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Simple Models of Durable Resistance to Plant Diseases

Robert Bowden: USDA ARS

<div>Durable resistance to diseases is the ultimate aim of many crop improvement programs, however, a stronger theoretical basis is needed to inform decision-making about strategies for achieving durability. We developed two simple models that describe how durability can be a result of either: 1) a low probability that virulent pathogen genotypes arise from mutation or recombination, or 2) low relative fitness of those virulent genotypes. In the first model, the probability of occurrence of new virulent pathogen genotypes is a negative exponential function of population size, mutation or recombination rate, and establishment efficiency. In the second model, durability is predicted when the selective advantage associated with defeat of the resistance gene is less than the fitness cost of virulence. Likely success or failure of any specific strategy for durable resistance can be evaluated if the model parameter values can be estimated for a given situation. We also propose guidelines for assessing the intrinsic durability of resistance genes and designing durable combinations of qualitative genes or combinations of both qualitative and quantitative genes.</div>

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