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Initiated in 2002 by USDA-CSREES with homeland security funding

Biotic pests in cereal crop production: plant pathogens Wheat streak mosaic virus and Stem Rust Ug99. Mary Burrows, Dai Ito, Matt Moffet, Zach Miller, Fabian Menalled, Mareike Johnston, Luther Talbert, Tom Blake, and Phil Bruckner.

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Initiated in 2002 by USDA-CSREES with homeland security funding

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  1. Biotic pests in cereal crop production: plant pathogensWheat streak mosaic virus and Stem Rust Ug99 Mary Burrows, Dai Ito, Matt Moffet, Zach Miller, Fabian Menalled, Mareike Johnston, Luther Talbert, Tom Blake, and Phil Bruckner

  2. Initiated in 2002 by USDA-CSREES with homeland security funding • Goal: to provide diagnostic capability to the nation’s agricultural system • Five regional hubs with responsibility for diagnostics, funding, public relations, epidemiology, and training

  3. Regional Networks of NPDN North Eastern Plant Diagnostic NetworkCornell University North Central Plant Diagnostic NetworkMichigan State University Western Plant Diagnostic NetworkUniversity of California, Davis National Agricultural Pest Information System Purdue University Great Plains Diagnostic NetworkKansas State University South Eastern Plant Diagnostic NetworkUniversity of Florida

  4. Network Responsibilities • Data collection (detectors/diagnosticians) • Communications system • Information storage and management • Data analysis • New events and analysis of new appearance • Pattern recognition • Unusual patterns of endemic problems • GIS • Event propagation • Tracking • Reporting and alerts • Link to State Departments of Ag and US regulatory • agencies

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

  6. 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

  7. Disease cycle of WSMV

  8. Weed Host: Volunteer Wheat

  9. WSMV in Montana weeds, 2008 Volunteer wheat is the best non-crop host, but weed species are also are infected with virus and may serve as a source

  10. Which weeds are susceptible?

  11. Regional variation in the susceptibility of weeds to WSMV Wheat = 1

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

  13. 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

  14. Objective: Determine prevalence of wheat viruses WSMV detected in all GPDN states at high percentage infection (10 – 83 %) HPV detected in all GPDN states HPV identified in MT and WY for the first time TriMV identified in all states, all but KS new reports

  15. Winter wheat: inoculated trials

  16. Winter wheat: inoculated trials

  17. Yield reductions due to spring inoculation with WSMV, 2008 & 2009

  18. Spring wheat: inoculated trials

  19. Spring wheat: inoculated trials

  20. Yield reductions due to inoculation with WSMV, 2008 & 2009

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

  22. 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

  23. 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

  24. 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

  25. 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)

  26. 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%

  27. Current status of Ug99 • New races constantly evolving • Ug99 stalled in Iran due to long drought • If moves to Pakistan/India will affect 15% of world’s wheat crop that feeds 1 billion of the world’s poorest people • Strain of stem rust in India that overcomes Sr25 • ‘Likely’ Ug99 has already spread beyond Iran - Rick Ward, co-coordinator of the Durable Rust Resistance in Wheat project, based at Cornell university; http://rustopedia.org/traction/permalink/Resources905

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

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

  30. The good news • Phil and Luther are both working on it already! • Li Huang, PSPP, has identified spring wheat mutants from a population derived by Mike Giroux with resistance to leaf, stem, and stripe rust – including all Ug99 derivatives • Fungicide trials with great results • Communication and education ramping up!

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

  32. Triazole + Strobilurin Triazoles

  33. 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)

  34. 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/

  35. 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?

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

  37. 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

  38. Stem rust fungicide trial • RateActive IngredientCompany • Control • Proline 480 SC 5.3 oz Prothioconazole Bayer • 3. Prosaro 421 SC 7.5 oz Tebuconazole + Prothioconazole Bayer • 4. Quilt 14 oz Azoxystrobin + PropiconazoleSyngenta • 5. A15590C 14 oz Azoxystrobin + PropiconazoleSyngenta • 6. Alto 100SL 4 oz CyproconazoleSyngenta • 7. Caramba 13.5 oz Metconazole BASF • 8. Twinline 9 oz Pyraclostrobin +Metconazole BASF • 9. Headline 2.09EC 7.5 oz Pyraclostrobin BASF • 10. Gem 500 SC 2.4 oz Trifloxystrobin Bayer

  39. Control (no fungicide), 14 daa

  40. Strobilurin fungicides, 14 daa Headline Gem 500 SC

  41. Strobiliurin + Trizole, 14 daa Quilt Quilt Xcel

  42. Strobiliurin + Trizole, 14 daa Prosaro Twinline

  43. Trizole fungicides, 14 daa Alto Caramba Proline

  44. Compare sprayed and unsprayed plots

  45. Yield, stem rust fungicide trial2009, Bozeman d bcdcd cd bcbc bc b a a

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