In common with other grain legumes, the growth habit in horse gram is one of the domestication-driven adaptive traits. Horse gram exhibits determinate and indeterminate types of growth habits. Determinate genotypes have non-overlapping vegetative and reproductive phases combined with a compact growth habit which enables farmers to produce horse gram in intercropping and multiple cropping systems, a common practice for sustainable agriculture production. Also, synchronous flowering, and pod development and maturity of determinate genotypes enable mechanical harvesting. Empirical studies have indicated a greater grain yield potential of indeterminate compared to determinate genotypes. However, we hypothesize that indeterminate and determinate genotypes do not differ for their grain yield potential if they are in isogenic genetic backgrounds. To test this hypothesis, we compared eight pairs of near isogenic (NI) indeterminate and determinate genotypes for their grain yield potential during two rainy seasons in one location and one rainy season in another location. The eight pairs of NI determinate and indeterminate genotypes differed significantly in each of the three test environments. Indeterminate genotypes produced a greater pod (harvestable) and grain (marketable) yields than their determinate counterparts only in a few genetic backgrounds. These results thus support our hypothesis that determinate genotypes are comparable to indeterminate ones, if not better than the latter.

Nine characters contributing to seed yield were measured on 20 accessions of horse gram (Macrotyloma uniflorum (Lam.) Verd), and subjected to genetic divergence analysis using Mahalanobis statistic and mapping using DIVA-GIS. The accessions were collected from two eco-geographical regions of Andhra Pradesh (India) – North Coastal and Rayalaseema. Based on D2 values the genotypes were grouped into five clusters. Genetic diversity was not related to eco-geographical distribution. The greatest inter-cluster distance separated clusters II and V, followed by clusters IV, and V, III and IV. Entries in clusters V and II appear suitable as parents for horse gram improvement. The Rayalaseema region is the source of useful variation for days to flowering, maturity and yield.