Volume 22(4), 13- 19, 2018 JOURNAL of Horticulture, Forestry and Biotechnology

www.journal-hfb.usab-tm.ro

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Physiological effects of treatment with fungicides in Prunus domestica L. attacked by Polystigma rubrum (pers.) Dc.

Nicolae I. 1*, Camen D.2, Bușe-Dragomir Luminița1

1University of Craiova,

2Banat University of Agriculture Sciences and Veterinary Medicine Timisoara

*Corresponding author. Email: ionnicolaebio@yahoo.com

Abstract Effects of treatment with fungicides on the physiological processes in Prunus domestica L. attacked by Polystigma rubrum (Pers.) DC. were performed on plum tree cultivated in the climatic conditions in Oltenia region.

The physiological analysis were performed on July 4th

2017, both for leaves of the plum tree treated with Dithane M 45 (0.2%), in five phases, at 10 days interval (May 9

th 2017, May 19

th 2017, May 29

th 2017, June 8

th 2017 and

June 18th 2017) and also for the leaves of the plum tree attacked by

Polystigma rubrum (Pers.) DC. in which have not been performed treatments (not treated with fungicide).

Following the analysis of the leaves of the plum tree, it has been noticed that the photosynthesis and transpiration intensity vary during the day according to climatic conditions, presenting lower values in the morning, higher values in the afternoon and lower values at night, but the recorded values are higher for the already analysed leaves of the plum tree after performing fungicide treatments, in comparison with the leaves of the plum tree attacked by the pathogen (not treated with fungicide). In the leaves of the plum tree analysed after performing treatments with fungicide it was registered a higher water content and clorophyll content, compared to attacked leaves by the pathogen where the decrease of the cellular turgescent and the deterioration of the chlorophyll already took place.

Key words fungicide, leaves of the plum tree, pathogen, physiological processes, Polystigma rubrum

Prunus domestica L. is a small tree of the

Rosaceae family which produces abundant white

flowers and fruits with high sugar content. The oval or spherical fruit varies in size, but

can be up to 8 cm across, and is usually sweet (dessert

plum), though some varieties are sour and require

cooking with sugar to make them palatable. Plums are

grown commercially in orchards, but modern

rootstocks, together with self-fertile strains, training

and pruning methods, allow single plums to be grown

in relatively small spaces. Their early flowering and

fruiting means that they require a sheltered spot away

from frosts and cold winds [4].

Red Leaf Spot of Plum is a common disease in

in years with rainy spring, especially in unprepared

orchards or old trees, causing defoliation, and the fruits

remain small.

The chemical treatments are applied at

warning signals, the first in the ascosporum design if

the plum is flanked, the temperature is 6 oC and the

rainfall is at least 0.1 mm and the others depending on

the rainfall, the source of the infection and the

susceptibility of the varieties [9].

The phytopathogenic fungus infections are

accompanied by structural changes and some changes

in the metabolism of host plant. This is necessary for

the coexistence of two partners involved, for a long

time and given the fact that they need to grow and to

reproduce, the parasite requires a constant supplywith

nutrients from the tissues of the host plant [5].

In Romania there were made numerous research concerning the biochemistry and physiology

of diseased plants. Antohe Anca and collab. carried out

a series of ecophysiological research in some sorts of

plum in the conditions of pesticides applications and of

the attack of Polystigma rubrum [1].

The physiological research regarding

photosynthesis intensity in Prunus domestica L. shows

variations between values of 13.6 - 14.4 μmol CO2 /

m2 / s [3].

The photosynthesis intensity depends on the

degree in leaves light exposure. The young leaves have

the highest intensity of the transpiration process and as

they get older, the transpiration intensity decreases, the

lower values being recorded at senescent leaves [2].

The increase of the temperature leaf,

photosynthetic active radiations and conductance

stomatal is positive correlated with the increase of the

photosynthesis and of the transpiration, but shows

variations in the attacked leaves as a result of several

structural modifications produced by pathogen [7].

The transpiration intensity and photosynthesis

during the day in the attacked leaves shows lower

values as a result of the reduction of the assimilation

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surface and malfunctioning of stomata opening and

closing mechanisms by the appearance of the yellow-

cream spots, then red-brown and in finally a necrosis of

the tissue corresponding spots [8].

Material and Method

The physiological research on the effects of

treatment with fungicides in Prunus domestica L.

attacked by Polystigma rubrum (Pers.) DC. were

performed in the plum tree cultivated in the climatic

conditions in Oltenia region.

The treatments with the fungicide Dithane M

45 (0.2%) was applied on the leaves in five phases at

10 days interval (May 9th

2017, May 19th

2017, May

29th

2017, June 8th

2017 and June 18th

2017) and the

physiological researches were performed on July 4th

2017, both for leaves of the plum trees treated with

fungicide and also for the attacked leaves of the plum

trees in which have not been performed treatments (not

treated with fungicide).

Dithane M 45 is a contact fungicide with a

wide action spectrum. It has a good persisting effect

remaining on the treated area from 7 to 10 days.

The estimate of the attack was made using the

calculation formulae by Săvescu & Rafailă [10].

The physiological processes (transpiration

intensity and photosynthesis) were determined with the

ultra compact photosynthesis measurement system

LCi, system which enables automatic recording and

other parameters (photosynthetic active radiations,

stomatal conductance, leaf temperature, etc.).

The dry substance and that of water contents

were determined by the gravimetric method.

The chlorophyll content was estimates by

Minolta SPAD 502 chlorophyll meter.

Results

For very good results in the application of

fungicides, the phenophase in which the plums and

climatic conditions are present must be taken into

account.

In the blossoming phenophases and the end of

the blossom there were the most favorable conditions

for the attack produced by Polystigma rubrum (Pers.)

DC. During this period, the amount of ascospores is

very high, and the leaflets are very tender.

The first symptoms of the attack produced by

the pathogen appear quite late from the infection,

usually the end of April, the beginning of June.

The disease (Red Leaf Spot of Plum) produced

by Polystigma rubrum (Pers.) DC. is manifested on the

leaves through approximately circular spots make their

appearance, at first yellow, then orange and finally

turning into red-brown (Fig. 1 and Fig. 2).

The tissue corresponding to spots, is

prominent, waxed and on the underside of the leaf

there are punctiform formations that represent ostioles

of the picnidia of the pathogen agent [6].

In the years favorable to the disease, as a

result of intense attacks, the dry leaves and fall; this

causes a low resistance of trees during the winter.

Fig. 1. The leaves of plum tree (Prunus domestica L.)

attacked by Polystigma rubrum (Pers.) DC. -

(the upper epidermis of the leaf) - Original.

Fig. 2. The leaves of plum tree (Prunus domestica L.)

attacked by Polystigma rubrum (Pers.) DC. -

(the lower epidermis of the leaf) - Original.

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Fig. 5. The transpiration intensity of leaves of the

plum tree (Prunus domestica L.)

Polystigma rubrum (Pers.) DC. shows the

mycelium with intercellular development which forms

colored stroma corresponding to the colored spots on

the leaves. It differentiates the fungus asexuate

fructifications of the pathogen: picnidia with

picnospores hyaline, unicellular, filaments.

In autumn perithecia are formed which

contains asca with ascospores ellipsoidal, unicellular,

hyaline.

The physiological analyses were performed on

July 4th

2017, both for leaves of the plum trees treated

with Dithane M 45 (0.2 %) fungicide and also for the

attacked leaves of the plum trees in which have not

been performed treatments (not treated with fungicide).

The estimation of the attack (frequency,

intensity and degree of attack) caused by Polystigma

rubrum (Pers.) DC. at the leaves plum tree is presented

in Fig. 3.

The diurnal dynamics of photosynthesis

intensity in the leaves of the plum tree attacked by the

pathogen is similar to that in the leaves of the plum tree

in which treatments have been performed, but the

recorded values are lower in comparison with these as

a result of the reduction of the assimilation surface, as

well as the inhibition of several biochemical reactions

of the photosynthesis (Fig. 4).

The diurnal dynamics of transpiration

intensity in the attacked leaves is similar to that in the

leaves in which treatments have been performed, but

the recorded values are lower in comparison with these

as a result of the yellow or red-brown spots that then

become crusty and the malfunctioning of the stomatic

apparatus (Fig. 5).

Fig. 4. The photosynthesis intensity of leaves of

the plum tree (Prunus domestica L.)

Fig. 3. The estimation of the attack in the Prunus domestica L.produced by

Polystigma rubrum (Pers.) DC.

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The transpiration intensity and photosynthesis

intensity are correlated with the physiological

parameters (leaf temperature photosynthetic, active

radiation, and stomatal conductance), but present

different values in the leaves of plum tree in which

treatments have been performed, in comparison with

the leaves attacked by the pathogen, a strong

association between these being established.

A result of physiological research carried out

at the leaves of the plum tree it can be observed an

increase of the physiological parameters, increase

starting in the morning; they present higher values at

after noon and a gradually decrease towards evening

(Table. 1).

Table 1

The physiological parameters registered in the leaves of the plum tree.

Linear regression made between the

photosynthetic active radiations and photosynthesis

intensity show a positive correlation, the coefficient of

determination (R2) was 0.97 for the leaves of the plum

tree in which treatments have been performed and 0.96

for the attacked leaves of the plum trees in which

treatments have not been performed (not treated with

fungicide). Linear regression made between the

photosynthetic active radiations and transpiration

intensity show a positive correlation, the coefficient of

determination R2 was 0.90 for the leaves of the plum

tree treated and 0.93 for the attacked leaves by the

pathogen (not treated with fungicide) - Fig. 6 and Fig.

7.

The physiological

parameters

The leaves of the analyzed plants The hours of the analysis performing

and the recorded values (July 4th

2017)

900

1100

1300

1500

1700

The photosynthetic

active radiation

(μmol / m2 / s)

The leaves of the plants after treatments

with fungicide 1127 1356 1572 1540 1434

The leaves of the plants attacked by pathogen

(not treatments with fungicide) 1092 1310 1455 1386 1358

The leaf

temperature

(oC)

The leaves of the plants after treatments

with fungicide 27.5 31.2 35.8 35.4 34.2

The leaves of the plants attacked by pathogen

(not treatments with fungicide) 27.4 30.5 35.7 35.2 33.7

The stomatal

conductance

( mol / m2 / s)

The leaves of the plants after treatments

with fungicide 0.07 0.09 0.13 0.12 0.11

The leaves of the plants attacked by pathogen

(not treatments with fungicide) 0.05 0.08 0.12 0.11 0.08

Fig. 6. The correlation between the photosynthetic

active radiation and the intensity of photosynthesis in

the plum tree (Prunus domestica L.).

.

Fig. 7. The correlation between the photosynthetic

active radiation and the intensity of transpiration in

the plum tree (Prunus domestica L.).

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Linear regression made between the leaf

temperature and photosynthesis intensity show a good

positive correlation, the coefficient of determination

(R2) was 0.95 for the leaves of the plum tree in which

treatments have been performed and 0.94 for the leaves

attacked by the pathogen (not treated with fungicide).

Linear regression made between the leaf temperature

and transpiration intensity show a good positive

correlation, the coefficient of determination R2 was

0.95 for the leaves of the plum tree treated and 0.93 for

the attacked leaves in which have not been performed

treatments (not treated with fungicide) - Fig. 8 and Fig.

9.

Linear regression between the stomatal

conductance and photosynthesis intensity show a

positive correlation, the coefficient of determination

(R2) was 0.89 for the leaves of the plum tree in which

treatments have been performed and 0.82 for the leaves

attacked by the pathogen (not treated with fungicide).

Linear regression made between the transpiration

intensity and stomatal conductance show a positive

correlation, the coefficient of determination R2 was

0.87 for the leaves of the plum tree treated and 0.72 for

the attacked leaves (not treated with fungicide) - Fig.

10 and Fig. 11.

Fig. 8. The correlation between the leaf temperature

and the intensity of photosynthesis in the

plum tree (Prunus domestica L.).

Fig. 9. The correlation between the leaf temperature

and the intensity of transpiration in the

plum tree (Prunus domestica L.).

Fig. 10. The correlation between the stomatal

conductance and intensity of photosynthesis in the

plum tree (Prunus domestica L.).

Fig. 11. The correlation between the stomatal

conductance and intensity of transpiration in the plum

tree (Prunus domestica L.).

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After performing treatments with fungicide at

the leaves of the plum tree analysed it was registered a

lower dry substance content and a higher water content

to the leaves of the plum tree attacked by the pathogen

(not treated with fungicide) - Fig. 12.

After performing treatments in the analysed

leaves with fungicide a higher chlorophyll content is

registered, compared with the leaves of the plum tree

attacked by Polystigma rubrum (Pers.) DC. where the

reduction of the chlorophyll biosynthesis and the

deterioration of the chlorophyll already took place (Fig.

13).

Conclusions

It was observed that during the day in the

plum tree (Prunus domestica L.). the photosynthesis

intensity and transpiration intensity vary according to

climatic conditions, presenting lower values in the

morning, higher values in the afternoon and lower

values at night, the recorded values are higher for the

after performing fungicide treatments, in comparison

with the leaves of the plum tree attacked by the

pathogen (not treated with fungicide).

The intensity of the transpiration and intensity

photosynthesis are correlated with the stomatal

conductance photosynthetic active radiation, and

theleaf temperature, but in the leaves of the plum tree

presents different values in which treatments with

fungicides have been performed, in comparison with

the leaves infected by the pathogen (not treated with

fungicide), a strong association between these was

established.

At the analysed leaves of the plum tree it can

be observed that is a positive correlation between the

photosynthesis intensity and the clorophyll content.

Of the plum tree leaves analysed after

performing treatments with fungicide it was registered

a higher chlorophyll content and water content, to the

leaves of the plum tree attacked by Polystigma rubrum

(Pers.) DC. where the decrease of the cellular

turgescent and the deterioration of the chlorophyll

already took place with consequences over the pear

production.

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