Implications of additive x additive epistasis for common bean breeding

Abstract

The presence of epistasis in complex traits can be significant and affect the selection of segregating populations undesirably. The purpose of this study was to determine the epistatic genetic components that influence root and shoot traits of common bean and identify their effect on the performance of segregating populations. The field experiment consisted of 49 treatments (backcross progenies, parents and segregating populations in the F2 and F3 generations). The cross P1-BAF53 (Andean) x P2-IPR 88 Uirapuru (Mesoamerican) as reference. Six traits were taken into consideration: root distribution (%), first pod length (cm), number of grains (plot), plant height (cm), reproductive cycle (days) and number of basal branches (plot). Additive x additive epistasis significantly affected 50% of the above traits. For root distribution (RD), this genetic component deteriorated the mean performance of the progenies in relation to the parents, regardless of the presence of dominance deviations and additive x dominant and dominant x dominant epistasis. In addition, lower variation in the different generations (parents and F2 and F3 progenies) was found for RD than for the other traits. Rather, no additive x additive interaction component for plant height was detected, but predominance of genetic deviations of dominance and transgressive segregation events were identified. Thus, additive x additive epistasis can hamper the success of a breeding program, for being associated with low-variability traits. This fact may be related with the number of crosses and/or the choice of genetically more distant parents for the program, and possibly with the presence of linked genes.