Capsicum annuum with causal allele of hybrid weakness is prevalent in Asia.

Reproductive isolation, including hybrid weakness, plays an important role in the formation of species. Hybrid weakness in Capsicum, the cessation of plant growth, is caused by two complementary dominant genes, A from C. chinense or C. frutescens and B from C. annuum. In the present study, we surveyed whether 94 C. annuum accessions had B or b alleles by crossing with C. chinense having the A allele. Of the 94 C. annuum accessions, five had the B allele, three of which were native to Latin America and two were native to Asia. When combined with previous studies, the percentage of B carriers was 41% in Japan, 13% in Asia excluding Japan, 6% in Latin America, and 0% in Europe and Africa. In addition, 48 accessions of C. annuum from various countries were subjected to SSR analysis. Clades with high percentages of B-carriers were formed in the phylogenetic trees. In the principal coordinate analysis, most B-carriers were localized in a single group, although the group also included b-carriers. Based on these results, we presumed that the B allele was acquired in some C. annuum lines in Latin America, and B-carriers were introduced to the world during the Age of Discovery, as along with the b-carriers.