The present investigation was carried out at Research Farm of Tirhut College of Agriculture, Dholi, Muzaffarpur, Bihar. The experimental material consisted of three genotypes of resistant mungbean and urdbean donor each viz., HUM-16, TMB-37, Samrat and Pant U-31, Uttara, Sekhar, respectively; with a susceptible donor of LGG 450 and Barabanki local for mung and urd, respectively. Six intraspecific and four interspecific crosses were made and P 1 , P 2 , F 1 , F 2 BC 1 , BC 2 population were grown in RBD design with three replications. The observations were recorded for thirteen different quantitative as well qualitative traits viz., Days to 50 flowering, Plant height (cm), Number of primary branches, Cluster per plant, pods per cluster, Number of pods per plant, Days to maturity, Pod length (cm), Grains per pod, 100 seed weight (g), Harvest index, Phenol content (mg) and Grain yield per plot (kg).n Basedon the joint scaling test few intraspecific combinations showed the presence of epistasis; whereas in most of the interspecific crosses epistasis was observed. As per the three parameters model additive and/or dominant components seems to play an important role in the inheritance of most of the yield attributing traits in intra and interspecific crosses. As evident from the six parameter model, preponderance of significant reducing (-ve) additive gene effects in intraspecific crosses were observed, whereas additive and dominance components were equally important in interspecific crosses for the expression of most of the yield attributing traits. Among epistatic interactions additive x additive gene effects for days to 50 per cent flowering and dominant x dominant gene effect for 100 seed weight in four intraspecific crosses, whereas in interspecific crosses all three types of epistatic interactions were observed for the expression of most of the yield attributing traits. In most of the intra as well as interspecific crosses, duplicate type of epistasis was observed.
