Brich

Atbient

Trees Anbient

Rhiiosphaera kalkhoffii Red pine Aabient

Rhytisaa ocerinua

Cronatriua sp.

Puccinia striiforais

Sycaiarea Aabient

Trees Aibient

Atbient

f^raillaria aellea Trees Aabient

Coleosporiua sp. Trees Aabient

Less disease incidence

Decrease in disease incidence

Decrease in disease incidence

Increase in disease incidence

Decrease in disease incidence

Increase in disease incidence

Increase in disease incidence

Increase in disease incidence

Decrease in disease incidence

Decrease in disease incidence

Decrease in geraination of uredospores

Increase in disease incidence

Decrease in disease incidence

Table 6 Contd.

5 -I

Fungal plant pathogens Host Dose Effect Reference

Uroayces phaseoli Bean 0.13 ppi for 24 h/d Decrease in pustule Weidensaul (on 8 days before or nuiber, spore size and Darling, 1979 7 days after inocula- spare size and geri-tion) ination

Scirrhh acicola Scots 0.20 ppi for 6 h 5 pine days after inocula­

tion

Increase in lesion Weidensaul nunber and Darling, 1979

S. acicola

Puccinia graainis

ledius

Mheat

1.0 ppa for 4 h Nortal groHth Hai, 1971

0.10 ppa for 100 h Decrease in lesion Laurence et ah, froB 2 days frot nuiber 1979 inoculation

mternaria sp. 50 ppa for 2 ainutes 60^ decrease in Couey, 1965 at aoist condition of spore geraination 100 ppa for 24 ainutes at 981; RH

Oiplocarpon rosae Rose 0.01 and 0.04 ppa for Diseased leaflet area Saunders, 1966 2 days after inoculation slightly increased at

at 0.01 ppa Bore than the 0.04 ppa

Penicilliua sp.

Helaintho sporiua eaydis Maize

90 ppa SO, in nutrient Slight stiaulation in Saunders, 1966 solution groHth

0.15 ppa for 14 h/d 8 Decrease in lesion Laurence et ah, days before inoculation nuaber 1979

nicrosphaera alni Lilac 0.30-0.40 ppa for 24-72 Decrease in conidial Hibben and

5 2

Genera l l y , excess o f SO2 i n the atmosphere t ends t o

d e c r e a s e t h e s e v e r i t y o r i n c i d e n c e o f h o s t - p a r a s i t e

r e l a t i o n s h i p . Rus t d i s e a s e s appear t o be p a r t i c u l a r l y

s e n s i t i v e to SOg. Johanson (1954) reported less wheat stem

rus t caused by Puccini a graminis i n an i n d u s t r i a l i z e d area of

Sweden t h a n i n non i n d u s t r i a l i z e d a r e a s . S c h e f f e r and

Hedgcock (1955) found decrease of a number of rus t diseases

caused by species o f Cronartium, Coleosporium, Melampsora,

and Peridermium, where t rees were i n j u red by SO2. We-ipctein

et al. (1975) found t h a t SOg reduced the i n c i d e n c e and

s e v e r i t y of bean r u s t disease caused by Uromyces phasedi on

p i n t o bean. Continuous exposure t o 0.13 ppm of SOg on the 8

days before i nocu la t i on or on the 7 days a f t e r i n o c u l a t i o n

caused f o l i a r i n j u r y and decreased the number of pus tu les and

the s i z e and percentage g e r m i n a t i o n o f spores produced on

exposed leaves. In genera l , ob l i ga te fungal p lan t pathogens

are more sens i t i ve t o SO2 as compared to other fungal p l a n t

p a t h o g e n s . Fungal d i s e a s e s on p l a n t f o l i a g e have been

repor ted to be reduced in incidence by atmospheric SOg i n the

v i c i n i t y of i ndus t r i es in several coun t r i es . These lea f fung i

i n c l u d e s HypodermeT 1 a laricis, Lophodermium pinastri,

Hypodermella sp. (Schef fer and Hedgcock, 1955), Lophodermium

Juniperi, Rhytisma acerinum (A i r p o l l u t i o n , 1968), Hysterium

pulicare (Skye, 1968), and Venturia inaequalis ( P r z y b y l s k i ,

1967). Kock (1935) repor ted the absence of oak powdery mildew

caused by Microsphaera alni near a paper m i l l in A u s t r i a .

5 3

Saunders (1966) observed that rose black spot disease caused

by Diplocarpon rosae was rarely present in areas where the

daily average SOg concentration was greater than 0.04 PPM.

Khan and Kulshrestha (1991) studied effect of SO2 on conidial

germination of eight powdery mildew-fungi species viz.,

Sphaerotheca fuliginea (Schlecht. ) Poll., S. cassiae Pandotra

& Ganguly, Erysiphe cichoracearum D C , E. trifolii Grev., E.

pisi D C , Microsphaera alphitoides Griff & Maubl . f. sp.

zizyphi and PhyHactinia dalbergiae Pr ioz. They observed

that all the conidia tested were sensitive to SO2 and its

germination was increasingly inhibited with an increase in

the concentration of SOg.

Effect of SO2 on parasitism by non-obligate fungal

pathogens show cases of inhibition, stimulation, or no

response. Exposures that decreased parasitism of bean by

Uromyces phaseoli did not affect parasitism of tomato leaves

by Alternaria soTani. Laurence et al. (1979) observed

decrease in number of Helminthosporum maydis lesion by 38%

when maize plants were exposed to SO2 on the 8 days before

inoculation (0.15 ppm for 14 h daily) if the exposure

occurred on the 8 days before and on the 2 days after

inoculations, the number of lesions decreased by only 13-16%,

Spores of most fungi tested appear to be very resistant to

direct exposure to SO2 and moist spores apparently are more

sensitive to than the dry ones. Couey and Uota (1961)

5-4-

observed that only 20* of the conidia of Botrytis cinerea

germinated when they were exposed to 36 ppm SO2 for about

1/2 h. But Hibben (1966) observed no effect on germination of

spores of 10 saprophytic and parasitic fungi when they were

exposed on agar to 10 ppm SO2 for 1-6 h. Couey (1965) found

that germination of wet conidia of ATternaria sp. decreased

60X from exposure to 50 ppm SO2 for 24 min but 100 ppm SO2

was required to produce a similar decrease in the dry

spores at 985K RH. Conidia of Di plocarpon rosae g' rmi n^ted

abnormally and hyphal growth was reduced in aqueoL SJIS. e

solutions that contained the equivalent of more than 35 ppm

SO2. Spores of other fungi such as Aspergillus niger and

Alternaria brassicicola were also affected but were more

resistant than D. rosae (Saunders, 1966). Germination of

Scirrhia acicola conidia suspended in water was not affected

by exposure to 0.90 ppm SOg for 6 h (Ham, 1971). Khan and

Kulshrestha (1991) found that SO2 exposure inhibited conidial

germination of a number of powdery mildews. SO2 concentration

and exposure duration were determinants of inhibition.

Some researchers have found that SOg can increase the

severity of foliar diseases. Tanaka et al. (1982) reported

that sooty leaf mold disease, Rhizosphaera klkhoffi i, was

more severe on Pinus densiflora trees that were inoculated

and transplanted to areas with high concentrations of

atmospheric SOg than on trees in areas with no air

pollution. Weidensaul and Darling (1979) observed more

5 5

les ions of Scirrhia acicola on needles of scots pine seedings

when they were exposed t o 0 .20 ppm SO2 a t 5 days a f t e r

i n o c u l a t i o n t h a n on unexposed p l a n t s . The e f f e c t was

s i m i l a r , but not s i g n i f i c a n t , when the 6 h. exposure ended 30

min . before i n o c u l a t i o n .

P lan t P a r a s i t i c Nematodes

The e f f e c t o f s u l p h u r d i o x i d e on h o s t - p a r a s i t e

i n t e r a c t i o n s i nvo l v ing roo t -kno t nematodes, has gained l i t t l e

s tudy. But, there are few evidences i n d i c a t i n g the e f f e c t of

a i r p o l l u t i o n on p lan t p a r a s i t i c nematodes (Table 7 ) . Bassus

(1968) found occurrence o f fewer numbers bu t a g r e a t e r

v a r i e t y o f nematode species i n s o i l s where t rees were damaged

by SOg. Khan (1989) s tud ied the e f f e c t of SOg, O3 and SOg-Og

m i x t u r e o f d i f f e r e n t c o n c e n t r a t i o n s on t o m a t o p l a n t s

inocu la ted w i t h M. incognita race 1. He observed t h a t SO2 and

O3 (both p a r t i c u l a r l y at 0.2 ppm) and M. incognita, ac t i ng

alone s i g n i f i c a n t l y reduced p lan t growth and y i e l d parameters

and lea f pigment content of tomato. Synergism was observed

when p lan ts were exposed t o 0.2 ppm SO2 and 0.1 or 0.2 ppm Og

and g r e a t e r r educ t i on was observed than t h e sum o f t h e i r

i n d i v i d u a l e f f e c t s . SO2 and O3 a l s o i n d i v i d u a l l y a c t e d

s y n e r g i s t i c a 1 1 y w i t h t h e nematode and caused g r e a t e r

reduc t ion i n growth parameters than the reduc t ion in nematode

inocu la ted unexposed p lants or un inoculated exposed p l a n t s .

When tomato p lan ts inoculated w i t h M. incognita race 1 were

5 6

IABLE-7

Effect of air pollution on pltnt parasitic neaatodes

Treataent

SO2

SO2

SO2

Oj and

OT and

0, and

Oj and

SO2 ' h

Oj and

0, and sBj + O3

0.2 ug O3/ lit., 0.2/ ug S02/lit. singly or in coabination

0.2 ug Oj/L + 0.8 ug SOp/L

80 ppB O3

Neaatode

Pratylenchus penetrans

Heleidogyne incognita Race 1

fi. incognita & M. javanica

Heterdora glycines

Heterodera glycicss^Rhizobiut

Beloaolaiaus longicaudatus

Paratrichodorus tinor

8. longicaudatus ^Rhiiobiut

Aphelenchoides fragariae

P. penetrans

P. penetrans

H. hapla

Host

Soyabeen

Toaato cv. Pusa Ruby

Lentil, chickpea

; Soyabeen

Soyabeen 1

Soybeen

Soybeen

Soyabean

Begonia

Toaato

Tomato

Tobacco

Effect

Enhanced reproduction of neaatode

SO2 interacted synergis-tically Mith the neaatode

Root galling suppressed

Inhibition in proouctio! and developaent or nesatode

Severe inhibition in nodulation

Unaffected

Reproduction and developaent of neaatode inhibited

Inhibition in nuaber of nodules

Decreased folior injury by neaatode

Synergistic interaction

ftntagonistic interaction

Increase in disease

References

Weber et al.,

Khan, 1989

Singh, 1989

Meber ai.,

Weber et al.,

Neber et al.

Meber et al.

Weber et al.

Weber et al.

Shew et al..

Shew et a l ,

1979

' ] -

, 1979

, 1979

, 1979

, 1979

, 1979

1982

1982

Bisessar and Plaaer 1984

Table 7 Contd.

5 -7

Treattent Nesatode Host Effect References

0.2 ug Oj/L + 0.8 9. penetrans ug SO2 L

Tosato Antagonistic interaction Shew et a l . , 1982

80 ppB Oj (anbient) H. hapla

Simulated of pH 6.0 tines Heel

h SO3+O3

SO2+O3

acid rain or 3.2, 3 dy

t

H. hapla

fi. incognita

H. incognita Race 1

H. incognita

Acid rain at pH 6.6 H. incognita before inoculation Race 1

Acid rain at pH 3.2 H. incognita after inoculation Race 1

Acid rain at pK 5 and 6

H. incognita H. javanica

Tobacco Increase in disease incidence

Kidney Decreased neiatode bean infection of pH 3.2

Bisessar and Pla«er 1984

Shriner, 1978

Lentil Root galling suppressed Singh, i

To«ato Growth of neeatode reduced Khan, 1989

Chickpea Juvenile hatching Singh, 1989 suppressed

Totato Root penetration and Khan, 1989 reproduction increased significantly

Toiato Root penetration and Khan, 198<) reproduction decreased significantly

Lentil Juvenile hatching Singh, 1989 chickpea suppressed

se

exposed to SOg + O3 mixture at 0.2 + 0.2 ppm or 0.2 + 0.1 ppm

of each pollutant respectively, synergistic reduction in

growth of nematode was observed. Hatching of juveniles of M.

incognita and M. Javanica was suppressed by exposing to SOg,

O3 and their mixture. Higher concentration of pollutants were

more suppressive than the lower concentrations, and the

effect of pollutant mixture was greater than their individual

effects. M. incognita was more sensitive to pollutant mixture

than M. javanica. Juvenile hatching of M. incognita and M.

Javanica were adversely affected by the acidity of the media

and decreased with the increasing acidity. At pH 6, greater

suppression in juvenile hatching of M. incognita was observed

whereas in acidic range (from pH 5 onwards) the suppression

in juvenile hatching of M. javanica was more than M.

incognita (Singh, 1989). Khan (1989) observed a synergistic

interaction between M. incognita race 1 and simulated acid

rain at pH 3.2 on tomato plants. They caused greater

reduction on tomato plants than the sum of reductions induced

by each individually. Root penetration and production of M.

incognita race 1 and disease intensity were significantly

increased at pH 6.6, but at pH 3.2 significant decrease were

recorded.

Weber et al. (1979) observed that non-injurious doses

of SOp failed to affect adversely four nematode parasites of

soybean viz., Pratylenchus penetrans, Be 1 one 1 aimus

5 9

longicaudatus, Heterodera glycines, and Paratri chodorus

minor, o r one nematode p a r a s i t e i n l e a v e s o f b e g o n i a ,

Aphelenchoides fragariae. However, r e p r o d u c t i o n o f P.

penetrans was increased when soybean p lants were exposed to

SO2 on the 4 days before i nocu la t i on and on 3 days per week

f o r 13 weeks a f t e r i nocu la t i on (0.25 ppm fo r 4 h d a i l y ) . This

dose of SOp was not enough to i n j u r e leave or to a f f e c t p l an t

g r o w t h . Exposure of soybean p l a n t s t o SOg enhanced t he

r e p r o d u c t i o n o f P. penetrans compared w i t h t h a t i n p ' 'an ts

exposed t o the charcoal f i l t e r e d a i r c o n t r o l . Brewer (1979)

observed t h a t r e p r o d u c t i o n o f P. penetrans on tomato was

s l i g h t l y suppressed by O3 a t 0.2 ppm but not by SOg a t 0.80

ppm (3 h/day on 2 days per week, f o r 8 weeks). However, the

mix tu re o f 0.20 ppm of O3 and 0.80 ppm of SOg caused

increased reproduc t ion of P. penetrans. Shew et a7. (1982)

conducted a s e r i e s of experiments to understand the poss ib le

i n t e r a c t i o n of P. penetrans and Oo and SOg on tomato p l a n t s .

Tomato p lan t s c u l t i v a r 'Wa l te r ' were inoculated w i th i n i t i a l

popu la t ion d e n s i t i e s of P. penetrans ranging 0-4000 nematodes

per po t and were repeated ly exposed f o r 3 h t o OQ doses

ranging 0.0 - 0.4 u l / 1 of a i r (1 ul O3/I of a i r = 1.960 ug

Og/m of a i r ) . I n another e x p e r i m e n t s , tomato p l a n t s ,

un inocu la ted or inocula ted w i th P. penetrans were exposed (4

h per exposure) 15 times to 0.2 ul O3/I of a i r , or 0.2 ul

SOg/l (1 ul SOg/l of a i r = 2620 ugSOg/m"^ of a i r ) , or bo th ,

or were exposed (3 h per exposure) to 0.2 ul O3 / I of a i r or

eo

0.8 U1S02/1 of air or both. Exposures to charcoal-fi1tered

air served as control. Decrease in dry weights of plant

parts excised from tomato plants exposed to 0.2 ulOg/l of air

added to the decrease in dry weight, caused by exposure to

SO2 at 0.2 ul/1 of air adequately predicated the decrease in

dry weight of tomato plants caused by exposure to 0.2 ulOg +

0.2 ulSOg per liter of air. When 0.2 UIO3 and 0.8 ulSOg per

liter of air were present in mixture, they acted

antagonistically and caused less change in leaf and shoot dry

weight than could be predicated by the main affects of 0^ and

SOg.

Plant Pathogenic and Nodule-forming Bacteria

Laurence and Aluiso (1981) observed that SO2 effects

the parasitism of bacteria. Table 8 shows the influence of

SO2 on some plant bacterial pathogens. It has been observed

that Corynebacterium nebraskense was inhibited when maize

plants were exposed continuously to 0.20 ppm SOg for 24

h/day, 5 days before inoculation, 2 days after inoculation

and both pre and post inoculations. However, maximum

inhibition of bacteria occurred at 2 days post-inoculation

exposure. They also observed that Xanthomonas phaseoli was

inhibited when soybean plants were exposed the 0-10 ppm SO2

for 24 h 5 days before inoculation, 5 days after inoculation

and both 5 days before and after inoculation exposures.

6 1

TABLE

Interaction of sulphur dioxide (SO.) and plant pathogenic bacteria and viruses.

Treatient Bacteria/Viruses Host Effect Reference

0.20 ppi for 24 h/day 5 days Corynebacteriut nebcaskense before or 2 days after inoculation or both

Haize Inhibitory Laurence and Aluisio, 1981

0.10 ppa for 24 h/day for Xanthoeonas phaseoli 5 days before or 5 days after inoculation

Soybean Inhibitory

0.10 ppn for 24 h for 7 days Southern bean aosaic virus Bean

Laurence and Aluisio, 1981

Increase in virus Laurence et a h , 196 conceni ratio'-

0.10 ppii for 24 h for 7 days Maize d«arf mosaic i/irus Maize IncrfcaSfc id \iruii taurciice ii, a;., i9S concentration, infection and severity of syaptoas

61

6 2

Sulphur dioxide increases the soil acidity which can

conceivably alter the progress of plant-parasite

interactions. Shriner (1974) found that kidney been and

soybean exposed over 8 weeks in the field or 5 weeks in the

greenhouse to pH 3.2 developed an average of 75X fewer

nodules than plants exposed to pH 6 treatments. Overall, 74%

of the plants that failed to nodule at all had received pH

3.2 treatments. In a time-related study, nodulation was

inhibited most by daily exposure to pH 3.2 treatments applied

15-21 days after plants were inoculated with Rhizobium.

Interaction of Sulphur Dioxide with other Air Pollutants

In nature, plants are rarely exposed to the influence

of only one air pollutants. Before 1966 some observations and

experiments had indicated that air pollutant mixture might

influence plants differently from the action of a single

pollutant.

Menser and Heggestad (1966) found that three varieties

of tobacco plant suffered from 25 to 38% leaf damage upon

exposure to a combination of 0.24 ppm SO^ and 0.027 ppm Og

for 2 h., whereas either pollutant alone at approximately the

same concentration and for the same time period caused no

injury to any of the three tobacco varieties. They suggested

that the injury to the tobacco plants was caused by a

synergistic effect of SOg and O3. The potential harm that may

6 3

be caused by mixture of low levels of SO2 and NOg was

demonstrated by Tingey et a7. (1971). A gaseous mixture of

0.10 ppm SO2 and 0.10 ppm NOg caused syngergistic effect with

greater than 5% leaf injury being induced on five of six

plant species treated in 4 h exposure periods. Bel W-3

tobacco plant displayed S% leaf injury after a 4-h exposure

to a mixture of 0.05 ppm SOg and 0.10 ppm NOg. Tingey et al.

(1973b) found that foliar injury on broccoli showed an

additive response to a mixture of 0.25 ppm SO^ • MG C 'O po-r.

O, for 4 h, whereas Bel W-3 tobacco showed & synergistic

response under the same regime. Low concentrations of SOg

and/or O3 to injured foliage of peanut plants in controlled

experiments. The response to a mixture of the two gases was

synergistic. Either 0.35 ppm SO2 alone for 3 h or 0.05 ppm O3

alone for 3 h injures the foliage of trembling aspen, a

combination of 0.20 ppm SOg and 0.05 ppm O3 for 3 h causes

more injury than the sum of the individual pollutants. White

et al (1974) reported a synergistic response of alfalfa to a

mixture of 0.15 ppm SO2 and 0.15 ppm NO2 in a 2-hr exposure

which depressed the apparent photosynthetic rate by 1%,

whereas 0.25 ppm of SOg alone or 0.40 ppm NO2 alone was

required to cause a 2% depression.

Mandl et al. (1975) studied effect of SO2, HF alone and

in mixture on barley, sweet corn, and bean plants. A

synergistic response was found to a mixture of low

6 4

concent ra t ions of two gases. Barley leaves d isp layed greater

i n j u r y in a mixed gas experiment than the sum of the i n j u r i e s

caused by the i n d i v i d u a l p o l l u t a n t i n a 27-day exposure

p e r i o d . The concent ra t ions of the po l l u tan t s u t i l i z e d were

approximately 0.08 ppm SO2 and 0.6 ug/m HF. I n t e r a c t i o n o f

su lphur d iox ide w i t h other p o l l u t a n t s on soybean are shown in

Table 9.

I n t e r a c t i o n of Nematodes w i t h o ther S o i l - b o r n e P l a n t

Pathogens

The number of s o i l microorganisms present in zhe •oo t

zone o f any crop p l a n t p rov ide s u f f i c i e n t o p p o r t u n i t y f o r

d i v e r s e i n t e r a c t i o n s . M a j o r i t y o f r o o t d i seases have a

complex e t i o l o g y (Grogan, 1981; Wal lace, 1978). Microorganism

i n the root zone may e x h i b i t cond i t ions l i k e synergism and

antagonism and may i n t e r a c t w i t h each o t h e r and w i t h t h e

hos t . Fawcett (1931) s ta ted t h a t "nature does not work w i t h

pure c u l t u r e s " and t h a t most p lan t diseases, p a r t i c u l a r l y

roo t d iseases, are in f luenced by associated microorganisms.

Root i n f e c t i o n by one pathogen may modify the host response

t o subsequent i n f e c t i o n by pathogens or saprohytes.

The t e r m i n t e r a c t i o n i s used q u a n t i t a t i v e l y and

q u a l i t a t i v e l y in descr ib ing the i n t e r r e l a t i o n s h i p between two

or more f a c t o r s i n v o l v e d i n p l a n t d i s e a s e s . Synerg ism and

a n t a g o n i s m a r e b e s t c o n s i d e r e d as t e r m s d e s c r i b i n g

6 5

TABLE 9

Effect of sulphur dioxide eixture Hitb other pollutants on soybean.

Mixture Host Treataent Effect Reference

SO.tO, Soybean 0.08 or 0.10 ppa 0^, 0.20 or Foliar injury and reduced Pratt et a l . , 1983 0.40 ppa SOji 2 or ^ h/day, chlorophyll synergistic 1-5 days

Soybean 0.067 ppa 0,, 0.30 ppa SO,; Synergistic reduction in Le Sueur-Bryaer and 7.5 h/day, 5 days COj exchange rate (CER), no Oraood, 1984

change in CER with Oj and only slight with SOj

Soybean 0.25-1.0 ppa Oj, 0.50-1.5 ppa Foliar injury and reduced Heagle and Johnstor,. (2 cultivars) SOj; 0.75, 1.5 or 3 hours shoot fresh weight additive, 197">

antagonistic or synergistic, depending upon concentration and tiae

SOj+NOj Soybean 0.2, 0.4, 0.6 ppa of each gases 2; hours

Soybean 0.18 or 0.5 ppa SO, alone (2 cultivars) or Nith 0.06 ppa NOj; 4 h/day, of NOj at loH SOj, I"

Photosynthesis: synergistic, Carlson, 1983 stoaatal conductance: synergistic, respiration: additive

Yield: no additional effect Aaundson, 1983

but 14 days

Soybean 0.13-0.42 ppa SO,, 0.06-0.40 ppa NO2; 3-hours/exposure, 10 days during pod fill (2 year study, aabient air with O3)

increase in reduction at high SO.; not designed to deteraine aixture effects

Chlorophyll reduction, synergistic; yield reduced froa 9 to 25 ; in 2 years, synergistic

Irving and Miller, 1984

6 6

q u a n t i t a t i v e p l an t disease i n t e r a c t i o n s and t h a t the combined

e f f e c t of a p l a n t p a r a s i t i c nematode and a n o t h e r p l a n t

disease organism i n e i t h e r g rea te r or less than the sum of

the e f f e c t s of the i n d i v i d u a l organisms.

Nematodes , f u n g i , b a c t e r i a , s o i l - b o r n e v i r u s e s ,

act inomycetes, e t c . are s o i l i n h i b i t i n g microorganisms and

t h e i r pa thogen ic i t y to many crop p lan ts are we l l documented.

P l a n t p a r a s i t i c nematodes a r e c a p a b l e o f c a u s i n g ' w e l l

man i fes ted d iseases on t h e i r own, bu t i n a s s o c i a t i o n w i t h

o t h e r p a t h o g e n s t h e y cause much g r e a t e r damage due to

s y n e r g i s t i c a c t i o n of i n t e r a c t i n g organisms. There are many

s t a t e m e n t s a v a i l a b l e w h i c h s u g g e s t t h a t s y n e r g i s t i c

i n t e r a c t i o n s are common and cons tan t l y degrade p l a n t h e a l t h .

Nematode and fungal plant pathogens

Observa t ions of A t k i n s o n (1892) on t h e i n t e r a c t i o n

between Meloidogyne spp. Fusarium w i l t of co t ton probably

tend t o researches on d isease comp lexes . He observed t h a t

Fusarium w i l t o f c o t t o n was a l w a y s more s e v e r e i n t h e

presence of r o o t - k n o t nematodes. Many i n v e s t i g a t o r s have

observed t h a t Fusarium w i l t o f c o t t o n caused by Fusarium

oxysporum Sch lec t . f . sp. vasinfactum ( A t k . ) Synd & Hans, was

g r e a t l y increased in presence o f Meloi dogyne i ncognita

(Mar t i n et a / . , 1956; Smith, 1948; 1948; Nor ton, 1960; White,

1962; Brod ie and Cooper, 1964; M a i e r , 1964; M i n t o n and

e 7

Min ton , 1966). P o r t e r and Powel l (1967) observed t h a t

p re inocu la t i on w i th nematodes caused a s i g n i f i c a n t increase

i n fungal i n f e c t i o n . Many i n v e s t i g a t o r s have s t u d i e d t h e

poss ib le i n t e r a c t i o n of nematodes w i t h other s o i l i n h a b i t i n g

microorganisms (Powell 1963, 1971a, 1971b; P i t che r , 1965;

Bergeson, 1972; Khan, 1984; Webs te r , 1985; Mai and Abawi

1987; Tay lor , 1991 ).

The mechanism by which M. incognita predispose co t ton

p lan ts to disease has not been f u l l y exp la ined . M. incognita

may t r a n s p o r t the Fusarium w i l t f ungus i n t o r o o t s o r t h e

fungus may invade th rough wounds made when M. incognita

enters the roots (Smi th , 1954). Caquil and Shepherd (1970)

concluded t h a t s t r ess and d e b i l i t a t i o n of seedl ings caused by

M. incognita damage may be m a j o r f a c t o r i n t h e

p r e d i s p o s i t i o n , and M. incognita i nduced g i a n t c e l l s may

a t t r a c t and/or be more e a s i l y p a r a s i t i z e d by f u n g i t han

normal c e l l s . Sidhu and Webster (1977) proposed t h a t M.

incognita may induce p roduc t ion of a t r ans loca tab le f a c t o r

or f ac to rs t h a t can predispose p l an t pa r ts d i s t a n t from the

s i t e of M. incognita i n f e c t i o n . Root s p l i t s are caused by M.

incognita (McClure et al. 1973; Shepherd, 1970) , and the

s p l i t may be avenues through which the Fusarium oxysporum f .

sp. vasinfectum and other d isease-causing organisms invade

roots (Shepherd, 1970).

6 S

Some fung i are seed-borne, t h i s i nd i ca tes tha t i n these

cases the fungus i s the f i r s t ac t i ve pathogen. S i m i l a r l y i n

t h e s e cases where f u n g i c i d a l seed t r e a t m e n t s a r e n o t

e f f e c t i v e or when non-fumigant nematicides t h a t have systemic

a c t i v i t y are used, fungus become the pr imary , and nematode

the secondary pathogen i n s e q u e n t i a l i n t e r a c t i o n s . The

inc rease i n nematode p o p u l a t i o n d e t e c t e d i n a number o f

s t u d i e s where t h e f u n g u s was t h e p r i m a r y p a t h o g e n

demonstrate the importance o f t h i s t ype o f i n t ^ e r a c t i o n s

(Mountain and Mckeen, 1962; Nordmeyer and S iko ra , 1983).

I n t e r a c t i o n s tud ies i nvo l v i ng nematodes have generally

f o l l o w e d the s e q u e n t i a l d isease complex approach wh i ch

invo lves a pr imary pathogen, the nematode, and a secondary

pathogen, the fungus or bacterium e t c . The use of sequent ia l

i n o c u l a t i o n s c o u l d mask o r p r e v e n t i n t e r a c t i o n f r o m

deve lop ing and a l t e r those a f f e c t e d by t h e r h i z o s p h e r e

p h y s i o c h e m i c a l e n v i r o n m e n t near t h e r o o t t h a t change

d r a s t i c a l l y w i t h p l a n t age (Tay lor , 1979; Webster, 1985).

Change i n root exudat ion pat te rns t ha t develop w i th p l a n t

age could a l t e r the environment and a f f e c t i n t e r p r e t a t i o n

of r e s u l t s . A c t i v i t i e s of microorganisms in the rh izosphere

and r h i z o p l a n e are g r e a t l y i n f l u e n c e d by t he q u a l i t y and

quan t i t y of root exudat ion and s loughed-of f t i ssues (Cook

and Baker, 1983). I t has been o f t e n sugges ted t h a t r o o t

exudates are a l t e r e d by i n f e c t i o n of host p lan ts by p l a n t -

6 9

p a r a s i t i c nematodes, p a r t i c u l a r l y roo t - kno t nematodes. Van

Gundy et a 7. (1977) observed t ha t exudates from M. incognita

i n f e c t e d tomato roo ts a t t r a c t e d hyphae of Rhizoctonia sol ani,

enhanced i n i t i a l s c l e r o t i a l f o r m a t i o n ; and i n c r e a s e d

s e v e r i t y o f r o o t d e c a y . Van Gundy e t a7 . ( 1 9 7 7 ) and

Melakebrahan et a 7. (1985) reported t h a t root exudates from

r o o t - k n o t i n f e c t e d r o o t s were f o u n d t o c o n t a i n h i g h e r

concent ra t ions of Ca, Mg, Na, K, Fe and Cu, as compared to

those f rom n o n - i n f e c t e d r o o t s . Root exuda tes g e n e r a l l y

accumulate near the roo t t i p , and thus the s o i l m i c r o f l o r a

are a l s o abundant and c l ose t o t h e l o c a t i o n o f e n t r y f o r

la rvae o f M. incognita and hyprae of fungus. This sec t ion of

the review w i l l concent ra te on i n t e r a c t i o n s tud ies i n v o l v i n g

nematodes e s p e c i a l l y roo t knot nematodes and w i l t causing and

roo t r o t fung i t h a t would be re levant to the proposed work.

a. In teract ion with w i l t causing fungi

The i n t e r a c t i o n between Meloidogyne spp . and w i l t

c a u s i n g f u s a r i a have been s t u d i e d more t h a n any o t h e r

nematode-fungus combinat ions (Powel l , 1963; Mai and Abawi,

1987). Mar t in et a1. (1956) were the f i r s t who conducted

t h e i r experiments i n greenhouses or growth chambers using

p a s t u r i z e d , s t e r i l i z e d , or f u m i g a t e d s o i l t o s t u d y t he

i n t e r a c t i o n between Fusarium w i l t fungus and Meloidogyne s p . .

I n t e r a c t i o n between Meloidogyne spp . and f u n g i c a u s i n g

Fusarium w i l t have been s tud ied d i f f e r e n t i n v e s t i g a t o r s on

a l f a l f a ( G r i f f i n , 1986; McGuire et al., 1958); banana (Loos,

T O

1959; Newhall , 1958); beans (R iber io and Ferraz, 1984; Singh

et al. , 1981); Cabbage ( F a s s u l i o t i s and Rau, 1969); ca rna t i on

( S c h i n d l e r e£ al., 1 9 6 1 ) ; ch rysan themum ( J o h n s o n and

L i t t r e l l , 1 9 6 9 ) ; c o t t o n ( A t k i n s o n , 1892 ; C a u q u i l and

Shepherd, 1970; Cooper and Brodie, 1933; Garber et al., 1979

Mar t in et al., 1956; Minton and Minton, 1966; Nor ton, 1960)

cowpea (Thomason et al., 1 9 5 9 ) ; mimosa ( G i l l , 1958)

muskmelon (Bergeson, 1975); pea (Davis and Jenk ins , 1963)

tobacco (Melendez and Powell , 1967; Por ter and Powel l , "^96'

and tomato (Abawi and Baker, 1984; B inde r and H u t c h i n s o n ,

1959; Bowman and Bloom, 1966; F a t t a h and Webs te r , 1983;

Goode and McGuire, 1967; Hirano et al., 1979; Jenkins and

Coursen, 1957; Jones et al. 1976; Kawamura and Hi rano, 1967;

1968; Or ion and Hoes t ra , 1974; p i t c h e r , 1978; S idhu and

Webster, 1974, 1977, 1979, 1983; Young, 1939, 1940).

Much work has been done on t h e i n t e r a c t i o n o f r o o t

i n f e c t i n g fungi w i t h endoparas i t ic nematodes i n comparison t o

semi-endoparas i t ic or e c t o p a r a s i t i c nematodes (Khan, 1984).

The i n t e r a c t i o n o f nematodes w i t h w i l t c a u s i n g f u n g i

espec ia l l y Fusarium spp. have drawn much a t t e n t i o n . (Powe l l ,

1971a, 1971b). McGuire et al (1958) s tud ied the e f f e c t of

roo t - kno t nematodes on the development of Fusarium w i l t i n

Bu f fa lo v a r i e t y of a l f a l f a . At t e r m i n a t i o n , the percentage of

p lan ts i n fec ted w i t h Fusarium w i l t observed by them are as

f o l l o w s : Meloidogyne hapla & Fusar i urn oxysporum f . spp .

7 1

vasinfectum 95, M. Javanica & F. oxysporum f. sp. vasinfectum

60, M. incognita & F. oxysporum f. sp. vasinfectum 60, Af.

incognita & F. oxysporum f. sp. vasinfectum 50, Af. arenaria &

F. oxysporum f. sp. vasinfectum 50, W. incognita acrita and

F. oxysporum f. sp. vasinfectum 15, Meloidogyne spp. alone

and check 0, percentage of dead plants in the above

treatments was 40, 5, 10, 4, 0, 3, 0 respectively. Kumar et

a7. (1988) observed that inoculation of either of M.

incognita or F. oxysporum f. sp. ciceris reduced growth of

chick-pea and highest reduction were obtained v»'nth

simultaneous inoculation of both pathogens followed by the

treatment in which the nematode inoculation preceded the

fungus by 10 days. Multiplication of nematodes and galling

was reduced in the presence of fungus. Mani and Sethi (1987)

studied the effect of the combined incoula of M. incognita,

Fusarium oxysporum or F. soTani on growth of chick-pea which

was found to be additive in nature. However, when nematode

was established earlier than the two fungi, the resultant

effect was more than simple additive. All the three organisms

affected the rhizobial nodulation considerably. Occurrence

of M. incognita in combination with F. oxysporum f.sp.

ciceris and F. solani, not only increased the severity of

disease but also shortened the incubation period for disease

expression. F. oxysporum f. sp. ciceris did not affect the

nematode population significantly. Patel et a7. (1987) also

observed increase in incidence of chick-pea wilt due to F.

7 2

oxysporum f. s p . ciceris i n p resence o f M. incognita.

Simultaneous i nocu la t i on of both pathogens resu l ted i n more

w i l t percentage. Mart in et al. (1956) s tudied i n t e r a c t i o n of

Fusarium oxysporum f . s p . vasinfectum causing w i l t o f co t ton

w i t h f i v e nematodes v i z . , M. incognita, M. incognita acrita,

Trichodours s p . , TyTenchorhynchus sp. and Helicotylenchus sp.

Of these nematodes, only M. incognita and M. incognita acrita

s i g n i f i c a n t l y increased incidence of w i l t i n the both w i l t

suscep t ib le and w i l t r e s i s t a n t v a r i e t i e s . The e f f e c t of M.

incognita Race 3 and F. oxysporum f . sp. vasr-^ectum on i-- -c

expression of co t ton was s tud ied by Ibrahim et al. (1982).

They o b s e r v e d t h a t p r e s e n c e o f nematode enhanced t h e

development and seve r i t y of w i l t . Expression of w i l t symptoms

was observed 10 days e a r l i e r i n the case of i n f e c t i o n w i t h

both organisms than w i th the fungus alone and reduc t ion in

p lan t growth were almost more than two- fo lds when the two

pathogens were present toge ther . Palmer and MacDonald (1974)

s tud ied maize roo t -kno t complex caused by Fusarium spp. i n

the presence o f va r i ous p l a n t p a r a s i t i c nematode s p e c i e s

i n c l u d i n g M. i ncogni ta, Pratylenchus penetrans, P.

herincissus, P. scribneri, P. nanus and Tylenchorhynchus

martini. Average dry root and shoot weight of maize seed l ing

i n o c u l a t e d w i t h M. incognita and F. mani 1 iforme were l e s s

than those of seed l i ng i n o c u l a t e d w i t h e i t h e r o rgan i sms

a lone. Goel and Gupta (1984) studied i n t e r a c t i o n between M.

Javanica and F. oxysporum f. sp. cieris. They f ound t h a t

7 3

shoot length was minimum when the fungus was inoculated a

week after nematode inoculation, whereas root length, fresh

shoot and root weights were significantly less when fungus

were inoculated a week before nematode inoculation. After

two years in the same field of study they observed maximum

and significant reduction in shoot length and fresh weight

when both the pathogens were inoculated simultaneously. A

maximum and significant reduction in number of galls was

recorded when nematode and fungus were present together, " he

reduction in the presence of F. oxysporum f. sp. cicerit wat

attributed either to poor and delayed nematode development or

to inhibitory effect of fungus on hatching of egg masses

(Goel and Gupta, 1986). In pot experiments, Upadhyay and

Dwivedi (1987) observed that wilt symptoms were greatest in

chick-pea plants inoculated simultaneously with both M.

javanica and F. oxysporum f. sp. ciceris, followed by

severity by inoculations of the nematode preceding the fungus

and the fungus preceding the nematode. The maximum number of

root galls was recorded on roots inoculated with the nematode

alone and the minimum number on roots where inoculation of

the fungus preceded that of the nematode. The maximum

reduction in shoot weight occurred where inoculation of the

nematode preceded that of the fungus.

Padila et al., (1980) observed that Meloidogyne spp.

alone caused severe stunting, F. oxysporum alone caused no

detrimental effect, whereas concomitant inoculation of the

7-4-

nematode and fungus at planting caused the death of the

plants after 45 days.

Fungi non-pathogenic to a host plant may become

pathogenic in presence of nematodes. F. oxysporum f. sp.

lycopersici was not pathogenic to cucumber plant, but wilt

symptoms developed when M. incognita was in association of

fungus, but F. oxysporum f. sp. cucumerinum did not produce

symptom on tomato plants even when M. incognita was present

(Pelez et al., 1983). Smits and Noguera (1982) observed that

F. oxysporum f. sp. melon is and F. oxysporum f. sp.

lycopersici were pathogenic to only those eggplant seedings

that were infected with M. incognita. Lopes and Lordello

(1979) studied the wilt of Piper nigrum and observed that

more damage was done, when M. incognita and F. sol ani f. sp.

piperi were present together.

Nogurea and Smits (1982) suggested that root exudates

of tomatoes infected with M. incognita stimulate soil

microflora reproduction and account for the greater number of

colonies (per gram soil) of bacteria and fungi in infected

than in healthy plant. This increase, lowered the number of

actinomycetes antagonistic to F. oxysporum f. sp. lycopersici

and enhanced its pathogenic effect. Nogurea (1980) observed

that germination and growth of F. oxysporum f. sp.

lycopersici in root extracts of a Fusarium resistant tomato

was significantly greater when tomatoes had been infected

T 5

wi th M. incognita. A f te r four weeks of nematode i n f e c t i o n ,

the amount of amino acids in the roots had increased by 509

and ca rbohydra tes by 112% and t h i s was assumed t o be t h e

reason f o r the breaking of res is tance to Fusarium. I n f l uence

of M. incognita on the l o c a l i z a t i o n of F. oxysporum f . sp.

lycopersici i n tomato was s t u d i e d by Noguera ( 1 9 8 3 ) . He

observed t h a t funga l p e n e t r a t i o n was no t r e s t r i c t e d t o

nematode s i t e but occur red t h r o u g h o u t t he r o o t c o r t e x and

advanced i n t o t h e stem v i a t h e x y l e m . Nematode a', ". - c -

appeared t o cause systemic change i n t h e p l a n t t i s s u e .

Mon ta l ro and Melendez (1986) s t u d i e d h i s t o p a t h o l o g y o f

i n t e r a c t i o n between F. oxysporum f . sp. dioscoreae and two

nematode species on yam. Examination of roo t t i s s u e s showed

t h a t fungal c o l o n i z a t i o n occurred i n d i s c r i m i n a t e l y , e i t h e r

i n t e r - o r i n t r a c e l l u l a r l y . C o l o n i z a t i o n i n t h e stem was

r e s t r i c t e d t o t h e v a s c u l a r s y s t e m , w i t h a b u n d a n t

p r o l i f e r a t i o n o f hyphae, ma in l y i n t he noda l t i s s u e s .

Apparent ly M. incognita and the fungus co lon ized i n d i f f e r e n t

sec tors of the invaded t i s s u e s , though abundant and v igour

hyphae were p resen t in t i s s u e s m o d i f i e d by M. incognita,

i n d i c a t i n g a p o s i t i v e i n t e r a c t i o n . Pratylenchus coffeae was

sometimes observed wi th the fungus w i t h i n the same t i s s u e s ,

but t h i s assoc ia t i on had no e f f e c t on s e v e r i t y or inc idence

o f w i l t . K le ineke -Borche rs and Wyss (1982) o b s e r v e d t h a t

mixed i n f e c t i o n o f M. incognita and F. oxysporum f . s p .

lycopersici on tomato p l a n t s r e s u l t e d i n an i n c r e a s e i n

y 6

indole-acetic acid which may be responsible for quicker

appearance of typical wilt symptoms. Nogurea (1982) observed

that purified extracts of tomato roots infected with M.

incognita did not show rishitin, an anti-fungal substance

normally present in healthy plants. Nematode free plants also

showed the formation of several well developed tyose in the

xylem vessels of stem whereas in infected plants these were

absent or very reduced. They suggested that the loss o"*"

resistance of this tomato variety '.'~ '". oxysporum ^. c.

lycopersici infection was associated with the nematode

infection which interfered with rishitin and tyose

production. Morrell and Bloom (1981) studied effect of

temperature on expression of wilt symptom on tomato plants

inoculated with M. incognita and F. oxysporum f. sp.

lycopersici and observed that wilt severity was increased at

21°C but not at 16°C. Hillocks (1986) studied localised

effect of nematode on initial infection and a systemic effect

on subsequent disease development of plants. To achieve this,

cotton seedlings were grown with a divided root system and

inoculated with root-knot nematode, M. incognita and F.

oxysporum f. sp. vasinfectum on the same or opposite halves

of the root system. Wilt indices were increased by the

nematode, but only in plants where both organisms were

together on the same parts of the root system. However, in a

second experiments in which plants growing in Meloidogyne

infected soil were stem inoculated with the wilt pathogen.

7 7

the nematode caused an increase in w i l t s e v e r i t y , despite the

phys ica l separat ion of the two organisms.

Root -kno t nematodes are found a s s o c i a t e d w i t h o t h e r

w i l t causing fung i a l so . Shoemaker and Barker (1979) in a

m i c r o p l o t exper iment observed t h a t M. incognita had no

s i g n i f i c a n t e f f e c t on Vertici11ium dahaliae w i l t of tomato.

Goswami e t al. (1970) r e p o r t e d h i g h degree o f synerg ism

between M. incognita and Sclerotium rolfsii in b r i n j a l when

i n o c u l a t e d t o g e t h e r . P rasad et al. ( 1980 ) s t s j o i ec '-he

a s s o c i a t i o n o f Corticium rolfsii and M. incognita i n w i l t

complex of Solanum khasianum, a medicinal p l a n t . They found

t h a t 42% o f the p l a n t s w i l t e d , where t he fungus and t h e

nematodes were combined, but 12.5X w i l t e d w i t h t h e fungus

alone and no w i l t occurred w i th the nematode a lone. Venkata

Rao e t al. (1973) reported an assoc ia t ion of M. incognita

var . acrita on Phytophthora parasitica var . nicotianae on

p i p e r - b e t e l r oo t s , Azam et al. (1977) observed t h a t presence

o f M. incognita cons ide rab l y i n c r e a s e s t he i n c i dence o f

d isease caused by Rhi zoctoni a sol an i, Py^

Col letotrichum atrametarium, on eggplant , wj^c A<fi<M<fS

Synergism and antagonism have been oJj&feVved betij/r^'e^y

f ung i and o the r e n d o p a r a s i t i c nematodes t han r o o t - k n o t

nematodes. Jorgenson (1970) observed tha t i n t e r a c t i o n between

Heterodera schachtii and Fusarium oxysporum was

d isadvantageous t o the nematode and damage t o suge rbee t

. ^

7 3

plants were less when the fungus and nematodes were present

than when only the nematode was present. Edward and Singh

(1979), while studying the interaction between Heterodera

cajani and F. udum on pigeon-pea, found that the nematode

alone caused less damage to var. Type-21 than when

associated with F. udum. Hasan (1984) observed synergism

between H. cajani and F. udum attacking Cajanus cajan. He

found a significant increase in wilting when H. cajani and

F. udum were associated with pigeon-pea. Seinhorst and

Kuniyasu (1971) reported that rate of multiplication of

Rotylenchulus reniformis on pea var. "Rando" was increased by

the presence of F. oxysporum f. pisi race-1. Krishnaprasad

and Padanganur (1980) observed that soil from Verticillium

wilt affected plant harboured more Rotylenchulus reniformis

population compared to that of healthy plants. They concluded

that R. reniformis might be associated with Vertici 11 ium v^^^t

of cotton as evidenced by fairly high population of nematodes

in the rhizosphere and roots of diseased plants. Mountain and

Mckeen (1962), while studying the interaction of lesion

nematode, Pratylenchus penetrans with Verticil 1 ium dahliae on

tomato, observed that reproduction of nematode was enhanced

in such an interaction. In Vertici num-vl^\^X, of potato, the

damage were more when lesion nematode was present (Morsink

and Rich, 1968). Burpee and Bloom (1974) observed that

incubation period of V. albo-atrum was decreased in the

presence of P. penetrans. In another report, they showed that

7 9

Praty lenchus penetrans i n r o o t s o r r h i z o s p h e r e were

suppressed i n the presence of Vertici11ium (Burpee and Bloom,

1 9 7 8 ) . F e r r a z and Lear ( 1 9 7 6 ) f o u n d a s y n g e r g i s t i c

i n t e r a c t i o n between F. oxysporum f . sp. dianthi and nematodes

such as Criconemoides curvatum, Pratylenchus dianthus and M.

hapla on c a r n a t i o n . G r u j i c i c e t a1. (1984) examined the

lucerne f i e l d and repor ted t ha t damage due to w i l t and r o t

was g r e a t e r when P. penetrans and F. oxysporum v a r ,

medicaginis were p resen t t o g e t h e r , R iede l e t a 7. ( ^ " ^ f ,

r e p o r t e d a d i f f e r e n t i a l i n t e r a c t i o n s o f Praty1enchus

crenatus, P. penetrans and P. scribneri w i th V. dahliae i n

p o t a t o e a r l y dy ing d i sease . S t i n g nematode, Belonolaimus

longicaudatus have been found t o i n f l u e n c e i n c i d e n c e o f

co t ton w i l t caused by F. oxysporum f . sp. vasinfectum (Cooper

and Brod ie , 1963).

R o o t - k n o t nematodes have been f o u n d t o b reak t h e

res is tance of the crop p lan ts against so i l -bo rne pathogens.

Car ter (1978) repor ted enhancement of w i l t sever i t y in the

completely (po l ygen ic ) r e s i s t a n t c u l t i v a r s of tomato as a

r e s u l t of M. incognita and F. oxysporum f . sp. lycopersici

i n t e r a c t i o n . Hadiastono (1981) observed tha t tomato v a r i e t i e s

o r i g i n a l l y r e s i s t a n t to F. oxysporum became suscept ib le when

inocu la ted w i t h Meloidogyne spp. Harr ison and Young (1941)

observed t h a t r o o t - k n o t nematodes reduced the w i l t res is tance

of many v a r i e t i e s of tomatoes. In a glasshouse experiment 20

eo

tomato l i n e s and v a r i e t i e s inocu la ted w i t h a Fusarium p lus

Meloidogyne were found t o be s u s c e p t i b l e i n c l u d i n g those

r e s i s t a n t t o F. oxysporum f. sp . lycopersici. Donald and

Johnson (1973) inocu la ted e igh t c u l t i v a r s of watermelon w i th

known r e a c t i o n s t o Fusarium w i l t w i t h M. incognita and

observed t h a t w i l t symptoms were increased more in r e s i s t a n t

than in suscep t ib le c u l t i v a r s , Johnson and L i t t r e l l (1969)

observed t h a t M. incognita, M. hapla and M. Javanica d id not

break r e s i s t a n c e o f chrysanthemum aga" ">- t F. .--r^^por ••<•.

O'Ereo le et al. (1982) i n an i n v e s t i g a t i o n - r .vo ' .v-ng f o u r

v a r i e t i e s of tomato showing res is tance t o M. incognita and

one not res is tance showed tha t i n f e c t i o n w i t h F. oxysporum f .

sp . lycopersici was g rea te r i n t he nematode s u s c e p t i b l e

v a r i e t y than in o ther more r e s i s t a n t v a r i e t i e s . They observed

s i m i l a r (a l though less conc lus ive) r e s u l t s w i t h Vertici11ium

dahliae. Kle ineke-Borchers and Wyss (1982) noted t h a t p r i o r

i n f e c t i o n o f M. incognita f o l l o w e d by Fusarium oxysporum

i nocu la t i on g r e a t l y enhanced fungal disease in both Fusarium

suscep t ib le and r e s i s t a n t tomato p l a n t s . P i tcher (1974) a lso

proved t h a t i n f e c t i o n of "Pearson VF" tomato wh ich i s

moderate ly r e s i s t a n t t o F. oxysporum f . sp . 1 ycopersici

became suscep t ib le t o t h i s fungus in presence of M. javanica.

Thomason (1958) found tha t w i l t in Vigna sinensis was more

s e v e r e i n p l a n t s grown i n s o i l i n f e s t e d w i t h b o t h F.

oxysporum f . sp. tracheifilum and M. Javanica than in s o i l

i n fes ted w i th fungus alone. McGuire e t al. (1958) observed

a 1

tha t on ly )0% p lan ts showed the w i l t symptoms when i n fec ted

w i th M. incognita acrita and 15% w i th F. oxysporum f. sp.

vasinfectum a lone , whereas 95%, 60% and 50% p lan ts became

w i l t e d when the fungus was present in combination w i t h M.

hap7a, M. Javanica and M. incognita r espec t i ve l y .

D a v i s and J e n k i n s ( 1963 ) o b s e r v e d a s y n e r g i s t i c

response between Meloidogyne spp. and Fusariun^-vi^'St r e s i s t a n t

pea v a r i e t y . An increase i n s e v e r i t y o f Fasar7u/n-wi 11 o f

tomato and increased co lon i za t i on o^ fungus in the vascular

t i ssue were observed when M. incognita was present (Car ter

et al. y 1977). Garber et al., (1979) found t h a t i n s o i l

i n f e s t e d w i t h F. oxysporum f . s p . vasinfectum and M.

incognita, the ex tent of fungal invasion and c o l o n i z a t i o n of

c o t t o n was c o r r e l a t e d w i t h the nematode g a l l i n g . Noguera

(1983) observed t h a t r o o t s o f tomato p l a n t s o n l y showed

c o l o n i z a t i o n by F. oxysporum when in fec ted w i th M. incognita.

b. I n t e r a c t i o n w i t h r o o t - r o t fung i

Many i n v e s t i g a t o r s have not iced t ha t nematodes i n t e r a c t

w i t h r o o t - r o t fung i s y n e r g i s t i c a l l y , hence greater damage t o

p l a n t . Tu and Cheng (1971) found t ha t s e v e r i t y of r o o t - r o o t

i n k e n a f (Hibiscus cannabinus L . ) was i n c r e a s e d when

seed l i ngs were i n f e c t e d s i m u l t a n e o u s l y by Macrophomi na

phased ina and M. javanica. Mishra et al. (1988) observed

tha t M. incognita provided a good s i t e f o r easy en t ry of the

developing hyphae of R. bataticola {M. phased ina) in whi te

3 2

jute {Corchorus capsularis) and thus increased the severity

of the disease. The number of dead plants were increased

significantly when pathogens were inoculated together. Goel

and Gupta (1986) observed that irrespective of time, combined

inoculation of M. Javanica and R. bataticola on chick-pea

reduced growth parameters compared with when inoculated

alone. The number of root galls was significantly reduced

when nematode was inoculated 7 days before the fungus. Bruton

and Heald (1987) studied effect of M. phaseol i na on

cantaloupe in the presence of M. incogni ta and found

reduction in top dry weight of the plant. Apt and Koike

(1962) studied the relationship of M. incognita acrita with

Pythium graminicola on sugarcane. Colin and Powell (1971)

reported an extensive fungal colonization in the root-rot

susceptible cultivar of tomato "Dixie Bright 101" when M.

incognita preceded R. solani by 21 days. Sharma et a 7.

(1980) reported a syngergistic effect on the root-rotting of

okra plants when M. incognita and R. bataticola were

combined together. Al-Hazmi (1985) reported that severity of

root-rot caused by M. phaseolina in root-rot disease complex

of French bean {Phaseolus vulgaris) increased when the

nematode was introduced 2 weeks before the fungus, and if the

fungus was introduced first, then the nematode infection and

reproduction were reduced. Chhabra and Sharma (1981) in a pot

trial with okra and eggplant observed that M. incognita and

R. bataticola significantly reduced the germination of both

8 3

TABLE 10

Interaction of root-knot neiatodes vith Hilt causing Fusaria and root-rot fungi.

Heloidogyne spp. Associated organisi Host Coitents References

H. incognita

H. incognita

H. incognita

H. incognita

H. incognita

H. incognita

H. incognita

H. incognita

H. incognita

Fusariut equiseti

F. oxysporua f. sp. nicotianae

F. oxysporut f. sp. ciceris

F. solani

F. oxysporut f.sp. telonis F. oxysporut f.sp. lycopersici

Fusariut spp.

Fusariut toniliforte

F. oxysporut f.sp. lycopersici

F. oxysporut f.sp. lycopersici

Pea Preponded wilt syiptoi Chahal and Chhabra, appearance 1985

Tobacco Significant infection Porter and PoNell, occurred only when both 1967 pathogens Mere present

Chickpea Increased tiilt severity Hani and Sethi, 1987; and shortened incubation Patel et al.. 1987; period of disease Ki'nar ?: a!., :98f expression

Chickpea Increased Milt severity Hani & Sethi, 1987 and shortened incubation period of disease expression

Bringal Non-pathogenic fungi Stits i Noguera, caused severe vascular 1982 necrosis of the shoots

Hatertelon Increased Nilt severity Donald i Johnson, 1973

Haize Increased root-rot severity

CucuBber Non-pathogenic fungus caused wilting in presence of nenatode

Palier & HacDonald, 1974

Pelez et al., 1983

Toiato Increased Hilt severity Horrell and Blooi, 1981; Kleineke-Borehers and «yss, 1982; Carter et al., 1977.

Table 10 contd..

a^

Heloidogyne spp. Associated organist Host Coiients References

h. incognita

H. incognita

M. incognita

h. incognita

M. incognita

M. incognita

F. oxysporua f.sp. vasinfectua

F. oxysporua f.sp. pisi

F. oxysporua f.sp. vasinfectua

R. bataticola

/?. solani

R. solani

Cotton Increased wilt severity Cooper & Brodie, 1963; Martin et a l . , 1956; Ibrahii et a l . , 1982; Hillocks, 1986

Pea Increased wilt severity Padilla et a l . , 1980

Alfalfa Increased wilt severity McGuire et a l . , 1958

French Increased severity o* ^l-Hazmi, 1985 bean root-rot

Cotton Synergist occurred

Tobacco Worst infection occurred when netatode inoculated 10 or 21 days before fungi

Carter, 1975

Batten and Powell, 1971

M.

n.

M.

H.

H.

n.

H.

incognita

incognita

incognita

incognita

incognita

incognita

incognita acrita

R.

R.

H.

R.

R.

R.

F.

solani

solani

phaseolina

solani

solani

bataticola

Potato

Okra

Hhite jute

Toaato

French bean

Okra

oxysporua f.sp. pisi Pea

Increased disease severity

Sharna and Gill, 1979

Siiultaneous inoculation Chhabra et ai.,1977 caused Hax reduction

Increased disease severity

Increased fungal colo­nization

Increased disease severity

Increased root-rot

Synergistic response observed, broke resistance

Mishra et al., 1988

Colin and Powell, 1971

Reddy et ai.,1979

Sharea et al., 1980

Davis and Jenkins, 1963

Table 10 contd..

es

Meloidogyne spp. Associated organist Host Conents References

M. incognita acrita R. solani

h. incognita acrita F. oxysporut f.sp. cubense

h. incognita

H. javanica

H. javanica

M. javanica

H. javanica

H. javanica

H. javanica

H. javanica

H. javanica

H. javanica

R. solani

F. oxysporut f.sp. ciceris

F. oxysporut f.sp. tracheiphilut

F. oxysporut f.sp. telonis

F. oxysporut f.sp. lycopersici

F. oxysporut

F. udut

R. bataticola

R. bataticola

R. solani

Cotton Disease increased Reynolds and Hanson, 1957

Banana Incubation period of Loos, 1959 fungus shortened

Toaato Reduction in growth Chahal and Chhabra, paraneters 1984

Chickpea Significant reduction Upadhyay and Kusui in groMth paraieters DHivedi, 1987;

Chhabra et ai..l977; Goel a!\C GuDta. 1984 l%t

CoMpea Increased Nilt severity Thonason et ai.,1959

Huskielon Increased wilt severity, broke resistance

Totato Susceptibility to Milt increased

Chrysan- Early and severe Milt theaui appearance

Pigeon- Susceptibility to Milt pea increased

Chickpea Reduced growth paraieters

To«ato Increased nil ting incidence

CoMpea Plant growth reduced when neaatode inoculation was done 3 weeks prior to the fungus

Orion and Hetzer, 1981

Jenkins and Coursen, 1957; Bergeson et a l . , 1970

Johnsot) and Littrell, 1%9

Abdul Salai and Xhan, 1986

Goel and Gupta, 1986

Goswa«i et al., 1976

Kunar et a l . , 1988

Table 10 contd..

a©

Heloidogyne spp. Associated organisB Host Coiients References

«.

M.

H.

tt.

H.

H.

H.

He

javanica

javanica

hapla

hapla

hapla

arenaria

arenaria

loidogyne spp.

H. phaseolina

R. bataticola

F. oxysporuB f.sp lycopersici

F. oxysporut f.sp vasinfectuB

F. oxysporuB

F. oxysporva f.sp nicotianae

F. solani

F. oxysporua f.sp lycopersici

Kenaf Increased severity of Tu and Cheng, 1971 root-rot

French Reduced gronth para- Reddy et al., 1979 bean leters

Tonato Hilt incidence increased Jenkins and Coursen, 1957

ftlfalfa Severe wilting appeared HcGuire et aJ.,1958

Chrysan- Hilt incidence increasec Johnson ana Liitrel thenun 1969

Tobacco Significant infection Porter and Powell, occurred only Nhen both 1967 pathogens present

Ground Earlier appearance of Patel et al., 1985 nut Milt syiptons

Tonato Resistance broken Aliedia, 1972

Heloidogyne spp. F. oxysporua Toiato Resistance broken Nadiastono, 1981

3 T

spec ies when they were p resent t o g e t h e r i n t h e s u b s t r a t e .

Goswami e t al. (1976) noted t h a t when M. javanica was

inocu la ted onto tomato p l a n t s , 3-weeks before i n f e c t i o n w i t h

R. bataticola, 33.3X w i l t i n g occur red. Approximately 13.3,

6.7 and 6.7% w i l l e y was noted a f t e r simultaneous pathogen

i n o c u l a t i o n ; fungus i n f e c t i o n alone or fungus i n f e c t i o n 3-

weeks before nematode i n o c u l a t i o n s , r e s p e c t i v e l y . Sakhuja

and Sethi (1986) observed t ha t m u l t i p l i c a t i o n of M. Javanica

and the g a l l i n g on groundnut was adversely af-Pet et b:

bataticola and F. solani. Reduction in m u l t i p l i c a t i o n was

maximum wherever one or both t h e f u n g i were i n o c u l a t e d

s imul taneously w i t h the nematode, but R. bataticola proved t o

be more an tagon i s t i c to M. javanica.

Khan and Mul le r (1982) s tud ied the i n t e r a c t i o n between

R. solani and M. hapla on r a d i s h {Raphanus sativus) i n

g n o t o b i o t i c c u l t u r e in p e t r i d i s h e s . This experiment i nd i ca ted

t h a t the phys io log i ca l changes in the ga l l ed reg ion due to

nematode i n f e c t i o n predisposed the roots f o r invas ion and

r a p i d c o l o n i z a t i o n by the f u n g u s . Reddy e t al. (1979)

repor ted t ha t roo t -kno t nematode, M. incognita and R. solani

are o f t e n found assoc ia ted s i m u l t a n e o u s l y w i t h r o o t s o f

f r e n c h bean (Phaseolus vulgaris) under f i e l d c o n d i t i o n s .

Reduct ion in growth parameters were observed when bo th

pathogens were present at a t i m e . Kanwar e t al. (1988)

observed t h a t growth of cowpea was s i g n i f i c a n t l y reduced

when M. javanica was inoculated 3 weeks p r i o r to R. solani.

The number o f b a c t e r i a l n o d u l e s and g a l l s was r e d u c e d

s i g n i f i c a n t l y i n presence of bo th pathogen w i t h maximum

reduc t ion in nematode alone t reatment . Sharma and G i l l (1979)

observed s i g n i f i c a n t r e d u c t i o n i n shoo t w e i g h t o f p o t a t o

p l a n t inocu la ted w i t h M. incognita and / or R. solani and

maximum r e d u c t i o n i n m u l t i p l i c a t i o n o f nematode (66.725K)

occurred when R. solani was inoculated before M. incognita.

Chahal and Chhabra (1984a) reported t h a t M. incognita and R.

solani separate ly as wel l as in combination s i g n i f i c a n t l y

reduced shoot l eng th , shoot and root weights of tomato. They

f u r t h e r observed t h a t i nocu la t i on of tomato seedl ings w i t h M.

incognita and R. solani reduced seed g e r m i n a t i o n t o 18%

compared w i th 48% and 39% in the case of s i ng l e i n o c u l a t i o n

o f M. incognita and R. solani r e s p e c t i v e l y (Chahal and

Chhabra 1 9 8 4 b ) . Chhabra et al. ( 1 9 7 7 ) showed t h a t

i n t e r a c t i o n i n v o l v i n g R. solani and M. incognita on o k r a

s i g n i f i c a n t l y reduced shoot and root lengths and wet and dry

w e i g h t s . H a z a r i k a and Roy ( 1 9 7 5 ) examined t h e

i n t e r r e l a t i o n s h i p between R. solani and M. incognita on

eggplant and found t h a t number of g a l l s and egg masses on

roo ts were s i g n i f i c a n t l y greater in p lan ts inocu la ted w i th

nematode and fungus together than in those inocu la ted w i th

nematode alone. Chhabra et al (1977) observed t h a t maximum

reduc t i on in growth parameters of okra was obtained when M.

incognita and R. solani were i n o c u l a t e d s i m u l t a n e o u s l y .

8 9

Fungus with mechanical injury of roots was more damaging to

plants than the fungus alone, Chhabra et a1. (1978) studied

the influence of soil types on the interaction of R. solani

and M. incognita and found that inoculation of okra with

both the pathogens markedly reduced shoot and root growth.

Nematode population were much denser in sandy loam as compare

to loamy sand or sandy clay loam, but number of galls did not

vary between soil types.

Powell et al. (1971) noticed that soi1-bo»-ne " mg- l--c

Pythium, Curvularia and Botrytis caused extensive root decay

when root-knot nematode preceded the fungi. M. incognita was

found associated in a root-rot with F. concoTar in papaw and

with F. oxysporum in tomato (Saeed et a7, 1972). M. arenaria

appeared to predispose the maize plant to S. rolfsii (Minton

et al., 1975). Welty et al. (1980) found that Phytophthora

megasperma f. sp. medicaginis intensified root-rot severity

in resistant and susceptible lucerne when M. hapla or M.

incognita were present. Mukhtar and Khan (1989) observed

greatest suppression in chick-pea plant when they were

inoculated simultaneously with M. Javanica and S. {Corticium)

rolfsii, followed by the fungus prior to nematode.

Besides root-knot, other nematodes also have been

found to interact with root-rot fungi, Kisiel et al. (1969)

studied the possible interactions between nematodes,

Tylenchus agricola and Tylenchorhynchus claytoni on root-rot

9 0

of corn caused by F, roseum and pythiurn ultimum. Nematode

population increased to a greater degree in plants inoculated

with F. roseum than with P. uTtimum. Penetration of stele of

F. roseum was significantly greater in presence of nematodes.

They concluded that nematode may in some cases increase the

severity of the disease, but the fungus was by so far the

dominant pathogen in this relationship. Littrell and Johnson

(1969) observed an interaction in combined inoculation with

Pythiurn aphanidermatum and BeTonolaimus longicaudatus on

chrysanthemum. Sobun et al. (1979) reported an

interrelationship between Tylenchorhynchus and root-rot

fungus on chick-pea. Upadhyay and Swarup (1981) observed a

significant reduction in growth of maize plant, when both

Tylenchorhynchus vulgaris and F. moniliforme were inoculated

together. Abawi et al. (1985) studied the disease complex of

Phased us vulgaris caused by one or more species of Fusarium,

Rhizoctonia, and Thielaviopsis with lesion nematode,

Pratylenchus spp. Studies on interactions of Vertici11ium

dahliae, Colletotrichum coccodes, Rhi zoctoni a solani and

Pratylenchus penetrans in the early dying syndrome of potato

revealed an additive symptom expression, when P. penetrans

combined with V. dahliae (Kotcon et al., 1985).

Interaction of nematode and fungal plant pathogens under

pollutant stress

Apparently no attempt has been made to determine the

impact of air pollution stress on fungus-nematode interaction

9 1

in disease complexes. Effects of some heavy metals as soil

pollutants have been studied by some workers in nematode-

fungus complexes. Khan and Abul Salam (1990) studied effects

of nickel (Ni) and cobalt (Co) at different concentrations oh

interaction of Meloidogyne Javanica, Fusariurn udum and

Rhizobium on pigeonpea. They observed that M. javanica and F.

udum interacted synergistical 1 y and caused more severe

wilting symptoms than F. udum, but the result was reverse in

the presence of Ni, i.e. wilting was completely in-''--'tet -

root galling was suppressed but it caused reduction in plant

growth and nodulation. They suggested that this may be due to

toxic effect of nickel towards the pathogens. It was found

that cobalt too, suppressed the wilting symptoms on the test

plants by F. udum, and had similar effect as a nickel. Cobalt

increased galling produced by M. javanica and caused a

significant reduction in growth parameters of the plant.

The review of literature shows that in recent years

some studies have been conducted on interactions between

biotic pathogens (including fungi and nematodes) and some

gaseous air pollutants. The ability of some biotic pathogens,

particularly viruses, bacteria and fungi to influence the

susceptibility of the plants to air pollutants has been

Whether the nematodes also influence the plant susceptibility

to air pollutants is yet to be explored fully. The effect of

gaseous air pollutants on the interactions between nematodes

9 2

and fungi has not gained study. Whether the disease i n t e n s i t y

caused by nematodes or f u n g i o r t h e d i s e a s e s e v e r i t y

developing through t h e i r i n t e r a c t i v e e f f e c t in a s y n e r g i s t i c

r e l a t i o n s h i p are i n f l u e n c e d a d v e r s e l y or f a v o u r a b l y or

whether t h i s r e l a t i o n s h i p i s i m p a i r e d on a i r p o l l u t i o n

stressed needs t o be examined. The present study i s planned

to answer some of these quest ions.

MATERIAL AND METHODS

The method t o be employed and steps to be taken f o r

o b t a i n i n g t h e m a t e r i a l s f o r c o n d u c t i n g t h e p roposed

i n v e s t i g a t i o n s w i l l be as f o l l o w s :

1 . Root-knot nematode population

a. Collection of field populations:

F i e l d p l o t s grown w i t h v e g e t a b l e s and pu l ses i n and

around A l i g a r h w i l l be surveyed t o c o l l e c t r o o t samples

i n fec ted w i t h roo t - kno t nematodes. Root samples co l l e c ted in

polythene bags and proper ly marked w i l l be brought t o the

l abo ra to ry for species i d e n t i f i c a t i o n and es tab l i sh i ng of

s i n g l e egg mass popu la t i on .

b. I d e n t i f i c a t i o n of species

The species of roo t - kno t nematodes present in the root

samp les w i l l be i d e n t i f i e d by u s i n g p e r i n e a l p a t t e r n

c h a r a c t e r i s t i c s of mature females (Eisenback et al. , 1981)

and by conduct ing North Caro l ina host d i f f e r e n t i a t e t e s t s

(Tay lor and Sasser, 1978).

( i ) Perineal pattern method

For t h e i d e n t i f i c a t i o n o f s p e c i e s o f Meloidogyne

present in roo t samples, mature females w i l l be d issected out

f rom the g a l l s o f the roo t samples . P e r i n e a l p a t t e r n s o f

f e m a l e s ( 1 0 - 2 0 ) f r o m each sample w i l l be p r e p a r e d and

examined under microscope to study t h e i r c h a r a c t e r i s t i c s . The

species will be identified on the basis of perineal pattern

characteristics (Eisenback et a/., 1981).

(ii) North Carolina host differential test:

The species of Meloidogyne present in the root samples

will be maintained on tomato (cv. Pusa Ruby) or eggplant

(cv. Pusa Kranti ) in pots. Chopped roots from the samples

will be added to pots filled with steamed sterilized field

soil. Tomato or egg plant seedlings will be planted in the

pots. From these field populations, single egg nr, .se ou''. ur,j&

of the species of Meloidogyne will be raised on tomato or

eggplant grown in steam-sterilized soils in pots. For

conducting North Carolina host differential tests to

establish the identity of species, seedings of tomato cv.

Rutgers, tobacco, cv. NC95, pepper cv. California Wounder,

peanut cv. Florrunner, watermelon cv. Charlston Gery and

cotton cv. Delptapine 61 will be grown in clay pots

containing sterlized soils in pots in triplicate. Two

additional pots of tomato will be included to determine the

time of termination of test. Plants will be inoculated with

5,000 freshly hatched second stage juveniles (J2) per pots in

the vicinity of roots of test plants and pots will be kept

at glasshouse benches (temp. 27-30°C). The roots will be

harvested 50-60 days after inoculation and will be washed

thoroughly with tap water and examined for the presence of

galls and egg masses. In case of very light infection, roots

9 5

will be stained with phloxine B to visiulize the minute egg

masses. Galls and egg masses will be counted and GI and EMI

will be rated on 0-5 scale (Taylor and Sasser, 1978).

After rating the root system, result will be compared

with the differential host teet reaction chart (Table 11) to

identify four species of Meloidogyne viz., M. incognita, M.

Javanica, M. arenaria and M. hapla. The results will also

differentiats races in M. incognita and M. arenaria. Results

will be compared with identification made earlier on the

basis of perineal pattern for confirmation of their identity.

c. Maintenance of inoculum

After identification of the species, single egg mass

cultures of the species of root-knot nematodes will be raised

on tomato or eggplant seedlings in greenhouse conditions by

inoculating 10-15 egg masses of single egg mass cultures used

in North Carolina host differential tests. Sub-culturing will

be done by inoculating new seedlings of tomato or eggplant

with at least 15 egg masses, each obtained from the single

egg mass culture in order to maintain sufficient inoculum for

further studies. The results of the host differential tests

will also differentiate races in M. incognita populations.

d. Inoculation

The plants in the proposed study will be inoculated in

the form of second stage juveniles (J2)- Second stage

juveniles will be obtained by incubating egg masses from the

9 e

cultures of nematode in sterilized water in petri dishes at

25°C. The number of juveniles (J2) in the suspension will be

standardized before inoculation of the seedlings in pots. The

described amount of suspension will be taken by micropippet

controller and added near the roots into 4-5 holes made

around the seedlings. The holes will be covered with the soil

after inoculation. The inoculum level (Pi) of 0,10,100,

1000,10000 and 2000 Jg per pot is planned to be used.

2. Inocula of Fusariurn oxysporum f. sp. cicerTs and

Rhizoctonia bataticoTa

Pure cultures of the two fungi, F. oxysporum f. sp.

ciceris (Padwick) Chattopad iyay and Sen Gupta pathogenic on

causing wilt on chickpea and R. batiticola (Taub.) Butl .

causing root-rot on soybean will be obtained from the

Division of Mycology or Plant Pathology, Indian Agricultural

Research Institute, New Delhi.

a. Maintenance and pure cultuning

The fungi will be sub-cultured and maintained on PDA

slants as stock cultures. The fungi will be sub-cultured on

fresh PDA slants at regular intervals.

b. Prepration of inoculum

In order t o ob ta in enough inocu la of the fungi f o r the

expe r imen ts , Czapek's l i q u i d medium w i t h the f o l l o w i n g

cons t i t uen t s w i l l be used as a c u l t u r e medium:

3 7

TABLE 11

North Carolina differential host test reaction chart

Heloidogyne Cotton cv. Tobacco cv. Pepper cv. Naterielon cv. Peanut cv. ToBato cv. species and races Deltapine 16 NC 95 California Charleston florrunner Rutgers

Honder Grey

H. incognita

Race 1

Race 2

Race 3

Race 4

-

-

t

+

-

+

-

t

M. J3vanic3 - +

H. arenaria

Race 1 - +

Race 2 - +

H. hap I a - +

• (0 (*)

B Q

Box indicates key differential host plant Parenthesis indicate that a siall proportion of the population attacks the host + : Susceptible; - : Resistant.

9 3

KNO3 2g

KHg PO4 1 g

Mg SO4 0.5 g

Kcl 0.5 g

Sucrose 30 g

Distilled water 1000 ml.

The prepared medium will be filtered through muslin

cloth. One hundred ml. of the medium will be transfered into

250 ml. flasks and the flasks will be properly plugged with

non-absorbent cotton. Sterilization of the flasks containing

the medium will be done in an autoclave at 15 lbs. presssure

for 15 minutes. With the help of sterilized inoculation

needle, the fungal mycelium will be transfered from the PDA

slants to the flaks at laminar flow bench. Inoculated flasks

will be incubated at 23-25°C for 7 days to allow mycelial

growth of the fungi. At the end of the inoculation period,

the content of the flaks will be poured over in a funnel

lined with Whatman filter paper N0.I. The mycelium mat

collected in the funnel will be washed with distilled water

to remove the traces of the medium and mycelial mat will be

gently pressed between the folds of sterile blotting paper

to remove the excess amount of water. Inoculum in form of

suspension will be prepared by blending 10 g fungal mycelium

in 100 ml. of sterilized distilled water for 30 seconds in a

9 3

Waring blender. Thus, each 10 ml. of this suspension will

contain about 1 g of the fungus,

3. Pollutant (Sulphur dioxide):

a. Exposure chamber

Experimental plants grown in pots for the treatments

receiving SO2 exposure intermittently will be exposed to

sulphur dioxide in air pollutant exposure chamber (Standard

Appliances, Varansi) which is equipped with a full size door,

and an exhaust duct at its top to carry out the .i'if.r -;fous

mixture. The chamber's bottom is double walled, upper side

has opening, and a blower is attached to the lower side.

Voltage supply to blower will be regulated by a voltage

controller which is displayed on a panel meter. The potted

plants which are to be treated will be kept in the exposure

chamber and will be exposed for a desirable length of time.

The concentration of the gas, though regulated by the voltage

supply, will be determined by sampling of the air in chamber

and analysis of the sampled air.

b. Generation of SOg Gas

By the action of sulphuric acid (H2 SO^) on sodium

sulphite (Na2 SO3), SOg gas will be produced in a generator

under contol reaction conditions. The amount of Na2 SO3 and

H2SO4 discharged from the reagent bottles mounted over the

SO2 generator will be determined by collecting the solution

dropping through capillary tube in a graduated cylinder for

1 O O

sometime and e x p r e s s i n g the r a t e i n m l /m i n on the bas i s o f

f l o w r a t e o r s o l u t i o n f e e d i n g r a t e . S o l u t i o n o f s o i d u m

s u l p h i t e (Na2 SOo) and s u l p h u r i c a c i d (10%) w i l l be p repa red ,

t o p r o d u c e r e q u i r e d amount o f SOg g a s / m i n . On c o m p l e t e

r e a c t i o n 1M NagSOg produces 1M. SOg or 126 mg NagSOg produces

64 mg SO2. 10% Hp SO^ s o l u t i o n w i l l be used f o r a l l t h e

w o r k i n g s o l u t i o n s o f Na2S02. The r e a c t i o n i s shown below:

Nag SO3 + HgSO^ > SOg+Nag SO^ + HgO

c . Exposure and doses

Exposure of the plants will be done intermittently.

Seedlings will be exposed to SOg when they are 3-4 weeks old

at alternate days for 3 h. for each exposure. This procedure

will be continued for 75 days. The concentrations of the SOg

proposed to be used for the exposure will be 0.1 and 0.2 ppm.

d. Air pollution symptoms

The experimental plants of chickpea and soybean treated

with SO2 will be regularly examined for SOg induced symptoms.

The symptoms if present will be noted and characterized.

e . Sampl ing

Sampl ing o f t h e a i r w i t h i n t he exposure chambers w i l l

be done by Handy A i r Sampler (K imo to , Japan) a t the r a t e o f

200 m l . a i r per m inu te f o r 3 m in . For sampl ing o f gaseous a i r

p o l l u t a n t s , m e t h o d s b e i n g f o l l o w e d a t t h e N a t i o n a l

1 O 1

Environmental Engineering Research Institute (NEERI), Nagpur,

(Anon, 1986) will be employed.

f. Analysis of sulphur dioxide

Analysis of sulphur dioxide in sample will be done by

Weast and Fack method (being used at NEERI). Some details of

the analysis, preparation of chemicals are described

stepwise, below:

(i) Absorbing reagent (Sodium tetrachloromercurate)

27.2 g meruric chloride and 11.7 g sodiun. en o n o e

will be dissolved in 1 lit. double distlled water (D.D.W.).

This solution will be stored at room temperature and can be

used for two months.

(ii) Sulphamic acid (0.6%)

0.6 g sulphamic acid will be dissolved in D.D.W. to

bring the volume to 100 ml.

(iii) Formaldehyde solution (0.2X, to be prepared fresh).

0.5 ml formaldehyde solution (40%) will be diluted in

D.D.W. to 100 ml.

(iv) Rosaniline hydrochloride solution (0.2%)

a. Step I solution

0.2 g rasaniline hydrochloride will be dissolved in 1 N

hydrochloric acid to bring the volume up to 100 ml. It will

be kept in refrigerator over night.

1 0 2

b. Step II solution

4 ml . of step I and 6 ml concentrated HCl will be

dissolved in D.D.W. to bring the volume to 100 ml.

(v) Potassium dichromate solution (0.1 N)

Exactly 1.226 g dried potassium dichromate will be

dissolved in D.D.W. to 250 ml.

(vi) Sodium thiosulphate (0.1 N)

7.0 g sodium thiosulphate will be disso ecf n 250

D.D.W. For preservation 2 ml. of chloroform will also oe

added.

(vii) Iodine solution (0.1 N)

10 g of potassium iodine will be dissolved in 20 ml

D.D.W. After adding 3 g crystals of iodine, solution will be

stirred. Solution will be kept over-night and dilluted up to

250 ml with D.D.W. Solution will be preserved in amber

coloured bottle in dark.

(viii) Potassium iodine solution (100%)

10 g of potassium iodine will be dissolved in 10 ml of

D.D.W, This may be prepared at the time of titration.

(ix) Starch solution

A paste of 1.25 g soluble starch will be prepared with

D.D.W. and will be poured in 250 ml boiling D.D.W. It will be

1 0 3

boiled for 5 minutes with stirring and allowed to cool on

stand. Fresh and clear supernatent will be used.

(x) Metabisulphite solution

0.3 g sodium metabisulphite will be dissolved in 500 ml

D.D.W. This solution will contain 320 or 400 ug/ml of SOg.

g. Standardisation of sodium thiosulphate

50 ml D.D.W. will be poured into a 250 ml conical flask

and add to it 10 ml of potassium dichromate (0. ' h; •'C

H2 SO. (1:1) and 1 ml of potassium iodine solution wii be

added to it. The flask will be kept in dark for 5 minutes for

reaction.

Above solution will be titrated with sodium thio­

sulphate (vi) till a faint yellow colour is obtained. Then 1

ml of starch solution will be added; blue colour will now

appear. The titration will be countinued until faint blue

colour disappears. Final colour will be distinct bluish green

tinge due to chromous ions. Titration reading will be noted.

This will be repeated to get constant reading. Then normality

of sodium thiosulphate will be calculated according to the

following formula.

Normality of dichromate x vol. of dichromate Normality of = thiosulphate Vol. of thiosulphate required

1 OA^

h. Standardisation of metabisulphite solution

25 ml of iodine solution (vii) will be taken in two 250

ml conical flasks (A & B). In A (blank) and B, 25 ml D.D.W.

and 25 ml metabisulphite solution (X) will be added. After

keeping flasks in dark for 5 min for reaction, titration will

be done with sodium thiosulphate till color become faint

yellow. Two ml starch solution will be added and titration

will be continued untill blue colour disappears which was

produced due to addition of starch. Titrstior' e

repeated to get constant readings and normality of

metabibihlphite will be calculated according to the following

formula:

(A-B) X N Normality of metabisulphite solution =

Vm

A = volume of sodium thiosulphate required for blank (flask A)

B = Volume of sodium thiosulphate required for metabisulphite

(flask B).

N = Normality of thiosulphate calculated earlier

Vm = Volume of metabiosulphite solution taken.

i. Working standard metabisulphite solution in absorbing

media

Now s o l u t i o n of metabisulphate w i l l be prepared of such

a s t r e n g t h t h a t 1 ml of s o l u t i o n c o n t a i n s 10 ug o f SO2 •

T o t a l y ug o f SOp in m e t a b i s u l p h i t e s o l u t i o n w i l l be

ca l cu la ted according to f o l l o w i n g formula:

1 0 5

Y = Normal i ty of metab isu lph i te x 32000

where Y i s t o t a l ug of SOg in metab isu lph i te s o l u t i o n :

Now w o r k i n g s t a n d a r d w i l l be p r e p a r e d i n 100 ml

abosr ing media such 1 ml = 10 ug SO2

10 X 100 Z =

Y

Z is the volume of metabisulphite required for dilution

to 100 ml with absorbing media.

j. Calibration of standard curve

Working standard metabisulphite will be pipetted in

graduated amounts (such as 0.1, 0.2, 0.3, 0.5, 0.7, 0.9, 1.0,

1.1, 1.2, 1.5 ml which will contain 1,2,3,5,7,9,10,11,12 and

15 ug SO2 respectively) into a series of impingers or

grauated nessler tubes. Absorbing media will be added to

tubes to make volume 10 ml. In the blanks 10 ml of absorbing

media will be added only. Then 1 ml sulphamic acid (ii), 2.0

ml formaldehyde solution (iii), 5.0 ml rosaniline

hydrochloric solution (iv) will be added one by one, and

after adding each, the solution will be shaken gently. After

it, the volume of each solution will be maintained with

D.D.W. up to 25 ml. After 30 minutes but befor 60 min., the

transmittance will be determined at 550 nm in

spectrophotometer. A standard curve will be drawn between

transmittance and concentration of ug SOg.

1 oe

k. Estimation

10 ml of sampled absorbing medium will be taken in

impinger. The 1 ml sulphemic acid, 2 ml formaldehyde solution

and 5 ml rosaniline will be added one by one and after

adding each, the solution will be shaken gently. After 30 min

but before 60 min transmittance will be determined at 550 nm

in specterophotometer. In the control (blank) in place of

absorbing media non-sampled medium will be taken. The ug of

SOg will be determined by placing of transmittanc^ i%

calibrated standard curve, the corresponding value (ug SOg)

will be found out. SOg ug/m will be calculated according to

following formula:

3 " 3 SO2 SO2 ug/m"* = X 10''

Volume of air sampled (lit)

Volume of air sampled = Flow rate of air x time of sampling

(minutes)

ug of SOg/m^ w i l l be converted i n t o ppm accord ing t o

the f o l l ow ing formula :

ug /m^ X 22400 ppm =

M X 10°

M i s the molecular weight of the p o l l u t a n t .

4 . Pathogenic i ty t e s t s

Pa thogen ic i t y of M. incogni ta, F. oxysporum f . sp .

ciceris, and R. bataticola {-Macrophomina phaseolina) a t the

i nocu l l um l e v e l s of 10,100,1000 and 10000 second s tage

1 O 7

juveniles (J2) and 0.5, 1.0 and 2.0g of mycelial suspension

per pot will be tested on six cultivars of chickpea and

soybean. The relative sensitivity of the cultivars of

chickpea and soybean to 0.1 and 0.2 ppm of SOg will also be

tested.

Plants in pots inoculated with the fungi will be kept

in greenhouse. Plants will be observed regularly for wilt

symptoms appearance and will be noted. The intensity of wilt

symptom, and wilting index will be determined after 15-30-

45-60 days of inoculation according to the following scale.

0 = No symptom

1 = Light symptoms

2 = Moderate symptoms

3 = Heavy symptoms

4 = Servere symptoms (dead) (Sidhu and Webster, 1978)

The relative amount of root-kot on a root system in

each treatment will be determined by scoring the extent of

disease on scale ranging a 0-5 scale (Reddy et al., 1979) as

given below:

0 = No root-rot

1 = 1-20% root-rot

2 = 21-40% root-rot

3 - 41-60% root-rot

4 - 61-80% root-rot

5 - 81-100% root-rot

1 oe

The following treatments will be inocluded for this

study:

T^ = Control

Tg = 0.5 g of mycelial mat per pot

T3 = 1.0 g of mycelial mat per pot

T^ = 2.0 g of mycelial mat per pot

Each treatment will be replicated five times. The same

treatments will be used for each cultivar.

Pathogenicity of M. incognita

Pathogenicity of root-knot nematode, W. incognita will

be tested using, 0, 10, 100, 1000 and 10000 Jg (per pot)

inoculum levels. Three week-old seedlings of six cultivars

of both crops will be inoculated in pots. Inoculated plants

will be kept in greenhouse for 50 days. At the time of

termination, plants will be uprooted gently and roots will be

washed with tap water, with care to avoid loss and injury to

the root system. Growth characters like lengths of root and

shoot; fresh and dry weights of shoot and root will be

recorded. Number of galls and egg masses per root system will

be counted. Gall index and egg mass indices will be rated

according to Taylor and Sasser's scale of 0-5 (Taylor and

Sasser, 1978). After determining GI and EMI, final population

of nematode for each cultivar will be determined by

determining numbers of eggs, female population in roots and

1 O S

soil population of the juveniles and males and Rf will be Pf

determined by Rf = (Oastenbrink, 1966). Treatments Pi

included for this study will be:

T Control

Tg = 10 Jg/pot

T3 = 100 Jg/ pot

T4 = 1000 Jg/ pot

Tg = 10000 J2/pot

The resistant and susceptibility will be allocated to

cultivars according to modified Canto-Saenez scheme (Sasser

et aJ., 1984).

Sensitivity to SOg

Relative sensitivity of all six cultivars of chick-pea

and soybean to SOg will be be tested at 0.1 and 0.2 ppm

SO2. Three-weeks-old seedlings will be exposed to SO2 in

exposure chambers every alternate days for 3 h. Exposing of

plants to SO2 will be continued for 75 days. At the end of

each exposure, plants will be transfered to the green-house.

Treatment are:

T = Control

T2 = 0.1 ppm SO2

T3 = 0.2 ppm SO2

All cualtivars of both crops will be treated and each variety

will be replicated five times.

1 1 O

5. Interact ion studies

a. Interact ion of M. incognita w i l t and root-rot fungi

I n t e r a c t i o n o f M. i ncogn i ta on c h i c k p e a w i t h F.

oxysporum f . sp. ciceris and on soybean w i th R. bataticola

{=M. phaseolina) w i l l be examined f i r s t . One suscept ib le and

one r e s i s t a n t c u l t i v a r t o the r e s p e c t i v e fungus w i l l be

s e l e c t e d c o n s i d e r i n g the r e s u l t s o f p a t h o g e n i c i t y t e s t s .

Three-weeks-o ld seed l i ng of t h e c u l t i v a r s Q-F bo th c r o p s ,

ra ised from sur face s t e r i l i z e d seeds in 30 cm <1 oott :<)

be i n o c u l a t e d w i t h J2 of the nematode. Fungal i n o c u l a t i o n

w i l l be done i n the form of mycel ium s u s p e n s i o n . The

inoculum leve l s o f the pathogens w i l l be se lec ted depending

upon the r e s u l t s of the pa thogen ic i t y t e s t s . The t reatments

w i l l be as f o l l o w

T^ = Control

T2 = Fungus

T3 = Nematode

T4 = F+N (Concomitant)

Tg = F+N (Sequent ia l , nematode 3-4 weeks p r i o r t o the

fungus) .

A f t e r i nocu la t i on of ch ick-pea and soybean c u l t i v a r s ,

the pots w i l l be kept i n greenhouse, and a f t e r a g row ing

per iod of about two months, p lan ts w i l l be removed from pots

and roots w i l l be washed to remove attached s o i l p a r t i c l e s .

1 1 1

Root gall index (GI) and egg mass index (EMI) will be rated

according to Taylor and Sasser's scale (Taylor and Sasser,

1978). In case of wilt fungus alone and the wilt fungus with

the nematode treatments, wilting indices will be recorded

according to Sidhu and Webster's (1978) scale. Root-rot

indices will be rated on 0-5 scale (Reddy et a/., 1979).

b. Interaction of SO2 with wilt and root-rot fungi

Interaction of SOp with F. oxysporum f. sp. ciceris on

chickpea and with R. bataticola {=M. phaseolina) on soybenr,

will be studied. Fungal inoculation of the seedlings will be

carried out as described earlier. Plants will be exposed to

SOg intermittently at the concentration of 0.1 ppm or 0.2

ppm, 3 h per exposures, every alternate days for about 75

days. The same varieties used for nematode-fungus interaction

studies will be used in this experiment as well. Soil pH will

be measured before starting of exposure and the time of

termination of experiments. Treatments for both the fungi

will be as follow:

T = Control (Unexposed, uninoculated)

Tp = SO2 exposed

Tg = Fungus unexposed

T^ = SO2 + Fungus

1 1 2

c. Interact ion of SOg with M. incognita

I n t e r a c t i o n of SO2 wi th M. incognita w i l l be s tud ied on

soybean and ch i ckpea . The p l a n t c u l t i v a r s used i n e a r l i e r

e x p e r i m e n t w i l l be used f o r t h i s s t u d y a l s o . A f t e r

i nocu la t i on the seed l ing , they w i l l be exposed to 0.2 ppm

SO2, 3 h per exposure every a l t e r n a t e day f o r 75 days. So i l

pH w i l l be measured before exposure to SO^ and a t the t ime of

t e rm ina t ion of experiments. Treatments w i l l be as f o l l o w s :

T^ = Contro l (Uninoculated, unexposed)

Tg = M. incognita (Unexposed)

T3 = SO2

T^ = SO2 + M. incognita

d. Interactions between SOg, wilt and root-rot fungi and M.

incognita

Interactions between SO2, F. oxysporum f. sp. ciceri&

and M. incognita on chickpea and between SO2, R. bataticola

and M. incognita on soybean will be studied. The levels of

inocula will be same as described earlier. Plants will be

exposed to SO2 every alternate day 3 h exposure for 75 days.

Soil pH will be measured before starting of exposure and at

the time of termination. Treatments will be as follows:

Unexposed set

T = Control

T2 = Fungus (F)

1 1 3

T^ = Nematode (N)

T4 = F+N (Concomitant)

Tg = F+N (Sequential, nematode 3-4 week prior to

fungus)

Exposed Set

Tg = Control

Ty = Fungus

Tg = Nematode

Tg = F+N (Concomitant)

T^Q = F+N (Sequential, nematode 3-4 weel prio. o

fungus)

In all above mentioned experiments, each treatment will

be replicated five times. An appropriate experimental design

will be used for each data will be analysed accordingly.

6. Laboratory Experiments

a. Effect of SO2 on hatching and mortility of M. incognita

Effect of SOp on hatching and juvenile mortility of M.

incognita will be studied is micro-exposure chambers. Ten egg

masses of relatively same size will be selected and will be

transfered to the small petriplates (3 cm) containing

sterilized. The petriplates containing egg masses will be

placed in micro-exposure chambers and will be exposed to

0.05, 0.1, and 0.2 ppm SO2, 3 h/day for six days. A set of

unexposed petri plates with egg masses will serve as control.

The number of hatched juveniles will be counted and hatching

1 1 ^

in relation to control will be determined. Observations will

be made after 24,48,92 and 184 h, number of motile and dead

will be noted in each observations. pH of water will be

measured before the starting of experiment and after total

exposures.

b. Effect of acidified soil on hatching and roortility of M.

incognita

Effect of acidified soil at pH levels of 7.0, 6.0, 5.0,

4,0, and 3.0 on hatching and mortality of M. incognita wi'l

be studied. Ten egg masses of relatively same size will be

transferred into the paper cups containing approximately 100

g of water washed sterilized sand. 25 ml of acidic solutions

prepared will be added to each cup. Observations will be made

8 days after addition of acidic solution. Number of mobile

and dead nematodes will be noted. Sand pH will be measured

before and after addition of acidic solutions.

7. Measurment of soil pH

To measure soil pH, soil suspension in water will be

prepared in the ratio of 1:10. To achive this, soil sample

will be crushed and mixed thoroughly. Then 10 g of soil will

be poured in 250 ml. Conical flask containing 100 ml. of

double distilled water and will be agitated for one hour. The

suspension will be filtered through filter paper and filtrate

will be used for the measurement of soil pH by glass

electrode.

1 1 5

8. Rais ing of seedl ings

Seeds w i l l be sown i n a mixture of s o i l , sand and farm

yard manure in the r a t i o of 2 :1:1 respec t i ve l y , contained in

30 cm c lay pots which are autocalved f o r s t e r i l i z a t i o n at 20

l b s . f o r 30 minutes. The s t e r i l i z e d pots w i l l be al lowed to

c o o l down a t room t e m p e r a t u r e b e f o r e u s i n g f o r t h e

exper iments.

Before sowing, seeds w i l l be surface s t e r i l i z e d w i th

0 . 1 % m e r c u r i c c h l o r i d e f o r 2 m i n u t e s and washed w i t h

s t e r i l i z e d water t h r i c e , t o remove t he t r a c e o f m e r c u r i c

c h l o r i d e . Seeds w i l l be sown in s t e r i l i z e d s o i l a t the ra te

o f f o u r seeds per p o t . F i f t e e n days a f t e r g e r m i n a t i o n ,

seed l ing w i l l be th inned to one in each pot . Three-weeks-old

s e e d l i n g s (approx . i n 4-5 leaves s t a g e ) w i l l be used f o r

t rea tments . Regular i r r i g a t i o n w i l l be done to keep up the

s o i l mois ture .

9. Rhizobium i n o c u l a t i o n

Seeds in all the experiments related to chickpea and

soybean will be inoculated with their respective strains of

Rhizobium before sowing. Commercial sugar and water will be

added in the soil based culture with thorough mixing. The

seeds of the test crops will be treated with this mixture

followed by the drying in shade for about half an hour before

sowing.

116

10. Parameters

The following parameters will be considered depending

upon the kind of experiments, for the potted plants, related

to interactions, pathogenicity etc.

Fresh and dry weights of shoQt and root

Length of shoot and root

Number of galls/root system

Number of egg masses/ root system

Gall index (GI)

Eggmass index (EMI)

Soil and root population of the nematode

Pf Reproduction factor (Rf = )

Pi

Total number of nodules / plant

Total number of functional nodules/ plant

Number of days for appearence of wilt symptoms

Wilt index at different intervals

Root-rot index (on 0-5 scale)

11. Root nodule bacteria

To assess the impact of selected pathogens, singly or

in combinations on root nodulation, functional, non­

functional and total number of nodules per root system in

each experiments will be counted individually. The pinkish,

healthy nodules will be considered as functional and others

as non-functional.

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