Genetic Variability, Broad-Sense Heritability, and Trait Associations of Bread Wheat (Triticum aestivum L.) Across Multiple Environments in Kenya
Ego Amos Kibiwott *
Department of Biotechnology, University of Eldoret, P. O. Box 1125–30100, Eldoret, Kenya.
Kinyua Miriam Gacieri
Department of Biotechnology, University of Eldoret, P. O. Box 1125–30100, Eldoret, Kenya.
Kiplagat Oliver Kipchoge
Department of Biotechnology, University of Eldoret, P. O. Box 1125–30100, Eldoret, Kenya.
*Author to whom correspondence should be addressed.
Abstract
Aims: This study evaluated phenotypic variation and genotypic differences, estimated broad-sense heritability for grain yield, and examined associations among agronomic traits in five bread wheat (Triticum aestivum L.) genotypes comprising two parental cultivars and three mutation-derived lines.
Study Design: Randomised complete block design with three replications.
Place and Duration of Study: The genotypes were evaluated at Kitale, Eldoret, and Njoro, Kenya, during the 2021 and 2022 long-rain seasons, representing six environments.
Methodology: Seven agronomic traits were analysed using descriptive statistics, combined analysis of variance, restricted maximum likelihood estimation of variance components, entry-mean broad-sense heritability, and Pearson correlation analysis.
Results: Grain yield ranged from 1.80 to 3.50 t ha⁻¹, with a mean of 2.70 t ha⁻¹. Genotype significantly affected all evaluated traits, demonstrating differentiation among the wheat materials, while environmental effects varied among traits. Grain yield was significantly influenced by genotype, location, and season, with a significant genotype × location interaction indicating differential genotypic responses across locations. For grain yield, genotypic variance (σ²G = 0.018) exceeded residual variance (σ²e = 0.012) and genotype × environment interaction variance (σ²GE = 0.006). Entry-mean broad-sense heritability was high (H² = 0.91), indicating strong repeatability of differences among genotype means under the multi-environment testing framework. Grain yield was moderately and positively associated with thousand-kernel weight (r = 0.42), while days to maturity was moderately and negatively associated with thousand-kernel weight (r = −0.53). Days to heading and days to maturity were moderately and positively correlated (r = 0.42).
Conclusion: The relatively large genotypic variance and high entry-mean heritability indicate that the evaluated materials could be reliably differentiated for grain yield across the testing framework, although environmental and interaction effects remained relevant. Integrating replicated grain-yield performance with genetic parameters and complementary agronomic traits, particularly thousand-kernel weight, provides a sound basis for identifying promising parental and mutation-derived materials for advancement in bread wheat improvement.
Keywords: Bread wheat, broad-sense heritability, genetic variability, genotype × environment interaction, multi-environment evaluation, trait associations