Host Reactions of Mechanically Transmissible Legume ... · Host reactions of mechanically...

Etiology

Host Reactions of Mechanically Transmissible Legume Viruses of theNorthern Temperate Zone

R. Hampton, L. Beczner, D. Hagedorn, L. Bos,T. Inouye, 0. Barnett, M. Musil, and J. Meiners

Authors are members of the International Working Group on Legume Viruses: respectively, Research PlantPathologist, Agricultural Research Service, U.S. Department of Agriculture, Oregon State University, Corvallis, OR97331; Plant Virologist, Research Institute of Plant Protection, Budapest, Hungary; Professor, Department of PlantPathology, University of Wisconsin, Madison, WI 53706; Virus Research Officer, Institute of PhytopathologicalResearch, Wageningen, The Netherlands; Plant Virologist, College of Agriculture, University of Osaka Prefecture,Sakai, Osaka, 591, Japan; Associate Professor, Department of Plant Pathology and Physiology, Clemson University,Clemson, SC 29631; Plant Virologist, Institute of Virology, Slovak Academy of Sciences, Bratislava 9,Czechoslovakia; and Chief, Applied Plant Pathology Laboratory, Agricultural Research Service, U.S. Department ofAgriculture, Beltsville, MD 29795.

Contribution of The Agricultural Research Service, U.S. Department of Agriculture, in cooperation with theAgricultural Experiment Station, Oregon State University, Corvallis. Technical Paper 4594 of the latter.

Accepted for publication 30 December 1977.

ABSTRACT

HAMPTON, R., L. BECZNER, D. HAGEDORN, L. BOS, T. INOUYE, 0. BARNETT, M. MUSIL, and J. MEINERS. 1978.Host reactions of mechanically transmissible legume viruses of the northern temperate zone. Phytopathology 68: 989-997.

Reactions of 23 plant hosts to inoculation with each of 38 hosts. The final key formulation was derived fromlegume viruses, and a key to aid in the diagnosis of these evaluations of all possible combinations and hierarchies ofviruses, are presented. The virus isolates, investigated at lo- plant hosts. Assuming that each virus will infect and inducecations where they are indigenous, were either type cultures characteristic symptoms when inoculated into definedor had been equivalently characterized. Each of the hosts was cultivars under suitable conditions, the key is an aid toderived from standardized seedstocks. Therefore, each identification for each of the 38 viruses tested. Evaluations ofinvestigator tested specific viruses against identical host two to four separate isolates of certain viruses supported thegermplasm. The key is based on some 1,700 symtomatologi- diagnostic value of the key.cal data and virus host ranges obtained from selected plant

The diverse plant family, Leguminosae, includes at significantly expressed as observable virus interactionsleast 35 species cultivated for protein-rich food, feed and with specific hosts. During this same era, several workersforage, and green manure. Crop losses in Phaseolus beans independently have developed sets of host differentialsdue to virus infection were reported as early as 1917 (8), for diagnosing certain indigenous legume viruses.and the destructiveness of virus-induced legume diseases Diagnostic information, however, usually has beenhas become increasingly apparent since that time. Weiss published only for individual viruses, sometimes(11) pioneered in classifying viruses infectious to legumes communicated comprehensively only among colleagues,by host range and symptomatology, and later (12) and with a few exceptions (2, 4, 5) has lackedcompiled host relations for viruses described primarily on standardization or international scope.leguminous crops. Bos and van der Want (3) proposed The International Working Group on Legume Virusesresearch on legume viruses collectively. Bos et al. was established in 1962 to promote international com-(2) suggested standardized procedures for identifying cumication and cooperation among plant pathologiststhese viruses, and later Bos (1) published an updated working with legume viruses and to standardize identifi-compendium of viruses naturally infectious to legumi- cation criteria and nomenclature for these viruses. Thisnous plants. working group recently published a revised list of host

Over the past 25 yr, an era of increasing emphasis on plants proven valuable for definitive work with legumecontrolling virus-induced diseases of Phaseolus and viruses (9). We recognize, however, that significantPisum crops in the USA , Europe, and Japan, new differences in virus sensitivity and growth habit existtechnology facilitating virus purification and among selections of virus indicator plants (10), and thatcharacterization has dramatically enhanced plant virus widely applicable information on virus-host interactionsidentification. Although there has been a strong emphasis is dependent upon standardized test-plant seedstocks. Arecently on intrinsic viral properties, it now is being repository of reference seedstocks (6), including some 93recognized increasingly that viral genetics are plant types of the Plant Virus Indicator Collection (7),

now has been established at Fort Collins, CO, USA (see00032-949X/78/000 173$03.00/0 Materials and Methods, Plant hosts).Copyright © 1978 The American Phytopathological Society, 3340 The present study was undertaken to standardize hostPilot Knob Road, St. Paul, MN 55121. All rights reserved, ranges and reactions for type cultures of important

989

990 PHYTOPATHOLOGY [Vol. 68

legume viruses of the northern temperate zone on workers with limited laboratory facilities or as

uniform plant hosts, and to formulate a key to aid in the supplementary information for well-equipped workers.

diagnosis of these viruses. We recognize that current We expect users of our key to depend, for final virus

diagnostic procedures typically consist of the identification, upon confirmatory ultrastructural,

development of preliminary host-reaction information, serological, and, when necessary, physico-chemical

determination of virus particle morphology, and properties of virus isolates.

serological identification. When ambiguities or newviruses are encountered during such information MATERIALS AND METHODS

development, however, new or reinforcing lines ofevidence are required. Host reactions developed by this Plant hosts.-The 23 plant hosts tested in this study are

investigation are intended as preliminary guidelines for described in Table 1. They comprise 19 species, 17 genera,

TABLE 1. Uniform plant hosts that were tested against 38 legume virus isolates.

Host species Cultivar/Selection NSSL Accession no.a

Antirrhinwn majus L. Mixed Colors(Tetra Giant Ruffled Mixed) 92506

Chenopodium anaranticolor Coste & Reyn. Corvallis strain 93611

Cucumis sativus L. Chicago Pickling 92507

Datura strcanonium L. R. Fulton strain 93613

Glycine max (L.) Merr. I Bragg 90508

Glycine max II Davis 90509

Gomphrena globosa L. A. F. Ross strain 93612

Lycopersicon esculentuam Mill. Marglobe 92508

Medicago sativa L. DuPuits 92509

Nicotiana glutinosa L. Corvallis strain 91533

Nicotiana tabacum L. Samsun NN 90496

Petunia hybrida Hort. Vilm.-Andr. King Henry 96919

Phaseolus vulgaris L. I Bountiful 89342

PhaseoZus vulgaris II Black Turtle Soup 92518

Phaseolus vulga2rs iII Pinto I1 89343

Phlox drnmondii Hook. Tall Mixed Colors 92510

Pisum sativum L. I Perfected Wales 92511

Pisum sativwn II Dark Skin Perfection 92512

Spinacea oleracea L. Bloomsdale Long Standing 92513

Trif'olium pratense L. Kenland 92514

Trifoliun repens L. New Zealand 92515

Vicia faba L. (minor) Bell bean 92516

Vigna unguiculata (L.) Walp. California Cowpea #5(Early Ramshorn,California Blackeye #5) 92517

aSeedlot accession numbers for reference samples kept at the National Seed Storage Laboratory,

Fort Collins, Colorado 80521, U.S.A.

July 1978] HAMPTON ET AL.: NORTH TEMPERATE LEGUME VIRUSES/HOST REACTIONS 991

and seven plant families, and were chosen for phenotypes. Seedlots of the plant hosts were gathered atdocumented value in detecting or distinguishing certain one location, subdivided into eight equal quantities forviruses. In a few cases (Antirrhinum, Petunia, Phlox) they distribution to the eight investigators and into a reservewere selected merely on the basis of commercial supply. Thus, each investigator tested documentedavailability of seed representing standardized host isolates of viruses on plant host germplasm identical to

TABLE 2. Legume virus isolates tested against 23 uniform plant hosts.

Virus Selected synonym Isolate/Cooperator

Alfalfa Mosaic Lucerne mosaic virus Necrotic strain, Beczner / (2,5,8)1

Adzuki Bean Mosaic AB-S / (6)

Bean Cosmon Mosaic Phaseolus virus I Westlandia strain (- type strain)/ (3)

Bean Pod Mottle Beltsville strain / (7)

Bean Southern Mosaic Bean mosaic virus 4 Beltsville strain / (7)

Bean Yellow Mosaic Phaseolus virus 2 B-25 strain, Bos / (3,5,8)

Bean Yellow Severe Mosaic Gil-6 strain, Hampton / (5)

Broadbean Wilt P.O. pea streak virus Beczner isolate / (2)

Clover Blotch CBV 1 isolate/ (8)

Clover Yellow Mosaic Pea mottle virus Casper strain / (2)

Clover Yellow Vein Pea necrosis virus ATCC PV-123 / (1)

Clover (Red) Mottle TpM 25 isolate / (8)

Clover (Red) Necrotic Mosaic TpM 34 isolate / (8)

Clover (Red) Vein Mosaic Wisconsin pea stunt virus RK 31, Hagedorn / (3,4,8)

Clover (White)Mosaic Trifoliwn virus 1 Wageningen strain, Bos / (2,5,8)

Cowpea Aphidborne Mosaic Cowpea cosmon mosaic virus Florida straiti, Purcifull & Zettler / (1)

Cowpea Chlorotic Mottle Type culture, Kuhn / (1)

Cowpea Mosaic Cowpea yellow mosaic virus Yellow strain, Agrawal / (I)

Cucumber Mosaic Cucumber virus 1 P 146 / (6)

Desmodium Yellow Mottle Type culture, Scott / (1)

Lettuce Mosaic Lactuca virus 1 69-053 / (6)

Pea Dwarf Mosaic (Related to broadbean wilt) P 108 / (6)

Pea Early Browning Vroege-verbruiningsvirus van erwt E 116, Bos / (3)

Pea Enation Mosaic Pisur virus 1 Madison strain, Hagedorn / (4)

Pea Seedborne Mosaic Pea leafroll mosaic virus C 4-26 / (5,4)

Pea Streak Sweet clover virus Wisconsin strain, Hagedorn / (3,4,5)

Peanut Mottle Groundnut mottle virus M 2, Kuhn / (1)

Peanut Stunt Groundnut stunt virus Raleigh strain, Hebert / (1)

Soybean Mild Mosaic SV-115, Takahashi / (6)

Soybean Mosaic Soybean virus 1 Madison strain, Hagedorn / (4)

Soybean Stunt SSV-A, Takahashi / (6)

Tobacco Ringspot Nicotiana virus 12 Demski isolate / (2)

Tobacco Streak Nicotiana virus 8 Red node strain, Beltsville / (7)

Tomato Black Ring Lettuce ringspot virus Schmelzer isolate / (2)

Tomato Spotted Wilt Lycopersicum virus 3 Corvallis strain / (5)

Turnip Mosaic Cabbage black ring virus PN-9 / (6)

Watermelon Mosaic Muskmelon mosaic virus Molnir isolate / (2)

Wisteria Vein Mosaic Ws 2B, Bos / (3)a Numerical reference to cooperators testing viruses for this study. Strain designated was selected as

representative; results presented in Table 1 were contributed by first designated cooperator.Cooperator reference numbers are ae follows: Barnett (i), Beczner (2), Bos (3), Hagedorn (4),Hampton (5), Inouye (6), MNiners (7), and Musil (8). Results presented in Table 3.


Table 3. Symptoms induced in 23 plant hosts by 38 legume virus isolatesLEGEND: 0 4J

., U. '.4 0 05

cc E .' s, Sa 3 4 4 -4

Local Symptoms 0 '4 4

Ia S -4 4 4 0 1- a 1

Anir amsMa * - a -" -r'.

Systemic Syapt. LL ' - 4 -*4 - NS 4 a1 a L - L

MoMac)a ~ .- -* -* MoLC, MoMa V4h Moa (VB)4 -.4 4.

HOST PLANT .44 0 4 s c > > >a ~ ~ý a>ý ~ 4 4 -44

N U

t ai . .. . 1 L--Antirr.o -* -* --M0 s -

Chen. amarant. LL _, _ -S LLn LL Chl - LL1Mo,Ma -* -* - MoLC, MoMa, VChl Mo (VB) -

N N

Cuc. sativus L - - - Chl Z - - LLc

VCMo - - - - * - - Chl a s

Dat. stramon. LL -*.R ?

VCMo -* - - - o - Mo - - -

Ma

Glyc. max I LL - 1 . LLc ? LLn LLc - 1 LLn,RSn LLn

Mo - Mo Mo VB,VC Mo,NS Mo Chl MoVC VChl,Chl ChlMo

Glyc. max II LL -. LL ? - LLc 1 LLn

W,N - MoStu Mo VN,LC, Mo Chl MoVC VChl,Ma ChlMoStu

Gomph. glob. RSn - ? - - LLn (LLn) LLn LLn

Mo _ * - LC,Mo s

Lycop. escul. LL- _ _ _ - 1-_Mo,NS -* -* - -* - s (VC) -

Medic. sativa -.,-.-_- LLn 1 .

S -* . - Mo Mo, RSc No

Nicot. glut. LL 0 0 LLc RSn 1 - RSn

No 0 0 Mo,RS Mo (s)

Nicot. tab. - - LLn LLn,RS RSn - RScNS RSn

Mo,Ma -* -* - - -* Mo Mo - (s)

Petunia hyb. LL -* 0 - 0 - LLc (RSn) - RSn

VCMo -* 0 - 0 - VCo Mo - ? (s)

Phas. vulg. I a LL LLr LU.VN LLC LLc LLn LLn ChlS z LLc LLn,Chl LLn.VN- - Mo,Ma Mo Mo MoMa, Stu Ep,N - Mo,Ma s ChlS N

Phas. vulg. I1 LL . LLc RSn,LC - VN LLn LLn, ChlS 1 LLc LLnVN LLn,VN- - Mo s No VN,Mo, Ep,N - Mo,Ma Ho Mo,Stu - N

Ma,StuLln,

Phas. vulg. II a LL - LC.VN LL, VN 1 n Lln 4 VN.VB t t LLnVN Chl.VN- - - s s ChlS Ep,N - Mo,Ma s ChIS - N

Mo,Stu

Phlox drum. RSLL 0 - - 0 - - -

Mo,Str 0 * - 0 - - -

Pisum sat. I L . - - - LLc LLc LL, LLn

o - -* - MoStu Mo,N VC,Mo Chl Chl,Stu Str

Pieu sat. II NS - LLn - LLc " LLnVN

VCMo -a - -,- MoN VCMo Stu,N Str

Spin. oler. LL .* -- LLn t l(ChlS) L~c - ChlS.-• -* -* - - -* Mo,Stu - Mo,LR, -

Stu

Trifol. prat. t L__1* - 1 I N LLc -

MoMa -* - s No No - o Mo,Ma

Trifol. rep. I -* z z -

Mo,Ma -* s Mo oo

Vicia faba LL - - I IN Lin LLn NS (NS)

Str,N -* - s VC,Mo NS,N Mo No VCMo Mo, Stu, N Chl(NS) RSn

Vigna unguic. LL LL - - 1 Z " hlS 5 t RSn LLVN

- o Mo s s - VCMo Mo,Ma - - Chl


TABLE 3, Contd.

Local Symptoms - U W,. 4 4 to U10 U 4 4 14 0 w '4 a 1Systemic Syma pt. a - .l o -* w 4J LL'- 4 '-" 44 bo .- UU 1o0

.4 ccU ., 4HU 0 WU kO O4 ai

Chn Oaat . w L n LLa LL LL L~ L~ La

-H w -0 VCS -A , hS -4) w'o c, 0 0. 0 ~ 0. 0..0

Cuc. 8ativus ___ LLc - - LL ___ -. -* L --- - hS -*- - -*

VC,Mo

- - - 1___ __ _ -* - -* LL l - - ____Dat. strwnon. - - - -M

Glyc. mar I - / LLn LLc _ LLn - -* 1 0 - -

o - - V - Mo - Mo 0 - (w)

yc. I I LLm . LLn - -*

y.Mo Mo Mo - V -

Gonrph. glob. LL LLc,RSc I -* LL -* LUn LLc - LLn-* - sa s a Mo a NS Mo - Mo -

Lycop. escul, - LLc - -* - -* I .- - - -- MoMa, -* -.. . .-*Stu

Medic. sativa LI -* - -* -* L- .*

s Mo - - - so --* • -* LL

Nicot. glut. - VC,Mo, -* RSc 0 - - 0

Mda, Stu

- - - 1 1 -* - -* 1 RS - - -Nicot. tab. -VCMo -* - Str -

olc max I -L-* L- -n 0

Peturz•hyb. o -*CM - - ~ 0

so VCMoMo

Pha. vulg. I t t Lc LLc LL -* LL 0n

- Mo ChMS M0 VC,LR - -* 0Sor

Mo, Stu RSc

Phah. vulg. II Lc t LL LLn 0 - I- Mo Chi Mo Mo VC,Mo,--N Mo - RSc,LC 0- -

Stu

Pas. vuig. IIl - LLc LLc,VN RSc,VN - LLc - LLn

- Mo Mo,Str VC,Mo, Mo - RS,Mo,Stu LC

Phlor drum. " I _ -* I -* - RS -

- -a b, Mo • -* MO S

Pisum sat.I I LLc - -- -* - - LIL Chi WVB,Ma, Mo,L - -- VC,VB, - VC,Mo VC,Mo, LR,VC Mo),Ma LR,Stu VB,Ma,Stu, Str Mo Ma, Stu M N

Pisum sat. II t LLc L c -* LLn Ch l W, Mo,LR IlS VC,VB, VC,Mo VC,Mo, LR,VB Mo,Ma LR,Stu VB,Ma,

Stu,Str Mo Ma,Stu N

Spin. oler. I - I I LLc LL - -* - - -- Chl 0 Mo VC,Mo I-* VC,•Mo, . -

MaStuN

Tirifol. prat. I - I - -* - 0(VC,Mo) Mo - - - - -- - - -0TPifol. rep. - - "- * . -* -* - -(1 _

S, Str Mo - is - - - - s -- -

Vicia saba L e LLn LLn LL - * Lwn

VC,Str Mo Mo - sa MS or - - VC,Mo, a - LR,Mo, MoStrMo Stu N

Si-n. o i. Lc LLc LL LL -

V u -* VC,Mo VB,Stu, Mo Mo VC.Mo a - - -*chli Suu


TABLE 3, Contd

LEGEND: A '0

0j - 4 U J 0d 40 c

Local S ,,toms 4- U 4. 4 w oSystemic Sympt. a .,4

4-4 4-4 9.. 0U 0.0 0 14 w4o 00

, > . .0 00 0 .0 4.4 00 0 ~ 0 a 0 -4

HOST PLANT 4

9

LLc -0 LLn,(RS) - .L_ -L__Antirr. majus Mo Mo O MoNS - s --

C a LLc LL LLc LL LLn - -* LL LLn LLcChn.•at.-

VC,ChlS- VB ChiS, - -* Mo,Ma - - - CCl

VC ,Mo

_civ_ LLc LL _. LLc LLc _ _* -Cuc. hativus Ch Mo,RSc - - VC,Mo MO Mo Mo - - VC,Mo -*

- LL LLc - LL -*

Dat. tramon. Mo - - Mo Mo Mo,Ma - -*

Glyc.max I LLc LL VN.Mo LL LLn - -1- LLn

VB,RSc VC,ChlS VNM,Mo VCMo NSuMO, MO Mo -

G_~~maII 1_ LL VN.ChI LL LLc - _ _-*

y as Vc,ChlS Mo,Ma VC,Mo, NS,Mo Mo Mo -* -

Mo,Ma Stu Stu

Gomph. glob. LLc L LL 1 LL L _ _ __S ChS - - s -1s (Ma,W) - -

Lyo. .- _* LLn LLn,RS LLc - -

Lycop. escul. -. Mo...- - Mo, Ma,RSn

Medic. sativa - 0 - -

- 1 LL - - LLc LLn LL 0

Nicot. glut. _ Mo VC,ChlS - VC,Mo, I - s NS,N VC,Mo, 0

ChlS NS,Stu

Nicot. tab LL LLn - LLn,RS LLn LL 1 1

- ,W - VC,RSc RS - VCMo, M - -Mo ChlS NS

Petunia hyb. - __ -* 1 • - LL LL - 0- VC,Mo VC,Mo VC VC,Mo, Mo - MO -* VC,Mo, - 0

ChiS NS,Stu

LLc,VM LLcEp - LLc - LL VNEp LLc - * • LLnPha.s Mo,Ma - - NS,N Str NS,Mo, " -

Ma

.vg LLnV LLcEp LL LLUnVN - LLn VNEp LLn - -*

Ca...,Itr, Mo,Ma - " LR,Str, Str MO - -

N NS,Stu

Phas. vulg. II L2c Ep LL LLc - LLn VNEp LLe -* -

Chi Mo,Ma - - LPStr, Str NS,Mo - - -

NS,Stu

LLc, LE LLn - 1 - -

Phlox drum. StrMa L

- Str,VN, _ _ - NS,Mo - -

Mo

Pisen sat. I • _ 2 LLn -, LLc,LR - - -

VB,Mo Ma,Mo Mo,Stu VC - Mo - "

f- z - LLc _, LL, - -*

Fwn eat. II VB,Mo Ma,Mo VC,Mo, s Mo Mo - -

Stu

LLc L 1 LLc - - LL LLc 1Spin.ChS, VC, -* VC,Mo, - - ChS, -

Mo,Ma ChIS LR,Stu Stu,N

Trifol. prat. • - - "* £ - - -* - -. -. - .- - _

- s

._ _ 1 .* -* 1 . .. .- -

Trifol. rep. _ -- -. .. ..

LLn N z Chl.LLc -* LL . L . LVicia faba Mo MoRSc s - Mo - - - s Mo ChIS

Vigna unguic. £ LLc LL LLe LL LLn,RS LLc -

Mo VB,Mo VCMNS, Mo - Str,N Mo LR VC, - -

Stu Stu


that employed by the other investigators. The reserve three times, the last time after casual observation hadsupply of each plant host seedlot was deposited in the indicated a steady-state host response to inoculationSeedbank for Plant Virus Indicators (see Table 1 for (Table 3). Anomalous symptoms which were observed inaccession numbers) at the National Seed Storage noninoculated control plants of Petunia, soybeans, andLaboratory, Fort Collins, CO 80521 USA, under the care tomato at some locations, when tested as possibly havingof L. N. Bass. been induced by seedborne viruses,were found not to beTo the extent possible, 10 plants of each of the 23 hosts pathogen-induced, and were discounted from thewere inoculated simultaneously with a given virus. symptomatology of inoculated plants.Simultaneous inoculation of the 23 plant hosts was Unless otherwise designated, instances of systemicfacilitated by coordinated plantings of hosts according to latent infection were determined and recorded. For thisthe time required from seed planting to the development purpose, plants that had remained free of symptomsof a usable plant (varied from 2 to 5 wk). Rapidly approximately 7 wk after inoculation with a given virusdeveloping species usually were inoculated on fully were assayed (back-inoculated) on another host of provenexpanded primary leaves; more slowly developing species sensitivity to that virus. Most investigators did not test forwere inoculated on secondary leaves on the fourth to localized latent infection, and a negative reaction foreighth nodes. Several vigorous, healthy plants of each inoculated leaves was used therefore to designate absencehost were maintained as buffer-abraded, noninoculated of symptoms rather than absence of virus.controls during each test period. Soil mixtures, fertilizers, For the purpose of formulating a key from host rangeand cultural practices which promoted optimal growth and symptomatological information supplied by the eightand vigor of plant hosts were employed at each location, investigators, data were entered into punched cards under

Virus isolates.-Thirty-eight virus isolates, described two virus-host interaction categories: definitivein Table 2, were investigated. Each investigator tested symptoms induced (localized or systemic or both:isolates that were indigenous to his area and were "positive") or symptoms not induced ("negative").recognized as typically representative of a known virus. Missing or inconclusive data were entered into the cardsThree separate isolates of five viruses (alfalfa mosaic as color codes. Various selections and arrangementsvirus, bean yellow mosaic virus, red clover vein mosaic (hierarchies) of hosts and formulations of trial keys werevirus, white clover mosaic virus, and pea streak virus) evaluated by card sorting. The key finally accepted waswere investigated. The other 33 viruses were represented formulated on three basic premises: (i) the numbers ofin this study by single isolates. In most cases, isolates plant host hierarchies should provide adequate hosttested had been documented in publications, and many germplasm by which to test and differentiate viruses ofare regarded as type cultures. Reference sources of these distinctive pathogenic capabilities, (ii) strategic hosts toisolates, in the form of desiccated, infected plant tissue, be arranged in the hierarchical system should be selectedwere prepared by the investigators. Inoculum was which both divide the 38 viruses into approximately equalprepared from plants previously determined to be groups and respond to inoculation by these viruses bysatisfactory propagation hosts. producing distinctive and reliable symptoms, (iii) to the

Inoculation procedure.-Host plants were inoculated extent possible, within the limits of missing orby mechanical abrasion of the upper leaf surface, inconclusive data, hosts should be selected which haveMechanical inoculation was facilitated by dusting silicon been acknowledged, historical differential hosts for well-carbide powder onto the leaf surfaces before inoculum known viruses.application. Specific buffers, tissue extractions, and Greenhouse test environment.-Environmentalinoculum application methods were left to the discretion conditions varied significantly among the eight locationsof each investigator. Inoculum infectivity, but not virus at which cooperative tests were undertaken, although theconcentration, was monitored by investigators during northern latitude of test locations varied only from 340this study. 40' at Clemson, SC, USA to 510 58' at Wageningen, The

Symptomatology.--Host plants were observed for 3 to Netherlands. Five of the locations were dominated by7 wk after inoculation for the development of localized island or coastal climates, whereas three locations wereand/or systemic symptoms. Virus-induced symptoms dominated by less-temperate continental climates. At allwere categorized and recorded under 24 descriptive locations, however, winter greenhouse environmentssymbols previously agreed upon by the investigators, were somewhat comparable in temperature (16 to 22 C),Leaves of noninoculated control plants were observed to photoperiod (10 to 13 hr), and solar radiation intensitydistinguish between virus-induced symptoms and aging (80 to 180 langleys). Tests undertaken at one location inor other anomalous effects. Inoculated plants were May and June were exposed to temperatures of almost 40scrutinized for localized and systemic symptoms at least C and a 14-hr photoperiod. The effects of adverse

aSymbols used for virus-induced symptoms, Table 3:

0 = Not tested; - = No symptoms; ? = Abnormal plant appearance, nondiscript; (,) = Variable, symptomnot always expressed; * = No back inoculation to test for latent infection; Chl = Chlorosis;ChlS = Chlorotic spots; Ep = Epinasty; t - Latent, localized; LC -O Leaf curl (upward); LL = Locallesions, unspecified, LLc (chlorotic), LLn (necrotic); LR = Leaf roll (downward); Ma = Malformation(distortion, crinkle, savoying, strap leaf, fern leaf); Mo = Mottle or Mosaic; N = Necrosis, general;NS = Necrotic spots (restricted systemic necrosis, zones, spots, flecks); RS = Ring spot, unspecified,RSc (chlorotic), RSn (necrotic); s = Latent, systemic; Str = Streak (stem necrosis, progressive leafnecrosis); Stu = Stunt; VB = Vein banding (chlorotic band on each side of vein); VC = Vein clearing(loss of normal color, chlorosis of vein); VChl = Vein chlorosis; VN = Vein necrosis; W = Wilting.


TABLE 4. Diagnostic key for 38 mechanically transmissible legume viruses.

SECTION I - Viruses inducing symptoms on Vigna unguiculata

V. unguicuiataa -- positiveS. oleracea -- positive

L. esculentum -- positiveG. max, (Bragg) -- positive

G. globosa -- positive b

P. vulgaris (Bountiful) -- local lesions ALFALFA MOSAIC (-, 20 x 60)bP. vulgaris (Bountiful) -- chlorotic spots, systemic mosaic CLOVER BLOTCH (o, 28)

G. globosa -- negative TOBACCO RINGSPOT (o, 28)G. max (Bragg) -- negative

G. globosa -- local lesions PEANUT STUNT (o, 30)G. globosa -- systemic symptoms CUCUMBER MOSAIC (LEGUME STRAIN) (o, 30)

L. esculentum -- negativeN. glutinosa -- positive

C. sativus -- positiveP. vuigaris (Bountiful) -- positive CLOVER (RED) NECROTIC MOSAIC (o, 30)

P. vulgaris (Bountiful) -- negative SOYBEAN MILD MOSAIC (o, 25)C. sativus -- negative BROAD BEAN WILT (o, 25)

N. glutinosa -- negativeP. vulgaris (Pinto 111) -- positive COWPEA APHID-BORNE MOSAIC (- 750)P. vulgaris (Pinto ill)-- negative COWPEA MOSAIC (o, 28)

S. oleracea -- negativeV. faba -- positive

P. hybrida -- positive SOYBEAN MOSAIC (-, 750)P. hybrida -- negative

G. max (Davis) -- positiveC. sativus -- positive CLOVER (WHITE) MOSAIC (-, 480)C. sativus -- negative CLOVER (RED) MOTTLE (o, 30)

G. max (Davis) -- negative PEANUT MOTTLE (-, 750)V. faba -- negative

C. sativus -- positiveP. sativum (DS Perfection) -- positive

G. max (Davis) -- positive TOMATO BLACK RING (o, 30)G. max (Davis) -- negative PEA EARLY BROWNING (z, 105, 215)

P. sativum (DS Perfection) -- negative TOBACCO STREAK (RED NODE) (o, 28)C. sativus -- negative

P. vulgaris (Bountiful) -- positive AZUKI BEAN MOSAIC -750)dP. vuigaris (Bountiful) -- negative COWPEA CHLOROTIC MOTTLE (o, 25)

SECTION II - Viruses inducing no symptoms on Vigna unguiculata

V. unguiculata -- negativeP. vulgaris (Bountiful) -- positive

V. faba -- positiveG. max (Bragg) -- positive

N. tabacum -- positive BEAN YELLOW SEVERE MOSAIC (-, 750)

N. tabacum -- negative BEAN YELLOW MOSAIC (-, 750)G. max (Bragg) -- negative

P. sativum (DS Perfection) -- positive PEA DWARF MOSAIC (o, 25)

P. sativum (DS Perfection) -- negativeM. sativa -- positive CLOVER YELLOW VEIN (-2 750)M. sativa -- negative WISTERIA VEIN MOSAIC (-, 750)

V. faba -- negativeG. mom (Davis) -- positive

P. vulgaris (Pinto 111) -- localized symptomsP. vulgaris (B Turtle) -- localized symptoms BEAN POD MOTTLE (o, 30)P. vulgaris (B Turtle) -- systemic symptoms BEAN SOUTHERN MOSAIC (o, 28)

P. vulgaris (Pinto ill) -- localized and systemic symptoms DESMODIUM YELLOW MOTTLE (o, 30)

G. max (Davis) -- negative BEAN COMMON MOSAIC d,e (-, 750)P. vulgaris (Bountiful) -- negative

P. sativum (DS Perfection) -- positiveP. vulgaris (B Turtle) -- positive

S. oleracea -- positive CLOVER YELLOW MOSAIC (-, 520)S. oleracea -- negative CLOVER (RED) VEIN MOSAIC (--, 645)

P. vulgaris (B Turtle) -- negativeV. faba -- positive

C. amaranticolor -- positive PEA SEEDBORNE MOSAIC (-, 750)C. amaranticolor -- negative PEA STREAKf (-, 620)

V. faba -- negativeC. amaranticolor -- local lesions PEA ENATION MOSAIC (o, 30)C. amaranticoior -- localized and systemic symptoms LETTUCE MOSAIC (-, 750)

P. sativum (DS Perfection) -- negativeC. sativus -- positive

N. glutinosa -- positive SOYBEAN STUNT (o, 30)N. glutinosa -- negative WATERMELON MOSAIC (-, 750)

C. sativus -- negativeD. stramonium -- positive TOMATO SPOTTED WILT (0, 70-90)D. stra•nonium -- negative TURNIP MOSAICd (-, 720)

a Diagnostic plant-host, elaborated in Table 1.

b Particle shape (o = sphere, - = elongated particle), size in nm.

c Clover blotch virus induces variable chlorotic spots in S. olerocea and obscure vein clearing in L. esculentum;

these symptoms may not be dependable under certain greenhouse conditions.d The user of the diagnostic key is encouraged to seek reactive hosts from Table 1, for confirmation of viruses

whose classification is based heavily upon negative host reactions.e Although the Westlandia straLn of bean common mosaic induced symptoms on V. unguiculata, it is assumed that

the majority of BCMV isolates lack this capability.f One of four cooperators indicated that pea streak virus induced symptoms on C. amaranticoZor. Placement of

this virus in the key is based upon non-induction of symptoms in C. damarantiaolor


greenhouse environments on virus-host interactions were the use of this key shall necessarily result in the firmnot accounted for in this study. identification of an unknown virus. Third, differentstrains of the 38 viruses tested in this study are certain toRESULTS AND DISCUSSION induce different symptoms on some of the 23 plant hosts,

The localized and systemic reactions induced by 38 thus posing identification inaccuracies. Fourth, althoughwe attempted to select for use in the key virus-hostvirus isolates on 23 plant hosts, excluding 40 missing interactions resulting in the most conspicuous symptoms,

reactions, are presented in Table 3. Among these virus-hostintracionsthee wre 16 istaces f lcalzed symptom anomalies due particularly to plant nutrition orhost interactions there were 186 instances of localized test environment can be expected. Finally, the user shouldlatent infections and 51 instances of systemic latent recognize that, since the key is based indirectly upon theinfections. Twenty-seven virus-host interactions resulted interactions between viral and plant host nucleic acidsin both localized and systemic latent infection, and is indifferent to other virus properties, very dissimilarAntirrhinum majus L., Trifolium pratense L., and T. viruses with similar virulence on the selected hosts will berepens L. sustained latent infections more frequently thanthe the plat hsts.Desodim yelowmotte vruslocated proximally in the key. Because of this inevitabletheiother plntuced hosts. Docazesodi ayselw mttlent vfeature of the key, a "near miss" in applying the key to anuniquely induced both localized and systemic latent ukonvrspoie itemaigu nomtoinfections in seven of 23 plant hosts inoculated. unknown virus provides little meaningful information

about that virus. Thus, a virus tentatively diagnosed byVariability in symptoms and host range due to virus use of the key should be viewed by electron microscopy toisolate differences was appraised by comparing host determine whether or not its particle morphologyreactions induced by three isolates for each of five viruses. atches that of the virus indicated by the key. ShouldAgreement of results obtained for isolates by the particle morphology match the virus in the key, finalinvestigators was substantial. Minor disagreements were identification should be confirmed by serology, and,noted and hosts emphasizing isolate differences were where possible, by other properties of the virus particles.avoided in formulating the key. Significant deviations inisolate character are footnoted in Table 4.

From these data, a key (Table 4) was constructed aftersuccessively evaluating various arrangements of selectedplant hosts and hierarchies of these hosts. In accord with LITERATURE CITEDthe premises previously discussed, a key was formulatedwhich placed major emphasis on the responses to 38 1. BOS, L. 1964. Tentative list of viruses reported fromviruses by Vigna unguiculata, Spinacea oleracea, naturally infected leguminous plants. Neth. J. PlantPhaseolus vulgaris, Lycopersicon esculentum, Viciafaba, 2. BOS, L., D. J. HAGEDORN, and L. QUANTZ. 1960.and Pisum sativum. Fourth- through seventh-order Suggested procedures for international identification ofsubdivisions in the keys were facilitated by the reactions legume viruses. Tidschr. Plantenziekten 66:328-343.to viruses by 12 additional plant hosts. 3. BOS, L., and J. P. H. VAN DER WANT. 1958. VirusDichotomous choices, preferred for toxonomic keys, diseases of leguminous plants. Landbouwvoorlichtingwere constructed in all possible cases, based upon 15:550-558, 573-587.whether (positive) or not (negative) viruses induced 4. GIBBS, A. J., B. D. HARRISON, and A. F. MURANTobvious symptoms on key hosts. When this was not (eds.). 1970-1976. Descriptions of plant viruses, Nos. 1-possible because of identical host ranges among viruses, 170. Commonwealth Mycological Institute and thedifferentiation was achieved by qualitative Association of Applied Biologists, Kew, Surrey, England.symptomatology. 5. HAGEDORN, D. J. 1974. Diagnosis of pea viruses. Pages15-19 in Virus diseases of pea, Pisum sativum.Coincident with our final choice of plant hosts and Phytopathol. Monogr. 9, Am. Phytopathol. Soc., St.hierarchical arrangement of these hosts for the key, Paul, Minnesota. 47 p.several viruses tended to be grouped together according 6. JAMES, E. 1972. The organization of the National Seedto natural host relationships. For instance, four of the Storage Laboratory. Pages 397-404 (Appendix No. I) in"clover viruses" were virulent to V. unguiculata, whereas Viability of Seed. Chapman and Hall, Ltd., London. 410the five "bean viruses" lacked virulence to this host. P-Similarly, three "pea viruses" were virulent to P. sativum 7. SEEDBANK SUBCOMMITTEE, COMMITTEE ONand V.faba, but lacked virulence to V. unguiculata and P. VIROLOGY, AMERICAN PHYTOPATHOLOGICALvulgaris. SOCIETY. 1977. Virus indicator species available.Phytopathol. News 11:26.

Although we have pursued the ideal of developing a 8. STEWART, V. B., and D. REDDICK. 1917. Bean mosaic.definitive key to aid in diagnosing legume viruses, we have Phytopathology 7:61 (Abstr.).recognized several substantive limitations. Several 9. VANDERVEKEN, J. J. F. 1976. International Workingqualifications are therefore appropriate. First, because Group on Legume Viruses Report of the 'host range'negative ractions were employed as a virus-host reaction committee. Parasitica 32:58-62.category in the key, and because reliance upon negative 10. VAN DER WANT, J. P. H., M. L. BOERJIAN, and D.reactions accumulates as the user progresses through the PETERS. 1975. Variability of some plant species fromkey, confirmations of certain virus identities are different origins and their suitability for virus work. Neth.dependent upon virus-host reactions from Table 3 which J. Plant Pathol. 81:205-216.dresplenental uon virusthe reactons fereomgTabe 3twcha 11. WEISS, F. 1939. A key to the typical viruses of leguminousare supplemental to the key. Second, we recognize that crops. Plant Dis. Rep. 23:352-361.numerous viruses will be discovered which are distinct 12. WEISS, F. 1945. Viruses described primarily on leguminousfrom those included in this study; this, indeed, is one of vegetable and forage crops. Plant Dis. Rep. Suppl.the purposes of the key. We, therefore, do not imply that 154:32-80.

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