Breeding Effects on Grain Filling Traits in Moroccan Durum Wheats Grown Under Contrasting Environments

Yield crops is a complex component depending on several grain filling traits. Knowledge of their relative contribution to grain yield determination under contrasting environments is essential to optimize grain yield and its stability. This study evaluates the changes resulting from durum wheat breeding in Morocco during the last three decades on grain filling rate (R) and duration (D), final grain weight (W), and days from sowing to anthesis (DSA). A set of six durum wheat varieties, released between 1984 and 2007, was grown in experiments conducted under contrasting environments during three growing seasons. The analysis of variance revealed that water regimes and growing seasons accounted for the largest percentages of variability for R, D, W, and DSA. D and DSA increased significantly over time under both water regimes. W exhibited an increasing trend under irrigated conditions, but a significant decline under rainfed ones. In contrast, the change of R was only significant under irrigated conditions. The path coefficient revealed that irrigated and rainfed conditions impacted differently the direct and indirect effects among traits with higher values of direct effects recorded under water-limited conditions. Within irrigated trials, R and D affected directly and positively grain yield. Regarding rainfed conditions, grain yield was only dependent on W. These findings indicate that genetic progress in grain filling traits and their direct and indirect effects on grain yield differed significantly between rainfed and irrigated conditions. Therefore, when selecting for high-yielding durum wheat genotypes, a particular attention should be paid to the environmental conditions.