C. Caranta et al., POLYGENIC RESISTANCE OF PEPPER TO POTYVIRUSES CONSISTS OF A COMBINATION OF ISOLATE-SPECIFIC AND BROAD-SPECTRUM QUANTITATIVE TRAIT LOCI, Molecular plant-microbe interactions, 10(7), 1997, pp. 872-878
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.