Heterosis for the root distribution trait in common bean

ABSTRACT. Heterosis has been one of the most studied phenomena since genetic studies were conceived. Knowledge of this phenomenon for the root distribution trait in beans (Phaseolus vulgaris L.) can favour the development of genotypes that are more tolerant to abiotic stresses. This study aimed to verify the occurrence of heterosis for the root distribution trait in hybrid F1 populations of common bean derived from crosses within and between gene groups. Thirty-six populations (six parents and 30 hybrids) were evaluated under field conditions in the agricultural years 2016/17 and 2017/18. The root distribution was assessed with the adapted Bohm method. The genotypes responded similarly to environmental changes (absence of an interaction). However, the root distribution differed significantly between the agricultural years. Comparisons between the mean of hybrids from crosses within each gene pool and the mean of parents did not reveal heterosis. The comparisons between gene groups showed significant differences only between BRS Embaixador x IPR Uirapuru, CBS 14 x IPR Uirapuru, and BAF 53 x IPR Uirapuru and the mean of parents. The absence of heterosis in the root trait can be explained by the degree of kinship between the gene groups, as well as some epistatic interactions.