POLYGENIC RESISTANCE OF PEPPER TO POTYVIRUSES CONSISTS OF A COMBINATION OF ISOLATE-SPECIFIC AND BROAD-SPECTRUM QUANTITATIVE TRAIT LOCI

At least six potyviruses infect pepper crops around the world. Only mo nogenic resistance with isolate-specific effects or broad-spectrum eff ects against potyviruses has been identified. Quantitative trait loci (QTLs) for resistance to two potato virus Y (PVY) isolates and to poty virus E have been mapped in a doubled-haploid progeny from the hybrid between the line Perennial with resistance factors against several pot yviruses and the line Yolo Wonder, with 172 DNA markers. Eleven chromo somal regions were found to be associated with quantitative resistance to PVY and potyvirus E by both analysis of variance and nonparametric tests, This resistance results from the association of a major-effect QTL and several minor-effect QTLs. Two minor-effect QTLs originated f rom the susceptible parent. In addition to additive-effect QTLs, inter actions between QTLs were also identified, Based on their spectrum of action, we discriminated QTLs with PVY isolate or potyvirus-specific e ffect and loci involved in the resistance to several distinct potyviru ses. The locations of QTLs were compared with loci having known qualit ative effects against potyviruses; QTLs for PVY and potyvirus E resist ance were detected in the vicinity of the pvr2 and pvr6 loci. The orig in of the broad-spectrum resistance against potyviruses and the relati onships between major genes and QTLs are discussed.