1. Disease Resistance Howard F. Schwartz Research & Extension Plant Pathologist Dept. of Bioagricultural Sciences & Pest Management

2. Resistance Reduces or Eliminates: Direct reduction of yield Additional cost of controls Examples: True genetic resistance PhysiologicalAnatomicalMechanicalToleranceEscape

3. Resistance Levels of Disease Resistance: ImmunityResistanceToleranceEscapeKleindusity

4. Resistance

5. Resistance

6. Resistance

7. Resistance

8. Resistance

9. Resistance Characteristics of Resistance: General Resistance - is quantitative due to several genes - operates against all races of a pathogen = horizontal, nonspecific, multigene, polygenic, minor gene, adult or mature plant, field, uniform, durable, incomplete, partial resistance Specific Resistance - is qualitative due to a single or few genes - operates against individual races of a pathogen = vertical, race-specific, single gene, monogenic, major gene, seedling, differential resistance

10. Resistance Resistance Continuum: Very Susceptible Susceptible Moderately Susceptible Intermediate Moderately Resistant Resistant Very Resistant

11. Resistance

12. Resistance Obtaining Disease Resistance: SelectionHybridizationGrafting Induced Mutation Induced Resistance NutritionPhytoalexinChemotherapy Genetic Engineering

13. Resistance

14. Inoculation

15. Inoculation

17. University of Idaho Susceptible Resistant

18. Resistance

19. Resistance

20. Resistance

21. Resistance

22. Resistance Mechanisms: Mechanical Resistance cuticle, gums, resins, modified cell walls, lignin & suberin deposits, barrier zone formation, cork barriers, lignitubers & papillae Chemical Resistance present before invasion such as catechol, protocatechuic acid, chlorogenic acid, caffeic acid, borbonol Functional Resistance - stomatal morphology, size, or closure; closed flowers; hypersensitivity; slow rusting

23. Resistance Strategies for Managing Resistance Failures: Nonspecific Major Gene Resistance Gene Stacking or Pyramiding Multilines Gene Deployment

24. Resistance

25. Resistance

26. Resistance

27. Resistance

28. Iris Yellow Spot Virus Emerging Disease in the World Confirmed in all western USA states and GA, TX, NY, Canada, Mexico Vectored by onion thrips (Thrips tabaci )

29. Spatial Pattern -IYSV

30. ONION IYSV Disease Severity Guidelines

31. Variety Trials in CO (2003-05) & WA (2004-05): Subset of 17 yellow entries common to the 3 tests with moderate to severe IYSV outbreaks: 8 entries had green leaf color with >10% lower incidence of IYSV and 33% higher marketable yield than 9 yellow entries with blue-green leaves

32. Field Tolerance to Thrips and/or IYSV C. Boateng, K. Otto, M. McMillan, W. Cransaw, M. Camper, S. Szostek, H. Schwartz

33. Promising Entries for Field Tolerance to IYSV / Thrips 2009 & 2010 - CO (** and NM): PI 258956Chile “Calderana” PI 264320 **Spain PI 546140 **U.S.A. “San Joaquin” PI 546188U.S.A. “Yellow Sweet Spanish Winegar” PI 546192U.S.A. “Yellow Sweet Spanish” 2009 - CO Variety Trial: NunhemsNUN7606ON CrookhamOLYS03-207, 05N5, 03-209; OLYX06-25 D. Palmer“Mesquite” 2011 - CO:selections from PIs 258956, 288909, 343049, 546188, Mesquite, 05N5, B5336C (P53-364-2C)

34. www.alliumnet.com Genetic Resources

35. Evaluation Protocols