FACEBOOK/Agriculture Delhi www.facebook.com/AgricultureDelhi Somesh Jha, M.Sc.(Agri.) Plant Pathology is a Delhi based Freelance Agroconsultant who has been active in the sector of Agro, Retail and Agri Business consultancy for more than 17 years and has also served companies like Vishal Retail, Reliance Retail, Aadhaar Retailing(Future Group),Godrej Agrovet Ltd., Pragya (NGO) at various managerial levels. Carried out Capacity Building training programs for a reputed agri input company. Skills training of sales team in paddy and wheat belt such as Sangrur, Bathinda, Hanumangarh, Jaipur and Jodhpur. Carried out Behavioral Training program as a Freelance Trainer with a NSDC partner company, for one of the reputed hybrid seed company. Skills training of sales team in cotton belt of Punjab and Haryana regions

3. SEED INFECTION AND TRANSMISSION OF
PLANT VIRUSES
Speaker : Somesh Jha
Advisor: Dr. B. N.
Patel
Date: 13th July,2001

4. t r an sm ission of p lan t
vir u ses
Introduction
Economic importance and significance
Seed
Seed infection
W all plant viruses are not seed transmitted?
hy
Types of viruses that are seed transmitted
Seed health research activities
Conclusion

5. INTRODUCTION

6. Introduction
Seed - B asic input resource
Virus transmission through seed -
H ighly significant in virus preservation
and spread.
Seed transmissible viruses - adverse
effect on seed and crop health
18% of known plant viruses are seed
transmitted

7. SYM T S ON P
P OM ODS AND SE DS OF COW E
E PA

8. Economic importancE
and
significancE

9. E con om ic im p . &
sig n ifican ce
Direct loss Barrier to
to seed & crop world trade
Epidemiological Seed transmission Introduction in
of
significance new area
viruses
Ecological significance
Perpetuation Perennation Dissemination

10. S P
YM TOM OFUL
S CV

11. SOME IMPORTANT SEED BORNE VIRUSES
Alfa- alfa mosaic Medicago sativa
Barley stripe mosaic Hordeum vulgare
Triticum aestivum
Bean common mosaic Phaseolus vulgaris
Vigna unguiculata
Bean southern mosaic P. vulgaris
Brinjal mosaic Solanum melongena

12. SYMPTOM OF CABMV ON COWPEA

13. Contd…
Citrus mosaic Citrus sinensis
Cowpea mild mottle V. unguiculata
Glycine max
Cucumber green mottle mosaic Cucumis sativus
Lagenaria siceraria
Maize dwarf mosaic Zea mays
Pea seed borne mosaic Pisum sativum
Peanut clump Arachis hypogaea
Potato X S. tuberosum

14. ULCV ON COWPEA
SYMPTOM

15. Contd…
Soyabean mosaic G. max
Tobacco etch Nicotiana tabacum
Tobacco ring spot N. glutinosa
Urdbean leaf crinkle P. aureus
Wheat streak mosaic Zea mays

16. ULCV ON MUNGBEAN
S
Y
M
P
T
O
M
S

18. S eed
Seed
st r u ctu r e
A fragile, living organism – a miracle of life
corn (monocot seed)

19. S eed
st r u ctu r e
Bean (Dicot seed)

21. Seed infection
VIRUS CARRIED ON THE SURFACE OF SEEDS
e.g. TMV Remains viable as contaminant
Seedling infection
Mechanical transmission during handling

22. 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 and
embryo Seed transmission
Reddy et al.,
(1998)

23. S eed
F or m ation

24. EMBRYO INFECTION
Three Ways
Through introduction of virus into the embryo sac by
the male gametophyte
Germination Pollen tube grows
Infected pollen grain into Embryo Sac
Release
male gametes Union
ctede with
Infe met (if infected) polar
Infected Union with ga nuclei
embryo egg cell
Infected Endosperm
e.g. Tobacco Rattle Virus (TRV) & Alfa-alfa Mosaic Virus (AMV)

25. SYMPTOMS

26. Through ovule invasion by virus from the
mother plant
Adjacent cells
Virus Developing
of mother Infected
ovule in early
plant ovule
stage
(Infected)
e.g. Soybean Mosaic Potyvirus (SMV) route of Soybean
embryo infection by invasion of the ovules
Dong Hong Ping et al., (1997)

27. COLOUR DISCOLOURATION DUE TO SMV
SOYBEAN SEEDS

28. Through direct invasion of the
embryo
Inoculation Infected
after embryo
flowering
e.g. PSbMV
Location Testa, Cotyledons Transmission Embryonic axis
BCMV & Embryonic
in bean & Cotyledons
axis
Bravo and Pineda (1996)

30. Why all plant virusEs arE
not sEEd transmittEd ?
Factors preventing virus passage
through seed to the next generation
Inactivation of virus in the embryo Medium
Embryo High energy Low Unfavorable
Phosphates Conc
No virus increase
Sterility of infected gametes
Direct Gametes or Infected seeds
Virus lethal effects prevented
embryo

31. Inability of virus to infect young embryo
Embryo
Virus restricted to No embryo
No vascular connection infection
Vascular System
Mother plant
Protection of the embryo from virus infection
Interposition of No movement of
structures between Embryo escapes
the mother plant infection
virus
& embryo

32. 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)

33. Types of viruses that
are seed transmitted

34. Types of viruses that are
seed transmitted
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)

35. Contd…
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 Virions/ Developing
suspensor embryo
maternal tissue Viral RNA

36. Contd..
Cross-communicative interaction between
nuceller/
integument cells & the endosperm and between the
endosperm & interfacing embryo cells during
embryogenesis.
Integument
VIRUS PASSAGE Endosperm
transfer cells
Cellular/biochemical factors interacting with virions or viral RNA
Embryo
invasion
Interactive signal
Viral Host-plant
genome genome

37. Rate of seed transmission of some
plant viruses
Chickpea 0.1-1.0 % 0.1-2.0 % Jones and Coutts (1995)
AMV CMV
Lentil 0.1-5.0 % 0.1-2.0 % Australia
Soybean 12.6 % (mild mosaic sym.) SMVKim Yul Ho et al., (1997)
14.1 % (severe mos. sym.) Korea Republic
Mung bean 2.0-16.0 % Mahajan and Joi (1999)
ULCV
Urd bean 1.16-11.0% Rahuri, India
Pea 1.9-32.7 % (PSbMV) Gallo and Jurik (1995)
(Diff. Cult.) Slovak Republic
Tomato 1.0-17.0 % (ToMV)
Chitra et al., (1999)
Bell Pepper 1.0-10.0 % (TMV) India

38. Contd..
Physalis minima 1.17 % Rajkumar and Jitender
Solanum nigrum 2.20 % LMV Mohan (1994), U.P.,
Nicotiana plumbaginifolia 4.70 %
India
Cowpea 7.0-32.0 % 1.0-4.7% 1.0-3.0 % Nain et al., (1994)
(V. unguiculata) BLCMV CPMV CPMMV Hissar, India
Cowpea 3.0-25.0 % SBMV Makwana et al., (2000)
Cowpea 10.0-30.0% CAbMV Sheela et al., (2001)
Anand, India

40. Seed health research activities
Several IARCs in the CGIAR system are working
ICARDA Effect of dry heat on lentil seeds
70° C
Heat treatment BBSV eliminated
Further plans with PSbMV and BYMV
CIP On PVT in true seeds
Reports
HW
Soybean SMV eliminated Ghufran-ul-Haque et al., (1993)
seeds 70° C Pakistan
DH
L. siceraria CGMMV K.D. Hyun and Lee. J. Myung
75° C, 3 days
seeds inactivated (2000), Korea Republic

42. conclusion
Seed infection & transmission is related to host-pathogen
interactions. Only a minority of these interactions resulting in
infection also result in seed transmission
Even low rates of seed transmission in conjunction with secondary
spread 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.