Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Designer baby wikipedia , lookup
Fetal origins hypothesis wikipedia , lookup
Genome (book) wikipedia , lookup
Neuronal ceroid lipofuscinosis wikipedia , lookup
Epigenetics of neurodegenerative diseases wikipedia , lookup
Genetically modified crops wikipedia , lookup
Horizontal Resistance to Plant Diseases John Navazio Organic Seed Alliance Plant Disease Basics • Pathogen – disease causing agent • Disease - the resultant effects of parasitism by a pathogen • Resistance – any inherited characteristic of a host plant which lessens the effects of parasitism • Tolerance – parasitism is not impeded, but the host suffers only marginal loss of yield and/or quality How Do Pathogens Cause Disease? • All elements of the Disease Triangle are present; Pathogen, Host, & Environment • Pathogen must be present and reach the surface of the host • Pathogen must grow when environmental conditions are favorable (establishment) • Pathogen must colonize (colonization) • Pathogen must reproduce (reproduction) Vertical Resistance to Disease • Term coined by Vanderplank in 1950s • Vertical resistance is AKA “qualitative resistance” or “race specific resistance” • Almost always conferred by a single gene • Each resistance gene usually confers resistance to one race of the pathogen • “Hypersensitive Reaction” is dramatic • Easy to recognize and to screen for by breeders • These single genes almost always “overcome” by new races of the pathogen Horizontal Resistance to Disease • Term coined by Vanderplank in 1950s • Horizontal resistance is AKA “quantitative resistance” or “durable resistance” • Always conferred by multiple genes • Confers a level of resistance to all races of the pathogen – also “new contact” races • It is a “rate reducing” process to the… – establishment – colonization – reproduction • It is equivalent to a “strong constitution” Horizontal Resistance to Disease • Horizontal resistance (HR) is not complete • The pathogen is able to survive – thereby it is possible to have a stable ecological balance between the pest and crop • By allowing a number of races to survive, some more virulent, some less virulent, then when they intermate/genetic change there will be a wide range of virulence in the population of the pathogen Goode Thoughts • “HR requires high management by the breeder of both the pathogen and the host, but requires little by the grower” • “VR breeders and pathologists have been patching their mistakes and bragging about how big their patches are!” • Quotes from Dr. Jack Goode’s lectures in Plant Pathology, Univ. of Arkansas, 1978