Boron (B) is a crucial micronutrient, particularly in volcanic soils where its deficiency hampers agriculture. Here, we investigate the genetic basis of leaf B accumulation in natural populations of Arabidopsis thaliana that colonized volcanic islands in Cape Verde. Using a combination of genome-wide association studies (GWAS) and mapping in a recombinant intercross population, we identified a case of convergent phenotypic evolution in which multiple variants in the two principal B transporter genes, BOR1 and BOR2 , increase leaf B accumulation in parallel. These include multiple tandem duplications at BOR1 that arose independently in different populations. Overall, this study reveals a remarkable case of convergent evolution occurring within a relatively short time scale, where different types of de novo mutations at B efflux transporter genes achieve similar phenotypic outcomes. Further, our findings show that integrating recombinant populations with GWAS in natural populations can improve power to overcome allelic heterogeneity.
Tergemina et al. (Mon,) studied this question.