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Plant Virology

Plant Virology. The 30 minute semester with 3 examples from MT. PVY. WSMV. BYDV. Diagnosis. Symptoms Mechanical or insect transmission Immunological (ELISA) Nucleic acid (PCR). How do viruses move from plant to plant?. Insect vectors, nematodes

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Plant Virology

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  1. Plant Virology The 30 minute semester with 3 examples from MT PVY WSMV BYDV

  2. Diagnosis • Symptoms • Mechanical or insect transmission • Immunological (ELISA) • Nucleic acid (PCR)

  3. How do viruses move from plant to plant? • Insect vectors, nematodes • Mechanically (sap on clothing/tools/equipment) • Seed, tubers • Pollen

  4. Host Vector Pathogen Environment Virus diseases in MT • Occur sporadically • Difficult to predict • Potato virus Y • Wheat streak mosaic virus • Barley yellow dwarf virus

  5. Insect transmission of plant viruses: The Jargon • Vector = insect (or other means) of transmitting the virus from plant to plant • Nonpersistant (stylet-borne) • Semipersistant • Persistant • Circulative, propogative • Circulative, nonpropogative

  6. Insect transmission of plant viruses: The Jargon, cont’d

  7. Control of nonpersistant vs. persistant • Insecticides are effective against persistant, but not nonpersistant viruses • Plant resistance can be effective, but viruses evolve rapidly • Prevent introducing the virus inoculum (seed, tubers) • Prevent movement from volunteer plants by getting rid of volunteers before planting (green bridge)

  8. Potato virus Y (PVY): The Host • Solanum tuberosum (potato) • Capsicum spp. (peppers) • Nicotiana spp. (tobacco) • Lycopersicon esculentum (tomato) Primary source of inoculum = Seed potatoes

  9. 125I-TEV Potato virus Y (PVY): The Pathogen • Potyvirus (40% all known plant viruses) • Nonpersistant (stylet-borne) • Aphid transmitted

  10. X Nonpersistant viruses stick to the stylet Mediated by a protein, HC-Pro Specific relationship

  11. PVY: The Environment (control) • PVY does not spread rapidly in the absence of the aphid vector • Can be transmitted mechanically • Insecticides are not effective • Best option is preventing inoculum introduction • Some variety resistance

  12. Host Vector Pathogen Environment PVY: Disease triangle : Resistance : Avoidance : Exclusion – certified seed : Scouting : Roguing

  13. Wheat streak mosaic virus: The Host • Infects both winter and spring wheat • Symptoms in spring • Earlier infection = greater yield loss • Grassy weeds, volunteer wheat, corn, etc. can harbor both WSMV and the mite vector

  14. WSMV: The Pathogen • Family Potyviridae, genus Rymovirus • Mite-transmitted virus • Wheat curl mite survives on green tissue

  15. WSMV: The Environment • Warm, dry conditions favor mite reproduction

  16. X Wheat streak mosaic virus control • Early seeding of winter wheat favors mite and WSMV spread • Eliminate the green bridge • 3 week gap between herbicide and planting • Avoid spraying herbicide on volunteer wheat near spring wheat fields during cool, moist, windy weather • Do not plant wheat next to late-maturing (green) corn, which is also a mite host

  17. Disease cycle of WSMV

  18. Role of the predominant grassy weeds as reservoirs of WSMV

  19. Weed Host: Volunteer Wheat

  20. Host Vector X Pathogen Environment WSMV: Disease triangle : Resistance : Avoidance : Seed transmission (don’t use seed from heavily infected plants) :be aware of the weather

  21. Barley yellow dwarf virus: The Host • Infects barley, wheat, oats, rye, corn, triticale, rice • Resistance has been developed, but predicting the virus and aphid populations from year to year can be difficult

  22. BYDV: The Pathogen • Family Luteoviridae • Persistant, circulative, nonpropagative • First classified by primary aphid vector MAV: Macrosiphum (Sitobion) avenae PAV: Rhopalosiphum padi RMV: Rhopalosiphum maidis SGV: Schizaphis graminum RPV: Rhopalosiphum padi

  23. Insect transmission of plant viruses

  24. Circulative – nonpropagative (Another very specific relationship) Food Salivary Canal Canal Hemocoel ASG PSG Midgut Hindgut Phloem

  25. BYDV: The environment • Inoculum • Wild grasses, perennial grassy weeds • Aphid flights from other wheat-growing areas • Insecticides can be very effective at controlling the aphid and virus transmission, if applied early

  26. Host Vector Pathogen Environment BYDV: Disease triangle : Resistance : Insecticide : Control grassy weeds : Scouting

  27. Wheat streak mosaic virus: The Host • Infects both winter and spring wheat • Symptoms in spring • Earlier infection = greater yield loss • Grassy weeds, volunteer wheat, corn, etc. can harbor both WSMV and the mite vector

  28. WSMV: The Pathogen • Family Potyviridae, genus Rymovirus • Mite-transmitted virus • Wheat curl mite survives on green tissue

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