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How to deal with complex virus disease problems
The document discusses the impact of tospovirus diseases, particularly affecting vegetables, and highlights the role of thrips as vectors in spreading these viruses. It outlines various thrips species involved in transmission, their ecological adaptability, and the challenges posed in managing these diseases due to the complexity of the virus and vector interactions. Additionally, the document emphasizes the need for integrated pest management strategies to minimize crop losses in affected regions.
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How to deal with complex virus disease problems
- 1. Dealing with complexvirus disease problems a case of Tospovirus Diseases in Vegetables Naidu A. Rayapati Department of Plant Pathology Washington State University Irrigated Agriculture Research & Extension Center Prosser, WA 99350, USA naidu@wsu.edu
- 2. Topics An overview Thripsvectors Tospoviruses
- 3. Thrips: What arethey? Thrips : Greek word for “wood worms” Thrips : a plural noun Each individual is “a thrips” like the word “sheep”
- 4. What are Tospoviruses? Type member: Tomato spotted wilt virus Group of emerging plant viruses causing economically significant damage to a broad range of field crops, vegetables, ornamentals, fruits, etc.
- 5. Thrips play avital role in the spread of tospoviruses The virus disease triangle Tospovirus • Viruses can not move by themselves • They need a “safe” vehicle to spread from plant to plant Thrips • Thrips control strategies Host may be a better option to disrupt the disease triangle
- 6. Thrips as vectorsof viruses • As vectors directly transmitting viruses e.g. Tospoviruses in vegetables, field crops and ornamentals • As carriers of pollen containing viruses e.g. certain other viruses (Tobacco streak virus)
- 7. General features ofthrips • Small size - difficult to detect • Polyphagous - feed on a broad range of plant species - feed on different parts of the plant (pollen, flower structures, leaves, stems) • Show habitat infidelity - extraordinary ability to adapt - can expand geographic range - can spread to new crops • Have superior reproductive output - produce many off springs • Have propensity to ‘overwinter’ on a broad range of plant species - survive through out the year Source: Zenkoko Noson, • Vectors of viruses Kyoiku Kyoiku Co. Ltd, Japan. - Spread virus diseases
- 8. Thrips • Approximately 5500species of thrips described • About 40% known to feed on higher plants • The rest exploits lower plant families (gymnosperms, ferns and fungi) • Some species are predatory
- 9. Thrips species implicatedin tospovirus transmission • 12 species in 4 genera • About 0.16% (12/5500) of the known Thysanoptera Order: Thysanoptera Family: Thripidae
- 10. Thrips species implicatedin tospovirus transmission Thrips palmi Frankliniella occidentalis T. tabaci F. fusca T. setosus F. bispinosa Scirtothrips dorsalis F. schultzei Ceratothrips claratris F. intosa F. zucchini 12 F. schultzei species
- 11. Thrips species implicatedin tospovirus transmission Frankliniella occidentalis* Thrips tabaci* F. fusca* T. palmi* F. bispinosa* T. setosus F. schultzei Scirtothrips dorsalis F. intosa Ceratothrips claratris F. zucchini F. schultzei *Major vectors in the USA *Present in the US, but vectoring capacity not clear
- 12. Major vector thripsin the USA • F. occidentalis (Western flower thrips) Polyphagous (many fruits, vegetables, ornamentals, seed crops, cotton) Throughout USA • F. fusca (Tobacco thrips) Polyphagous (common in grasslands, peanut, tobacco, cotton) South & Southeastern USA • T. tabaci (Onion thrips) Polyphagous (onion, cabbage, tobacco, cotton, vegetables and ornamentals) Throughout USA
- 13. Thrips species implicatedin tospovirus transmission Thrips palmi* Frankliniella occidentalis** T. tabaci* F. fusca T. setosus F. bispinosa Scirtothrips dorsalis* F. schultzei* Ceratothrips claratris* F. intosa F. zucchini F. schultzei *Present in Asia-Pacific Region **Present in some countries of Asia-Pacific Region
- 14. List of characterizedtospoviruses TSWV = Tomato spotted wilt virus GRSV = Groundnut ringspot virus TCSV = Tomato chlorotic spot virus CSMV = Chrysanthemum stem necrosis virus ZLCV = Zucchini lethal chlorosis virus INSV = Impatiens necrotic spot virus PBNV = Peanut bud necrosis virus WSMV = Watermelon silver mottle virus WBNV = Watermelon bud necrosis virus CaCV = Capsicum chlorosis virus MYSV = Melon yellow spot virus IYSV = Iris yellow spot virus As of 2007 TYRV = Tomato yellow fruit ring virus PYSV = Peanut yellow spot virus 16 PCFV = Peanut chlorotic fanspot virus CCSV = Calla lily chhlrotic spot virus
- 15. Tospoviruses – aglobal view 92 TCSV 17 96 GRSV 6 viruses viruses 100 TSWV distributed primarily 100 CSNV 90 ZLCV in Americas INSV 100 TYRV IYSV MYSV 100 100 TZSV 100 CCSV 11 viruses 74 CaCV WSMoV distributed primarily 100 71 WBNV in Eurasia 63 GBNV GCFSV 100 GYSV 0.1 Some exceptions TSWV - in Europe, Africa, Australia & Japan IYSV - in the Americas and Australia
- 16. Geographic structuring oftospoviruses within South & Southeast Asia S. Asia Southeast PBNV Asia WBNV CaCV PYSV WSMV IYSV MYSV PCFV
- 17. Thrips species implicatedin tospovirus transmission Thrips palmi Frankliniella occidentalis T. tabaci F. fusca T. setosus F. bispinosa Scirtothrips dorsalis F. schultzei Ceratothrips claratris F. intosa F. zucchini 12 F. schultzei species
- 18. Association between tospovirusesand thrips vectors 92 TCSV 96 GRSV Group 1 100 TSWV Primary vector CSNV 100 Frankliniella sp. 90 ZLCV INSV 100 TYRV IYSV MYSV 100 100 TZSV Group 2 100 CCSV Primary vector 74 CaCV Thrips sp. 100 WSMoV 71 WBNV 63 GBNV GCFSV Group 3 100 GYSV Primary vector Scritothrips sp. 0.1 Phylogenetic tree - N protein
- 19. Peanut bud necrosisvirus a threat to tomato sustainability in India
- 20. Peanut bud necrosisvirus (PBNV) a major threat to tomato sustainability in India
- 21. Peanut bud necrosisvirus a threat to tomato sustainability in India Healthy Infected
- 22. Peanut bud necrosisvirus • affects quality and shelf life • loss of income
- 23. Capsicum chlorosis virusin South Asia Symptoms mimic those produced by PBNV
- 24. Life stages ofthrips Larva II ♂ ♀ Prepupa Larva I Adult Adult Pupa Egg Western Flower Thrips Ullman et. al., 1997 • Larvae and adults: feeding stages • Pre-pupa and pupa: non-feeding stages • Gender can not be determined until adult state • Larva - adult = 15-20 days
- 25. Interdependency between vectorlife-stage and productive virus transmission Virus Symptom I instar st acquisition by larva is crucial expression larva Unique among plant viruses II nd instar Adult larva Only adults that acquire virus as larva can transmit Prepupa Quiescent Virus replicates & Pupa & passage occurs from Ullman et. al., 1997 Do not feed one stage to the other
- 26. Tospoviruses Tomato Peanut • A serious threat to vegetables, ornamentals, food and cash crops • ~1000 species of plants in about 70 plant families (dicots & monocots) Pepper Onion • an estimated global yield Tobacco losses of up to $1 billion Ornamentals Potato
- 27. Tospoviruses multiply intwo disparate hosts Thrips vector Plants Female Male Thrips not a vector but a mobile host
- 28. Gender-specific differences in virus transmission Western flower thrips Male Female Transmission efficiency Male 46% Female 12% Males are efficient transmitters
- 29. Tospoviruses have acomplex structure SDS-PAGE of Electron micrograph TSWV particle proteins of TSWV particles Drawing of TSWV particle TSWV Mr kDa Replicase 150 GC 100 75 S M GN 50 L 35 N 25 15 Pleomorphic particles = 80-120 nm size
- 30. Tospoviruses have acomplex genome Organization Replicase L-RNA 8.9 kb NSm GN/GC N GC Replicase M-RNA 4.8 kb GN NSs N S-RNA 2.9 kb L-RNA = negative sense M- & S- RNA = Ambisense • Tri-partite genome: three genomic segments • Hybrid particles: virus-encoded and host-derived
- 31. A tospovirus canbe transmitted by more than one thrips vector Virus Thrips vector Tomato spotted wilt virus Frankliniella occidentalis F. fusca F. intosa F. bispinosa F. schultzei Thrips tabaci T. setosus Impatiens necrotic spot virus F. occidentalis F. fusca F. intosa F. schultzei
- 32. A single speciesof thrips vector can transmit more than one tospovirus Thrips vector Virus F. occidentalis Tomato spotted wilt virus Impatiens necrotic spot virus Tomato chlorotic spot virus Groundnut ringspotvirus Chrysanthemum stem necrosis virus T. palmi Peanut bud necrosis virus Watermelon silver mottle virus Watermelon bud necrosis virus Melon yellow spot virus Capsicum chlorosis virus Tomato spotted wilt virus ??
- 33. Geographic expansion ofthrips vectors Western flower thrips (WFT) (Frankliniella occidentalis) • A native to the southwestern USA • Spread through global trade in ornamental greenhouse plants around the world from mid-1980s Melon thrips (Thrips palmi) • A native to Southeast Asia • Expanded its geographic range in 1970s and 80s Source: www.eppo.org
- 34. Viruses and insects do not carry passports • virus vectors introduced Global village in to new areas • viruses introduced in to new areas by land, sea and air, via international trade or accidentally The planetary ecosystem has changed !!!
- 35. Challenges in controlling tospovirus diseases Tospoviruses • broad host range • multiple vector species • evolution of new strains • ability to overcome host plant resistance
- 36. Challenges in controlling tospovirus diseases Vector thrips • polyphagous & show habitat infidelity • has superior reproductive output • has propensity to ‘overwinter’ on a broad range of plant species • develop resistance against pesticides
- 37. Challenges in controlling tospovirus diseases Host plant resistance Resistance only against TSWV • Sw-5 resistance gene in tomato against TSWV • Tsw resistance gene in Capsicum against TSWV
- 38. Challenges in controlling tospovirus diseases Host plant resistance • No broad-spectrum resistance e.g. CaCV overcame the Sw-5 resistance gene in tomato e.g CaCV overcame TSWV resistance in Capsicum chinense accessions PI 152225, PI 159236 and AVRDC 00943 • Resistance to ‘Asian’ tospoviruses not yet known e.g. is there resistance to PBNV in tomato ?
- 39. Challenges in controlling tospovirus diseases Host plant resistance • virus-specific • no ‘one-size-fits all’ approach
- 40. Durable resistance isdifficult to achieve due to rapid evolution of resistance-breaking virus strains K.S. Ravi, Mahyco, India
- 41. Crop Improvement against tospoviruses biologic chess game !!!
- 42. Management of tospovirus diseases: an IPM approach • Knowledge about the virus & vector • Diagnostic tools • Ecology and epidemiology • Thrips vector management options • Altering cropping patterns • Deploying tolerant/resistant cultivars • Capacity building
- 43. Integrated Management ofThrips-borne Tospoviruses in Vegetable Cropping Systems in South Asia and Southeast Asia Region Funded by Integrated Pest Management Collaborative Research Support Program (IPM CRSP) of USAID Global IPM Theme: Insect-transmitted viruses
- 44. Project Goal “minimize croplosses due to thrips-borne tospoviruses in smallholder vegetable farming systems in South and Southeast Asia through new science and technologies and multidisciplinary global partnerships, and improve nutritional status of people including women and children”
- 45. Project Objectives 1. Conductstrategic research on tospoviruses and thrips vectors 2. Carryout applied and adaptive research to deploy ‘eco-friendly’ IPM strategies to control tospovirus diseases 3. Strengthening institutional capacities within host countries to conduct problem-oriented research on virus diseases (short- and long-term training)
- 46.
Editor's Notes
- #25 Thrips have different developmental stages