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Background: Allocation of resources only to a few promising segregating populations that are likely to result in high frequency of transgressive recombinant inbred lines (RILs) for use as pure-line cultivars would help enhance efficiency of breeding self-pollinated crops including dolichos bean. The use of an objective criterion to identify promising segregating populations is therefore assumes importance. The prediction of frequency of transgressive RILs that could be derived from advanced generations of segregating populations of crosses is one such criterion. Methods: We predicted the frequency of RILs that transgressed the better parent (HA 5) from two reciprocal crosses derived from two elite but genetically diverse parents (HA 4 and HA 5) for four quantitative traits based on estimates of mid parental value [m], additive genetic effects [a] and additive genetic variance [σ2A]. Result: The frequency of transgressive RILs predicted from H 5 × HA 4 was higher than those predicted from H 4 × HA 5 for primary branches plant-1, pods plant-1 and grain weight plant-1, while it was comparable between the crosses for pod weight plant-1. The required minimum population size was relatively smaller to recover the transgressive RILs from the cross which was predicted to result in higher frequency of RILs than that was predicted to result in lower frequency of RILs.

Development of high yielding cultivars with determinate growth habit in photoperiod insensitive (PIS) background is one of the major objectives of breeding grain legumes crops including dolichos bean. A thoroughly validated genetic basis is a prerequisite for breeding dolichos bean for determinate growth habit in PIS background. Based on the published reports by researchers of our laboratory and those by others, and our unpublished data, we hypothesized that the number and mode of action of genes controlling growth habit differ with degree of photoperiod sensitivity of the genetic material used to investigate the inheritance of growth habit in dolichos bean. To test this hypothesis, we compared the number and mode of action of genes controlling growth habit between segregating generations in Photoperiod sensitive (PS) and those in PIS genetic backgrounds. While indeterminate and determinate plants segregated in 15:1 ratio in F2 populations derived from crosses between determinate PIS and indeterminate PIS parents, they segregated in 9:7 ratio with indeterminacy being dominant in F2 populations derived from crosses between determinate PIS and indeterminate PS parents. These patterns of segregation (15:1 and 9:7) in favour of indeterminate and determinate plants, respectively in F2 populations were confirmed in F3 populations of PIS and PS genetic backgrounds based on good fit between observed and expected ratios (55:9 and 29:35, respectively) in favour of indeterminate and determinate plants, respectively. The patterns of segregation in F2 populations were further confirmed in F3 populations based on good fit between observed and expected ratios of 3:1 segregating and non-segregating families, and of 3:1 indeterminate and determinate non-segregating families, respectively.