Disease Resistance Howard F. Schwartz Research & Extension Plant Pathologist Dept. of Bioagricultural Sciences & Pest Management
Resistance Reduces or Eliminates: Direct reduction of yield Additional cost of controls Examples: True genetic resistance PhysiologicalAnatomicalMechanicalToleranceEscape
Resistance Levels of Disease Resistance: ImmunityResistanceToleranceEscapeKleindusity
Resistance
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Resistance
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
Resistance Resistance Continuum: Very Susceptible Susceptible Moderately Susceptible Intermediate Moderately Resistant Resistant Very Resistant
Resistance
Resistance Obtaining Disease Resistance: SelectionHybridizationGrafting Induced Mutation Induced Resistance NutritionPhytoalexinChemotherapy Genetic Engineering
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Inoculation
Inoculation
University of Idaho Susceptible Resistant
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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
Resistance Strategies for Managing Resistance Failures: Nonspecific Major Gene Resistance Gene Stacking or Pyramiding Multilines Gene Deployment
Resistance
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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 )
Spatial Pattern -IYSV
ONION IYSV Disease Severity Guidelines
Variety Trials in CO ( ) & WA ( ): 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
Field Tolerance to Thrips and/or IYSV C. Boateng, K. Otto, M. McMillan, W. Cransaw, M. Camper, S. Szostek, H. Schwartz
Promising Entries for Field Tolerance to IYSV / Thrips 2009 & CO (** and NM): PI Chile “Calderana” PI **Spain PI **U.S.A. “San Joaquin” PI U.S.A. “Yellow Sweet Spanish Winegar” PI U.S.A. “Yellow Sweet Spanish” CO Variety Trial: NunhemsNUN7606ON CrookhamOLYS03-207, 05N5, ; OLYX06-25 D. Palmer“Mesquite” CO:selections from PIs , , , , Mesquite, 05N5, B5336C (P C)
Genetic Resources
Evaluation Protocols