DNA Markers for Selection of Late Blight Resistant Potato Breeding Lines

Abstract

Potato late blight, caused by the oomycete Phytophthora infestans, is one of the most devastating diseases in the agricultural sector around the world. Many genes (R genes) conferring resistance to late blight have been identified in various potato species and most of these R genes have been used in potato breeding. The aim of this study was to develop and validate PCR-based assays for the R genes Rpi-blb1, Rpi-blb2, Rpi-blb3 and Rpi-bt1, to distinguish between late blight resistant and late blight susceptible potato progeny in the given breeding background. A total of 100 breeding progeny were screened for the presence of these R genes and tested for resistance against P. infestans mating type A2, genotype US-8 strain, using detached leaf and tuber rot assays. PCR products for the Rpi-blb1 and Rpi-bt1 resistance genes were identified in the resistant progeny but were absent in the susceptible ones; therefore these PCR assays could differentiate between late blight resistant and susceptible plants. Genotypic data from the DNA markers derived from the Rpi-blb1 and Rpi-bt1 genes was found to correlate with the phenotypic data for foliar late blight but not with data for tuber rot. Our results demonstrate that markers derived from these two R genes could be useful for marker-assisted selection (MAS) for foliar late blight resistance in potato breeding programs.