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Plant Disease threats for 2009 Wheat viruses Stem rust

Plant Disease threats for 2009 Wheat viruses Stem rust. Dr. Mary Burrows Montana State University, Bozeman, MT. WSMV: The Pathogen. Family Potyviridae , genus Tritimovirus Mite-transmitted virus. SDSU Extension. Wheat streak mosaic virus. Infects both winter and spring wheat

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Plant Disease threats for 2009 Wheat viruses Stem rust

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  1. Plant Disease threats for 2009Wheat virusesStem rust Dr. Mary Burrows Montana State University, Bozeman, MT

  2. WSMV: The Pathogen • Family Potyviridae, genus Tritimovirus • Mite-transmitted virus

  3. SDSU Extension Wheat streak mosaic virus • 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 • 5-10% yield loss/yr across Great Plains • 100% yield loss in individual fields

  4. No chemical controls are effective for control of mite or virus

  5. The life cycle of mite-transmitted wheat viruses

  6. Weed Host: Volunteer Wheat

  7. WSMV in Montana weeds Volunteer wheat is the best non-crop host, but weed species are also are infected with virus and may serve as a source

  8. Which weeds are susceptible?

  9. Regional variation in the susceptibility of weeds to WSMV

  10. Increase in regional virus incidence? Vector （New York Times) SDSU Extension Host Pathogen Environment

  11. Wheat virus survey, 2008: Objectives • Determine prevalence of wheat viruses in the Great Plains (WSMV, HPV, TriMV, BYDV-PAV and CYDV-RPV) • Nine states: WY, MT, CO, KS, OK, TX, SD, ND, NE • Determine geographic distribution for TriMV & HPV • Determine if host symptoms are diagnostic among virus species for single and multiple infections • Collect and provide virus infected plant tissues to support research efforts • Increase communication about wheat viruses in the Great Plains Region

  12. Great Plains Wheat Virus Survey: 2008 WSMV % samples infected 43 40 28 38 39 61 62 27 • Range: 28 – 83 • Mean: 47 83

  13. Great Plains Wheat Virus Survey: 2008 HPV % samples infected 9 12 7 19 8 10 38 30 • Range: 7 - 41 • Mean: 19 41

  14. Great Plains Wheat Virus Survey: 2008 TriMV % samples infected 0 0 2 24 27 10 30 6 • Range: 0 - 57 • Mean: 17 57

  15. Great Plains Wheat Virus Survey: 2008 % samples infected mixed 9 9 0 0 0 0 7 2 5 1 WSMV+HPV 10 8 18 10 5 WSM+ TriMV 8 15 21 8 13 HPV+ TriMV 0 16 37 4 53 3 28

  16. Objective: Determine prevalence of wheat viruses WSMV detected in all GPDN states at high percentage infection (27 – 83 %) HPV detected in all GPDN states HPV identified in MT and WY for the first time TriMV identified in CO, KS, NE, OK, SD, TX, WY TriMV not detected in MT and ND

  17. Race Evolution in TTKS (Ug99) Lineage & Implications to Resistance Breeding Yue Jin, USDA-ARS

  18. Ug99 First reported in Uganda in 1999 --Pretorius et al. 2000 Plant Dis 84:203 • Virulent on Sr31 Sr31 is located on 1BL.1RS translocation. Also carries Lr26, Yr9. Increased adaptation and higher yield. As a result, widely spread in wheat worldwide. Helped to reduce stem rust population worldwide. • Virulence to Yr9, originated in the eastern Africa in mid 80s, caused worldwide epidemics.

  19. TTKS In 2002 and 2004, CIMMYT nursery planted in Njoro, Kenya were severely infected by stem rust. In 2005, we identified Kenyan isolates from 2004 were race TTKS. • --Wanyera, Kinyua, Jin, Singh 2006 Plant Dis 90:113

  20. Broad virulence of TTKS to North American spring wheat • US spring wheat CVs of the Northern Great Plains, known to have broad-based resistance to stem rust, were mostly susceptible (84%). • 500 CIMMYT CVs released since 1950’s, 84% were susceptible. Conclusion: Ug99 possesses a unique virulence combination that renders many resistance genes ineffective. Jin & Singh, 2006, Plant Dis:90:476-480

  21. Projected potential pathways for Ug99 based on the migration of Yr9 virulence Singh et al. 2006. CAB Review 1, 54

  22. Ug99 migration 2007 2006 2006 2003? 2005 Singh et al. 2008. Advances in Agronomy v98 2001? 2004 1998

  23. Evolution of the TTKS lineage Sr24- Sr31+ Sr36- TTKSK Our data point to: Sr24+ Sr31+ Sr36- Sr24- Sr31+ Sr36+ TTKST TTTSK Jin et al. 2008. Plant Dis. 92:923-926 Jin et al. 2009. Plant Dis. (in Press)

  24. Ramification of Sr24/Sr36 virulence to US Wheat based on testing of 2007 elite breeding germplasm % of resistance to Type Entry TTKSK TTKST TTTSK (Ug99) Sr24v Sr36v Hard red spring 89 21% 12% 21% Hard red winter 416 29% 15% 28% Soft red winter 377 27% 25% 11% Western wheat 60 3% 3% 3% Total 942 26% 18% 19%

  25. The good news • Phil and Luther are both working on it already! • Li Huang, PSPP, is starting to map genes for resistance • Fungicide trials with great results • Communication and education ramping up!

  26. Wheat stem rust fungicide trial results (2008)Stein and Gupta, SDSU Stem rust (% leaf area)

  27. Triazole + Strobilurin Triazoles

  28. Fungicide modes of action: Triazoles • FRAC group 3 • DMI (demethylation) inhibitors; biosynthesis of sterols in fungal cell membrane; spore penetration and mycelial growth • Provides 14-21 days of protection • Medium risk of resistance development • Greater mobility in plant than strobilurin fungicides • Most widely used class of fungicide in the world • Control a wide array of fungal diseases • Protective and curative effects (if applied early in disease development)

  29. Fungicide movement in the plant From: Tenuta, A., D. Hershman, M. Draper and A. Dorrence. 2007. Using foliar fungicides to manage soybean rust.. Land-Grant Universities Cooperating NCERA-208 and OMAF. Available online at http://www.oardc.ohio-state.edu/SoyRust/

  30. 20 July, 2009, Fort Ellis stem rust fungicide trial (14 d after fungicide application, 45 d after pathogen inoculation) Control Strobilurin Triazole

  31. 20 July, 2009, Fort Ellis stem rust fungicide trial (14 d after fungicide application, 45 d after pathogen inoculation) Strobilurin Control Triazole

  32. 28 July, 2009, Fort Ellis stem rust fungicide trial (22 d after fungicide application, 53 d after pathogen inoculation) Spreader row Triazole + Strobilurin

  33. Fungicide modes of action: Strobilurins • FRAC group 11 • QoI (quinone outside) inhibitors (respiration); spore germination, penetration, and mycelial growth • Provides 14-21 days of protection • High risk of resistance development because it has a very specific mode of action (they block electron transfer at the site of quinol oxidation (the Qo site) in the cytochrome bc1 complex, thus preventing ATP formation) • Originally isolated from wood-rotting fungi Strobilurus tenacellus • ‘Reduced-risk’ pesticide (pose less risk to human health than other chemical options at the time of registration by EPA) • Control a wide array of fungal diseases • Excellent preventative fungicides, but limited curative effects • “Plant health benefit” independent of disease control?

  34. Figure 1. Mobility of trifloxystrobin, an example of a QoI fungicide. http://www.apsnet.org/education/AdvancedPlantPath/Topics/Strobilurin/top.htm

  35. Preventing fungicide resistance • Limit the number of applications of a single FRAC group per season • Limit the number of consecutive applications of a single FRAC group • Mix fungicides with different modes of action (FRAC groups) • Use early in disease development

  36. Acknowledgements Dai Ito, graduate student Yue Jin, UMN Jeff Stein, SDSU

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