LAUSR

Abstract. Powdery mildew (PM) is a devastating disease of many legume species, including common bean. In this work, we assessed the responses of 108 dry and snap bean accessions to PM, and characterised the genetic control of the resistance in three bean genotypes. Resistance tests under controlled conditions led to the identification of 11 dry bean accessions with total resistance. However, no snap bean accessions showed total resistance, although two cultivars showed mixed phenotypes including seedlings with total resistance. The inheritance of resistance was analysed in three F2:3 populations involving the resistant bean genotypes BelNeb, G19833 and BGE003161. In the three populations, the segregation for PM resistance fit the expected ratio for one dominant gene. The resistance loci were mapped to the beginning of the linkage group Pv04. The physical positions of the flanking markers indicated that the three resistance genes were located between the physical positions 0 and 1.09 Mb. This work provides new PM-resistance sources and markers linked to resistance genes, which will be very useful in common bean breeding programs focussed on protecting bean crops against this disease.