Analysis of Genetic Variation, Correlation and Path Effects for Grain Yield Enhancement in Bread Wheat (Triticum aestivum L.) under Rainfed and Irrigated Conditions

Abstract

Drought constrains wheat productivity, making the identification of genetically variable and yield-associated traits important for selection under contrasting moisture regimes. This study evaluated 50 advanced bread wheat genotypes, including five standard checks, under rainfed and irrigated environments during the Rabi season of 2022–23 using a randomised block design with three replications. Two physiological and fourteen yield-related morphological traits were assessed using analysis of variance, phenotypic and genotypic coefficients of variation, broad-sense heritability, genetic advance, correlation, and path coefficient analyses. The phenotypic coefficient of variation exceeded the genotypic coefficient of variation for all traits in both environments. Canopy temperature depression at 14 days after heading (CTD 2) showed the highest PCV/GCV values, at 39.90/33.42% under rainfed and 34.26/29.45% under irrigated conditions. Productive tillers per plant and CTD 2 combined high heritability with comparatively large genetic advance in both environments. Under rainfed conditions, grain yield per plot was strongly and positively correlated with harvest index (r = 0.721), productive tillers per plant (r = 0.698), and biological yield per plot (r = 0.626). Under irrigation, the strongest positive associations were with peduncle length (r = 0.611), spike length (r = 0.606), flag leaf length (r = 0.563), and biological yield per plot (r = 0.552). Path analysis identified harvest index as the largest positive direct contributor under rainfed conditions (0.8029) and biological yield per plot under irrigated conditions (0.8620). These findings support consideration of these traits in selection across contrasting moisture regimes.