MARKER-ASSISTED SELECTION TO IMPROVE DROUGHT RESISTANCE IN COMMON BEAN

Breeding for a quantitative trait like drought resistance would be fac ilitated by the development of a method of marker-assisted selection ( MAS) that is capable of identifying high performing genotypes in early generations, Two recombinant inbred populations were grown from 1990 to 1994 at eight locations in Michigan and Mexico under stress and non stress conditions to identify random amplified polymorphic DNA (RAPD) markers associated with drought resistance in common bean (Phaseolus v ulgaris L). Six-hundred random decamer primers were screened against t he parents of the two populations, 50% of which were polymorphic, Seve nty of these polymorphic primers were screened against each population , Using one-way analysis of variance and multiple regression, four RAP D markers were identified in one population and five in another that w ere consistently and significantly associated with yield under stress, yield under nonstress, and/or geometric mean yield across a broad ran ge of environments, To test the effectiveness of MAS for drought resis tance, markers were used to select genotypes from either extreme, Yiel d data from three locations were examined to evaluate the effectivenes s of these marker-based selections. Marker-assisted selection in the S ierra/AC1028 population was found to be effective in Michigan under se vere stress and ineffective in Mexico under moderate stress, The five RAPD markers used for MAS in the Sierra/Lef-2RB population improved pe rformance 11% under stress and 8% under nonstress, whereas conventiona l selection based on yield performance failed to increase performance, response to conventional selection was three times greater in the Sie rra/AC1028 population, supporting the conclusion that the effectivenes s of MAS is inversely proportional to the heritability of the trait un der examination.