Commercial potato cultivars may contain several qualitative (major) resistance genes (R genes) which can protect plants against late blight, but they are not always effective because they can be defeated by new races of Phytophthora infestans. Quantitative resistance is controlled by many minor genes with additive effects and thus is more durable. This study aimed to characterize late blight resistance in Brazilian potato genotypes and evaluate a strategy to select for durable resistance. We generated potato progenies from crosses between parents with different quantitative resistance levels. The detached leaflet method was applied to test the resistance in the seedling generation with a complex race of P. infestans. Assays utilizing whole plants with inoculations of P. infestans (race 0) were performed to detect the parents’ R genes. The results allowed to identify the presence of R genes, as well as to distinguish the qualitative resistance from the quantitative resistance in the evaluated genotypes. The use of a complex race of P. infestans, compatible with R genes present in the progenies, allowed the selection for durable resistance to late blight.
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Rocha et al. (2024) studied this question.
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