Phylogenetic relationships among diploid species of Oryza officinalis complex revealed by multiple gene sequences
利用多基因序列探讨稻属药稻复合体二倍体物种的系统发育关系

Oryza officinalis complex includes five diploid species involving the B, C and E genomes, and is distributed in Asia, Africa and Oceania. These species are very important because O. australiensis is the only species with E genome, while O. punctata is the single species with B genome. Although there are three species with the C genome (O. eichingeri, O. officinalis and O. rhizomatis), these species might have played different roles in speciation of polylploids due to their disjunction in Asia and Africa. The phylogenetic relationships among these diploids are still unclear, and polyploidy speciation involving these diploids has long been in debate. In this study, we utilized the sequence data of multiple genes, including the chloroplast matK, internal transcribed spacer (ITS) fragment of nuclear ribosomal DNA, and two nuclear genes (Adh1 and Adh2), to infer the phylogenetic relationships among the diploids and the related genomes. The separate and combined analyses were implemented by both maximum parsimony and maximum likelihood methods. The results indicate that (1) the C genome showed a closer affinity to the B genome than to the E genome; (2) of the three species with the C genome, O. officinalis and O. rhizomatis showed a closer relationship to each other than to O. eichingeri; (3) notably, in O. eichingeri, there exists higher divergence between the samples from Africa and those from Sri Lanka although they formed one monophyletic clade with lower bootstrap support.