Yohei Koide, Mitsunobu Ikenaga, Noriko Sawamura, Daisuke Nishimoto, Kazuki Matsubara, Kazumitsu Onishi, Akira Kanazawa, and Yoshio Sano

摘要

Transmission ratio distortion (TRD) is frequently observed in inter- and intraspecific hybrids of plants,nleading to a violation of Mendelian inheritance. Sex-independent TRD (siTRD) was detected in a hybridnbetween Asian cultivated rice and its wild ancestor. Here we examined how siTRD caused by an allelicninteraction at a specific locus arose in Asian rice species. The siTRD is controlled by the S6 locus via anmechanism in which the S6 allele acts as a gamete eliminator, and both the male and female gametesnpossessing the opposite allele (S6na) are aborted only in heterozygotes (S6/S6na). Fine mapping revealed thatnthe S6 locus is located near the centromere of chromosome 6. Testcross experiments using near-isogenicnlines (NILs) carrying either the S6 or S6na alleles revealed that Asian rice strains frequently harbor annadditional allele (S6nn) the presence of which, in heterozygotic states (S6/S6nn and S6na/S6nn), does not result innsiTRD. A prominent reduction in the nucleotide diversity of S6 or S6na carriers relative to that of S6nn carriersnwas detected in the chromosomal region. These results suggest that the two incompatible alleles (S6 and S6na)narose independently from S6nn and established genetically discontinuous relationships between limitednconstituents of the Asian rice population.