A key QTL cluster is conserved among accessions and exhibits broad-spectrum resistance to Phytophthora capsici: a valuable locus for pepper breeding

Developing cultivars carrying effective resistance against destructive pathogens has become a priority for breeders. While little is currently known about the genetic basis of durable resistance, it is generally associated with polygenic and broad-spectrum resistance. In this study, we assessed the spectrum of resistance to Phytophthora capsici conferred by a major effect quantitative trait locus (QTL) that has been detected in all of the resistant pepper accessions studied to date. After adding new markers derived from tomato sequences and those from pepper reported in the literature to three maps of pepper chromosome P5, we detected a QTL cluster involved in P. capsici resistance. By means of meta-analyses, we determined the occurrence of these QTLs in different genetic backgrounds and with different P. capsici isolates. Comparative mapping with tomato and potato highlighted a complex mosaic of Phytophthora resistance loci on colinear chromosome segments. We tested different lines with and without one of these QTLs, Pc5.1, with four isolates that we determined to be genetically distinct. Our data demonstrate that Pc5.1 is active against 12 isolates from different geographical origins and that it is conserved in all of the resistant accessions tested. We propose that this QTL is a key element responsible for the broad-spectrum resistance to P. capsici and, therefore, is a valuable locus for improving the effective resistance of pepper to P. capsici.