Genotype-by-Environment Interaction in Interspecific \u3cem\u3eUrochloa\u3c/em\u3e Hybrids Using Factor Analytic Models

Environmental factors can influence plant phenotypes shaping the expression of pastures. The ability to test genotypes in multiple environments is critical in a breeding program because important traits are heavily influenced by the environment. Nutritional quality is critical in forage breeding because it affects the rate of live weight gain in livestock as well as the quality of end products such as milk and meat. However, there is not much information on the environmental effect on agronomic and nutritional quality traits in tropical forages. For this reason, the objective of the present study was to investigate the genotype-by-environment interaction in a breeding population of interspecific Urochloa hybrids evaluated for agronomic and nutritional quality traits across four locations in Colombia, using factor analytic mixed models. Phenotypic correlations among traits ranged from 0.26 (plant area vs dry weight) to 0.93 (fresh weight vs dry weight), indicating a strong interaction in some traits. Genetic correlations among environments showed different ranges depending on the variable evaluated. For example, plant height genetic correlations among environments ranged from 0.16 to 0.9, indicating high genotype-byenvironment interaction. The factor analytic analysis revealed that two factors explained more than 60% of the genetic variance in all traits evaluated and that 80% of the environments were clustered in the first factor. Factor analytic biplot indicates that Llanos location differed strongly from other locations evaluated. Based on the results obtained, the factor analytic analysis is a useful tool to stratify environments and identify Urochloa cultivars adapted to different ecological niches