Modelling the effect of gene deployment strategies on durability of plant resistance under selection

Genetic resistance in crop plants is a cornerstone of disease management in agriculture. Such genetic resistance is often rapidly overtaken due to selection in the pathogen population, resulting in an arms race between plant breeders and the pathogen population. Here we ask whether there are strategies that can prolong the useful life of plant resistance genes. In a modelling study we compare three basic strategies: gene pyramiding, sequential use, and simultaneous use, and combinations of these. We furthermore explore the effects of fraction of host area, fraction of resistant host and the threshold fraction of virulence in the pathogen population at which resistance is considered overtaken on the useful life of resistance genes. We found that pyramiding is not always the most durable solution. Model results indicate that the most durable deployment strategy depends on the threshold fraction at which resistance is considered overtaken. This threshold fraction will depend on the economic value of the crop, and whether damage is acceptable. Pyramiding is only the most durable solution if the threshold is low. Otherwise, simultaneous use of single-gene resistant varieties is the most durable solution.