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8/6/2019 Seed Borne Threats presented by Somesh Jha,M.Sc.(Agri.) during Thesis Seminar 2001
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8/6/2019 Seed Borne Threats presented by Somesh Jha,M.Sc.(Agri.) during Thesis Seminar 2001
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SEED INFECTION AND TRANSMISSION OF
PLANT VIRUSES
Speaker : Somesh Jha
Guide: Dr. B. N. Patel
Date: 13th
July,2001
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Seed infection and transmission
of plant virusesIntroduction
Economic importance and significance
Seed
Seed infection
Why all plant viruses are not seed transmitted?
Types of viruses that are seed transmittedSeed health research activities
Conclusion
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INTRODUCTION
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IntroductionSeed - Basic input resource
Virus transmission through seed - Highly
significant in virus preservation andspread.
Seed transmissible viruses - adverse effect
on seed and crop health18% of known plant viruses are seedtransmitted
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SYMPTOMS ON PODS AND SEEDS OF COWPEA
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ECONOMIC IMPORTANCEAND
SIGNIFICANCE
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Seed transmissionof
viruses
Epidemiological
significance
Introduction in
new area
Ecological significance
Perpetuation Perennation Dissemination
Barrier to
world tradeDirect loss
to seed & crop
Economic imp. &
significance
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SYMPTOMS OF ULCV
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SOME IMPORTANT SEED BORNE VIRUSES
AlfaAlfa-- alfa mosaicalfa mosaic Medicago sativaMedicago sativa
Barley stripe mosaicBarley stripe mosaic Hordeum vulgareHordeum vulgare
Triticum aestivumTriticum aestivum
Bean common mosaicBean common mosaic Phaseolus vulgarisPhaseolus vulgaris
Vigna unguiculataVigna unguiculata
Bean southern mosaicBean southern mosaic P. vulgarisP. vulgaris
Brinjal mosaicBrinjal mosaic Solanum melongenaSolanum melongena
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SYMPTOM OF CABMV ON COWPEA
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Citrus mosaic Citrus sinensis
Cowpea mild mottle V. unguiculata
Glycine max
Cucumber green mottle mosaic Cucumis sativus
Lagenaria siceraria
Maize dwarf mosaic Zea maysPea seed borne mosaic Pisum sativum
Peanut clump Arachis hypogaea
Potato X S. tuberosum
Contd
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ULCV ON COWPEA
SYMPTOM
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Soyabean mosaic G. max
Tobacco etch Nicotiana tabacum
Tobacco ring spot N. glutinosa
Urdbean leaf crinkle P. aureus
Wheat streak mosaic Zea mays
Contd
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ULCV ON MUNGBEAN
S
Y
MPT
O
MS
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corn
Seed structure
Seed A fragile, living organism a miracle of life
(monocot seed)
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Seed structure
Bean (Dicot seed)
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Seed infection
VIRUS CARRIED ON THE SURFACE OF SEEDS
e.g. TMV Remains viable as contaminant
Seedling infection
Mechanical transmission during handling
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VIRUS CARRIED IN PARTS OF SEED
OUTSIDE THE EMBRYO
BYMV & CMV Testa & Endosperm
Sugarbeet Curly Top Virus Perisperm
Very few of such viruses result in seed transmission
Southern bean Mosaic Sobemovirus
IPCV Virus present only in cotyledons andembryo Seed transmission
Reddy et al., (1998)
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Seed Formation
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EMBRYO INFECTION
Three WaysThrough introduction of virus into the embryo sac by the
male gametophyte
Infected pollen grainGermination Pollen tube grows
into Embryo SacRelease
male gametes
Union with
egg cell
Infected
embryo
(if infected)
Union
with
polar
nuclei
Infected Endosperm
e.g. Tobacco Rattle Virus (TRV) & Alfa-alfa Mosaic Virus (AMV)
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SYMPTOMS
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Through ovule invasion by virus from the mother
plant
Adjacent cells
of mother
plant
(Infected)
Virus Developing
ovule in earlystage
Infected
ovule
e.g. Soybean Mosaic Potyvirus (SMV) route of Soybean
embryo infection by invasion of the ovulesDong Hong Ping et al., (1997)
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COLOUR DISCOLOURATION DUE TO SMV
SOYBEAN SEEDS
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Through direct invasion of the embryo
Inoculation
after flowering
Infected
embryo
e.g. PSbMV
Testa, Cotyledons Embryonic axis
& Cotyledons
Location & Embryonic
axis
TransmissionBCMVin bean
Bravo and Pineda (1996)
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WHY ALL PLANT VIRUSES ARE
NOT SEED TRANSMITTED ?
Factors preventing virus passagethrough seed to the next generation
Inactivation of virus in the embryo
Embryo High energyPhosphates Conc
Medium
Unfavorable
No virus increase
Sterility of infected gametes
VirusDirect
lethal effectsGametes or
embryo
Infected seeds
prevented
Low
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Inability of virus to infect young embryo
Virus restricted to
Vascular System
Embryo
Mother plant
No vascular connectionNo embryo
infection
Protection of the embryo from virus infection
Interposition of
structures between
the mother plant
& embryo
Embryo escapes
infection
No movement of
virus
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Other factors
Environmental factors
Host plant and virus
Nematode trans. Virus Seed trans.
e.g. tomato black ring virus
Listler and Murant (1967)
Longevity of Virus in seed
Varies one month (Dodder Latent Mosaic)
to >six years (Barley Stripe Mosaic)
Scott (1961)
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Types of viruses that
are seed transmitted
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Typesof virusesthat areseed
transm
itted
Certain general characteristics
Most are readily sap transmissible
Transmitted by certain types of vectors
e.g. Several non-persistent aphid transmitted viruses
Nematode transmitted viruses
Listler and Murant (1967)
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Three points of plant reproduction which
extrapolate virus trans. through seeds
A relatively long term conductive (embryo-supportive)function is ascribed to the developing suspensor
Infected
maternal tissue
Virions/
Viral RNA
suspensorDeveloping
embryo
Contd
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Cross-communicative interaction between
nuceller/integument cells & the endosperm and between
the endosperm & interfacing embryo cells duringembryogenesis.
Integument
transfer cellsEndosperm
Cellular/biochemical factors interacting with virions or viral RNA
Viral
genome
Interactive signal
Embryoinvasion
Host-plant
genome
VIRUS PASSAGE
Contd..
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Rate of seed transmission of some plant viruses
Chickpea 0.1-1.0 % 0.1-2.0 %
Lentil 0.1-5.0 % 0.1-2.0 %AMV CMV
Jones and Coutts (1995)
Australia
Soybean 12.6 % (mild mosaic sym.) KimY
ul Ho et al., (1997)Korea Republic
Mung bean 2.0-16.0 %
Urd bean 1.16-11.0%ULCV
Mahajan and Joi (1999)
Rahuri, India
14.1 % (severe mos. sym.)SMV
Pea 1.9-32.7 % (PSbMV) Gallo and Jurik (1995)
SlovakRepublic
Tomato 1.0-17.0 % (ToMV)
(Diff. Cult.)
Bell Pepper 1.0-10.0 % (TMV) Chitra et al., (1999)India
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Physalis minima 1.17 %Solanum nigrum 2.20 %Nicotiana plumbaginifolia 4.70 %
LMVRajkumar and Jitender
Mohan (1994), U.P.,
India
Cowpea 7.0-32.0 % 1.0-4.7% 1.0-3.0 %(V. unguiculata) BLCMV CPMV CPMMV
Nain et al., (1994)Hissar, India
Cowpea 3.0-25.0 % SBMV
Cowpea 10.0-30.0% CAbMV
Makwana et al., (2000)
Sheela et al., (2001)
Anand, India
Contd..
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Seed health research activities
Several IARCs in the CGIAR system are workingICARDA Effect of dry heat on lentil seeds
Heat treatment BBSV eliminated
Further plans with PSbMV and BYMV
CIP On PVT in true seeds
Reports
Soybean SMV eliminated Ghufran-ul-Haque et al., (1993)Pakistanseeds
L. siceraria CGMMV K.D. Hyun and Lee. J. Myung
seeds inactivated (2000), Korea Republic
70 C
HW70 C
DH
75 C, 3 days
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conclusion
Seed infection & transmission is related to host-pathogeninteractions. Only a minority of these interactions resulting ininfection also result in seed transmission
Even low rates of seed transmission in conjunction with secondaryspread by insect vectors can result in the introduction of viruses into
new area and can produce viral disease epidemics
Cytoplasmic connections between the mother plant and flower and
then developing seeds may influence the seed infection
In terms of world trade, seed-borne viruses act as barrier. Hence,
detection of seed-borne viruses has to play an important role in
quarantine.
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