Water scarcity is a stress factor that drastically affects and reduces crop productivity. The objective of this study was to explore the influence of water deficiency on seed cotton yield and its associated traits and to study the coefficient of variances, heritability, and GG for various traits in upland cotton (Gossypium hirsutum L). Four cotton cultivars, i.e., Ishonch, Navbakhor-2, C-6524, and Tashkent-6, and their F-1 diallel hybrids were grown in a randomized complete block design with factorial arrangement and four replications under optimal and deficit irrigation conditions during 2018-2019 in the Tashkent region of Uzbekistan. Significant (P <= 0.01) differences were observed among the parental genotypes and their F1 hybrids for boll weight, 100-seed weight, seed cotton yield, and lint%. The genotypes exhibited significant (P <= 0.05) and nonsignificant differences for bolls per plant under water deficit and optimal irrigation conditions, respectively. Overall, deficit irrigation conditions negatively affected the yield-contributing traits and eventually the seed cotton yield. The parental cultivars Ishonch and Navbakhor-2 and their F1 diallel hybrids were found to be more stable and performed better than the other genotypes under both water regimes. On average, the genotypic and phenotypic variances for various traits were greater under water deficit conditions than under the optimal irrigation regime. Broad-sense heritability estimates were the highest for boll weight, 100-seed weight, seed cotton yield, and lint% but were low for bolls per plant. Seed cotton yield revealed highly significant positive associations with all traits under optimal irrigation and water deficit conditions but not with 100-seed weight under deficit conditions. The parental genotypes and their hybrids can be used as source materials for developing genotypes with drought tolerance.
