Evidence for selection events during domestication by extensive mitochondrial genome analysis between japonica and indica in cultivated rice.

The history of the domestication of rice is controversial, as it remains unknown whether domestication processes occurred once or multiple times. To date, genetic architecture and phylogenetic studies based on the rice nuclear genome have been extensively studied, but the results are quite different. Here, we found interesting results for different selections in Oryza sativa based on comprehensive studies of the rice mitochondrial (mt) genome. In detail, 412 rice germplasms were collected from around the world for variant architecture studies. A total of 10632 variants were detected in the mt genome, including 7277 SNPs and 3355 InDels. Selection signal (π/π) indicated that the selection sites in Oryza sativa L. ssp. japonica were different from those of Oryza sativa L. indica rice. The fixation index (F) was higher between indica and japonica than between indica and wild rice. Moreover, haplotype and phylogenetic analyses also revealed indica clusters and japonica clusters that were well separated from wild rice. As mentioned above, our studies indicate that the selection sites of the indica type were different from those of the japonica type. This means that indica and japonica have experienced different domestication processes. We also found that japonica may have experienced a bottleneck event during domestication.