Vol. 9, Special Issue 12, Part C (2025)

Drought stress induces substantial variation in key morphological traits that determine yield potential and adaptation strategies in groundnut. Understanding the inheritance of these traits across generations is essential for identifying suitable breeding strategies aimed at improving drought-tolerant cultivars. This study evaluated nine morphological traits viz., days to 50 percent flowering, days to maturity, number of branches per plant, number of mature pods per plant, haulm yield per plant, dry pod yield per plant, hundred kernel weight, shelling percentage and harvest index on dry weight basis, across six generations (P₁, P₂, F₁, F₂, BC₁ and BC₂) under irrigated and drought-stress conditions. The data obtained were subjected to generation mean analysis to assess the nature and magnitude of gene effects. The analysis of variance revealed significant differences among all six generations for all the traits studied under both irrigated and drought conditions, indicating the presence of considerable variability in the material assessed. F₁ means were generally intermediate or exceeded the better parent, suggesting incomplete dominance for several traits. Under irrigated conditions, TAG-24 exhibited superiority for yield-related traits, while the drought-tolerant parent ICG 4670 performed better under water stress. F₂ population was superior for dry pod yield under irrigation, while under drought, P₂ (ICG 4670) and BC₂ (F₁ × ICG 4670) was superior. BC₁ (F₁ × TAG-24) recorded higher shelling percentage and harvest index under irrigation, whereas BC₂ (F₁ × ICG 4670) performed better under drought for the same traits.

Generation mean analysis revealed that the simple additive dominance model was inadequate and thus a six-parameter model was employed. Significant A, B, C and D scaling tests and joint scaling test indicated the presence of higher-order interactions. Under irrigated conditions, dominance (h) and dominance × dominance (l) interactions were significant for days to 50% flowering, days to maturity, number of branches per plant, number of mature pods, haulm yield and dry pod yield, suggesting the prevalence of non-additive gene action. Under drought stress, dominance and dominance × dominance effects were again predominant for dry pod yield, implying that these traits can be improved through hybridization and delayed selection.

Additive (d) and additive × additive (i) gene effects were significant for certain traits including dry pod yield and number of mature pods per plant, indicating that early-generation selection could be effective for these traits. Duplicate epistasis was more common than complementary epistasis under both environments, suggesting mild selection in early generations and more intense selection in advanced generations. The integration of morphological attributes in breeding programmes can significantly enhance screening efficiency and the development of drought-resilient groundnut varieties.