Contribution of Secondary Traits for High Grain Yield and Stability of Tropical Maize Germplasm across Drought Stress and Non‐Stress Conditions
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Information is needed on the contribution of secondary traits to grain yield and stability in maize (Zea mays L.). This study aimed at identifying stable and high yielding hybrids as well as traits contributing to high yield and stability in tropical maize. Twentytwo test hybrids and six check hybrids were evaluated under five environments in Karnataka, India, using a 4 x 7 alpha-lattice design with two replications. Genotype main effect plus genotype x environment interaction biplot model was used to ascertain genotype stability and yield across environments. Genotype x trait biplot, t test, and step-wise regression analyses were used to determine trait expression differences between high yielding and stable, and low yielding and unstable hybrids. Genotypic correlations and heritability were used to estimate correlated response to selection for grain yield via each secondary trait. Mean grain yield under drought was 20% of that across environments, thus selection in both drought and non-drought stress environments is required. Hybrids GH-12444 and GH-12408 were high yielding and stable across environments, and should be tested widely. Some traits, such as tassel size, had correlated response to selection values of near unity making them unsuitable for indirect selection. However, such traits could be used to supplement selection for grain yield given their high heritability and that they are relatively easy to measure. Different traits were associated with grain yield under different conditions thus suggesting that both drought and nondrought stress conditions must be used as selection environments using secondary traits specific to a given environment.
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