Progress in Breeding Andean Common Bean for Resistance to Common Bacterial Blight

Abstract

ABSTRACTCommon bacterial blight is a severe disease of common bean (Phaseolus vulgaris L.) worldwide. Use of resistant cultivars is crucial for its control. The objectives were to (i) assess the progress made in breeding large‐seeded Andean bean developed between 1974 and 2010 and (ii) determine their resistance‐linked sequence characterized amplified region (SCAR) marker composition. Ten Andean and four Middle American common bacterial blight resistant beans including checks were evaluated in the greenhouse in 2011. Bacterial strains ARX8AC and Xcp25 were used to inoculate primary and trifoliolate leaves. The mean disease score of the trifoliolate was 5.0 and of the primary leaf was 2.8. Strain Xcp25 had a mean score of 3.8 in primary and 5.9 in trifoliolate leaves. The respective scores for ARX8AC were 1.9 and 4.2. Andean ‘Montcalm’, with the SAP6 quantitative trait loci (QTL) and USDK‐CBB‐15, and USWK‐CBB‐17, with the SAP6 and SU91 QTL, showed an intermediate response to ARX8AC and a susceptible response to Xcp25. Middle American VAX 1 with SAP6, Andeans 08SH‐840 and CXR 1 with SAP6 and SU91, and RCS52‐2, RCS53‐3, and RCS63‐5B with SU91 and BC420 were resistant or intermediate to both strains. Middle American VAX 3 and VAX 6, with SAP6 and SU91, had the highest levels of resistance to ARX8AC, but their responses to Xcp25 were similar to the latter Andean group. Thus, significant improvement has been achieved, but breeding for yet higher levels of resistance, recovery of commercial seed types, and improving yield and other agronomic traits should be emphasized.