Genetics of growth habit in horse gram (Macrotyloma uniflorum (Lam.)Verdc.)

Abstract 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.