Gene Estimation, Associations of Traits, and Confirmation of QTL for Common Bacterial Blight Resistance in Common Bean

Abstract

Common bacterial blight, incited by Xanthomonas campestris pv. phaseoli (Xcp), is a serious disease of common bean(Phaseolus vulgaris L.). Gene estimation, associations of traits, and confirmation of QTL for resistance to Xcp were investigated in a recombinant inbred population derived from the backcross BC2F6 PC-50 (susceptible to Xcp) × XAN-159 (resistant to Xcp). One or two genes from XAN-159 controlled leaf resistance to Xcp. One major gene from XAN-159 was involved in controlling pod resistance to Xcp. Low (+0.24) to intermediate (+0.57 and +0.75) Pearson correlations were observed between leaf and pod reactions to Xcp. Purple flower color was associated with leaf and pod resistance to Xcp but not days to flower. One to 2 QTLs explained from 20 to 51% of the total phenotypic variation for leaf reactions to 5 Xcp strains. Two QTLs explained from 20 to 22% of the total phenotypic variation for pod reactions to Xcp strains EK-11 and DR-7. A marker BC437.1050 was associated with leaf and pod resistance to 5 Xcp strains in nearly all experiments, and accounted for 13% to 45% of the phenotypic variation for these traits. A unassigned marker D13.1000 was associated with only pod resistance to Xcp strains EK-11 and DR-7. Gene number (1 or 2) estimations and number of QTL (1 or 2) detected for resistance to Xcp generally agree. The confirmed marker BC437.1050 is expected to be useful in breeding programs for resistance to Xcp.