Early elimination of poor crosses based on an objective criterion allows increased allocation of resources only to a few promising crosses for identifying superior recombinant inbred lines (RILs) for use as pure-line cultivars in self-pollinated crops. Early generation (F2:3) prediction of frequency of superior RILs that could be derived from advanced generations of crosses is one such criterion. We predicted the frequency of transgressive RILs from two horse gram crosses (namely HPKM 320 × CRIDA18-R and IC 361290 × Palem 1) for primary branches per plant, pods per plant, pod weight per plant and grain weight per plant based on mid parental value, additive genetic effects and additive genetic variance estimated from trait means of parents, and their F2 and F2:3 generations. The predicted frequency of RILs that transgressed better parent/two checks varied with the cross and the trait within a cross. The frequencies of transgressive RILs predicted from IC 361290 × Palem 1 were higher than those predicted from HPKM 320 × CRIDA 18-R for three of the four traits. As expected, the minimum population size required to recover the transgressive RILs predicted from IC 361290 × Palem 1 was relatively smaller than that from IC 361290 × Palem 1. Increased allocation of resources for handling segregating populations derived from IC 361290 × Palem 1 is expected to result in superior RILs for use as cultivars. We believe that the objective criterion used in our study is handy in identifying superior RILs in early segregating populations derived from a few promising crosses.

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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.

Growth habit is a plant architectural trait in grain legumes with no exception of horse gram. Determinacy and indeterminacy are the two types of growth habits reported in horse gram. Relative advantages of the two types of growth habit depend on the production systems to which cultivars are targeted. Dependable information on genetics of growth habit provide clues for adopting the most appropriate selection strategy to breed high yielding horse gram varieties with desired growth habit. Taking cues from the past studies, we hypothesize that growth habit in horse gram is controlled by two genes displaying inhibitory epistasis and indeterminacy is dominant over determinacy. To test this hypothesis, we monitored the inheritance of growth habit in F1, F2 and F3 generations derived from two crosses involving parents differing for growth habit. Contrary to our hypothesis, determinate growth habit of F1s of both the crosses suggested dominance of determinacy over indeterminacy. A good fit of observed segregation of F2 plants to that of the hypothesized segregation in the ratio of 13 determinate: 3 indeterminate plants, besides confirming dominance of determinacy, suggested classical digenic inhibitory epistatic control of growth habit. These results were further confirmed in F3 generation based on goodness of fit between observed numbers of plants segregating for determinacy and indeterminacy and those expected in the ratio of 49 determinate: 15 indeterminate plants. To the best of our knowledge, this is the first report on the inheritance of growth habit in horse gram.