HERITABILITY AND SOURCES OF ASCOCHYTA BLIGHT RESISTANCE IN COMMON BEAN

Common bean germ plasm (Phaseolus vulgaris) with intermediate Ascochyt a blight (caused by Phoma exigua var. diversispora) resistance has bee n identified at CIAT. The heritability and inheritance of resistance t o this pathogen were studied in three resistant climbing bean sources. Narrow-sense heritability estimates determined by the regression of t he F2-derived F4 line means on F2-derived F3 line means from crosses C arioca (S) X G 10817 (R) and G 10088 (S) X G 10747 (R) were low to mod erate (0.19-0.64), depending on the cross and character measured. A ge neration means analysis of resistant parents G 10817 and G 10823 cross ed with the susceptible parent G 12488 indicated that additive, domina nce, and epistatic effects were important in the inheritance of resist ance. Evaluation of lines for resistance should be conducted in advanc ed generations in replicated trials.