Detecting directional epistasis and dominance from cross-line analyses in alpine populations ofArabidopsis thaliana

Abstract

AbstractThe contribution of non-additive genetic effects to the genetic architecture of fitness, and to the evolutionary potential of populations, has been a topic of theoretical and empirical interest for a long time. Yet, the empirical study of these effects in natural populations remains scarce, perhaps because measuring dominance and epistasis relies heavily on experimental line crosses. In this study, we explored the contribution of dominance and epistasis in natural alpine populations ofArabidopsis thaliana, for two fitness traits, the dry biomass and the estimated number of siliques, measured in a greenhouse. We first found that, on average, crosses between inbred lines ofA. thalianaled to mid-parent heterosis for the dry biomass, but outbreeding depression for the estimated number of siliques. While heterosis for the dry biomass was due to dominance, we found that outbreeding depression for the estimated number of siliques could be attributed to the breakdown of beneficial epistatic interactions. We simulated and discussed the implication of these results for the adaptive potential of the studied populations, as well as the use of line-cross analyses to detect non-additive genetic effects.