Line × Tester Analysis: Potential Genetic Contributions to Yield and Morpho-Physiological Traits in Bread Wheat (Triticum aestivum L.) Under Contrasting Water Regimes

This study used a line × tester design to evaluate eight lines, five testers, and 40 F1 hybrids at the Cereal Crops Research Institute (CCRI), Pirsabak, Pakistan, during the 2023–2024 growing season under irrigated and rainfed conditions using a randomized complete block design with three replications. An integrated analysis of combining ability, heterosis, variance components, and proportional genetic contributions was used to assess the variation and potential genetic contributions associated with yield and morpho-physiological traits under contrasting water regimes. SCA-associated effects contributed substantially to the variation observed for several traits, particularly under the rainfed conditions. Broad-sense heritability was high for days to heading, grain yield per plant, and harvest index under irrigated conditions, and for biological yield, tiller number, and spike weight under rainfed conditions. Akbar-19, HPYT-2, and Abaseen-21 showed favorable GCA effects for grain yield under the tested rainfed conditions, while AAS-11 × Kohat-10 and Punjab-11 × Pirsabak-2005 showed favorable performance across the two tested water regimes. Better-parent heterosis for grain yield was highest and most consistent in AAS-11 × Kohat-10, with spike weight and grains per spike showing important associations with grain yield under the tested rainfed conditions.