Genetic mapping of quantitative resistance to race 5 of Pseudomonas syringae pv. phaseolicola in common bean

Halo-blight is an important worldwide bacterial disease of common bean (Phaseolus vulgaris L.) caused by Pseudomonas syringae pv. phaseolicola. Nine races of the pathogen and five race-specific resistance genes have been previously described. However, a quantitative response to this pathogen has also been described. The objective of this study was to identify halo-blight resistance loci linked to molecular markers that could be used in resistance breeding. Chromosomal regions related to race 5 halo-blight resistance were localized on a genetic map of RAPD and AFLP molecular markers and constructed by the analysis of a “Jules” × “Canela” F₂ progeny. “Jules” shows quantitative resistance to halo-blight and “Canela” is a very appreciated but susceptible Spanish bean landrace. Two QTL for resistance to halo-blight were mapped in two linkage groups. There were four large groups, with 14–22 molecular markers each, five with 4–8 markers each, and three with 2 or 3 markers each.