Chloroplast phylogeography of AA genome rice species

Abstract

Whole chloroplast genome sequence analysis of 58 wild and domesticated rice samples was used to investigate their phylogeny providing more detail on the biogeography of the major groups of wild A genome rices globally. An optimized chloroplast assembly method was developed and applied to extracting high quality whole chloroplast genome sequences from shot gun whole DNA sequencing data. Forty complete high quality chloroplast genome sequences were assembled (including; temperate japonica, tropical japonica and aus). South American, African wild rice relationship were conformed, while the Australian chloroplast type was found to extend north to the Philippines. The remainder could be divided into an African (O. barthii and the domesticated O. glaberrima) clade and the Asian taxa. The Asian taxa was placed in two distinct clades including the domesticated O. sativa ssp. indica and O. sativa ssp. japonica respectively. These two groups of wild rices had substantially overlapping distributions with the O. sativa japonica group extending further west into India. The aromatic rices had japonica chloroplasts as expected. A polyphyletic maternal genome origin of the cultivated aus group of rices was suggested by the identification of aus accessions in both the indica and japonica clades. The current distribution of the chloroplast types appears to differ significantly to that of the nuclear genome diversity suggesting a complex evolutionary history of the rice progenitors leading to the domestication of rice.