Genotype and environmental effects on grain yield and thousand-grain weight of bread wheat genotypes in Zimbabwe

Abstract

Wheat (Triticum aestivum L.) production in Zimbabwe is largely dependent on irrigated winter systems, yet the performance of advanced wheat lines may differ across production environments because of variation in soil type, altitude, temperature, irrigation regime and field conditions. The objective of this study was to evaluate the effects of genotype, environment, and their interaction on grain yield and thousand-grain weight (TGW) of bread wheat genotyps across four environments in Zimbabwe. The evaluation set consisted of 20 bread wheat genotypes, comprising 14 CIMMYT-derived elite lines and six commercial checks, which were field evaluated at Mount Hampden (MHD), Manhundu Farm, Mazowe (MuFM), Suffolk Farm, Musami (SFM) and Machiri Farm, Mazowe (MaFM) during the 2024 winter cropping season. The experiment was laid out using an alpha-lattice design with three replications at each location. Combined analysis of variance showed highly significant (P < 0.001) effects of environment and G × E interaction for grain yield; whereas the genotype main effect was not significant (P > 0.05). Environment, genotype and G × E interaction accounted for 44.4, 3.6 and 13.5% of the total grain-yield variation, respectively. Across locations, CIMMYT-derived genotypes, E13, E11 and E10 and commercial checks W3 and W5, recorded the highest numerical mean grain yields. However, these differences were not significant in the combined analysis and should be treated as candidates for further location-specific testing, rather than as broadly superior genotypes. For TGW, genotype and environment effects were significant; whereas the G × E interaction was not significant, indicating more consistent genotypic expression across environments. Genotypes E14, E1, E3 and E10 recorded the highest mean TGW, with E14 and E1 showing favourable mean performance and stability patterns. The results show that grain yield is dominated by environment-specific responses; while TGW provided clearer evidence for selecting grain-weight donors. Further evaluation across multiple seasons, additional locations and industrial grain-quality traits is required before firm cultivar recommendations can be made.