Use of Marker-assisted Selection to Breed for Resistance to Common Bacterial Blight in Common Bean

Abstract

Common bacterial blight (CBB), incited by the bacterial pathogen Xanthomonas axonopodis pv. phaseoli (Smith) Vauterin et al., is one of the most serious seed-borne diseases of common bean (Phaseolus vulgaris L.) worldwide. Although previous attempts to breed CBB-resistant bean cultivars have had limited success due to the quantitative nature of resistance, progress in marker-assisted selection has created new opportunities for breeders to improve the selection process. The potential of independent linked markers for indirect selection of CBB resistance was evaluated in field experiments in East Lansing and Saginaw, Mich. The presence of the SU91 marker was correlated with lower CBB leaf scores in East Lansing (r = −0.50***) and Saginaw (r = −0.59***) and correlated with pod resistance in Saginaw (r = −0.48***). SU91 exhibited a slight negative correlation with yield (r = −0.20*) in East Lansing but showed no association with yield in Saginaw. Plant selections carrying SU91 were crossed with a different source of CBB resistance linked to the sequence-characterized amplified region marker BC420 on bean linkage group B6. The effects of SU91 and BC420 markers were examined in two greenhouse studies. The presence of SU91 was correlated with lower CBB disease ratings for leaves (r = −0.20*) and pods (r = −0.27***). Presence of BC420 was only correlated with low pod ratings (r = −0.19*) in one experiment and CBB leaf resistance (r = −0.18*) in the second experiment. Presence of both markers resulted in lower levels of CBB resistance than provided by either marker alone, possibly indicating epistatic interactions between the independent loci conditioning CBB resistance in common bean.