Study On The Origin And Evolution Of Oryza Sativa Based On Ene Diversity Of Mitochondrial Genomes

As an important food crop, rice is the staple food for more than half of the World’s population.However, as improvement by modern breeding and biotechnology, the genetic background of new ricevarieties becomes more and more narrow, and directly hinders the process of rice breeding. Tobreakthrough this situation, scientists in China and even in the World began to focus on screen superiorgenetic resources from wild rice (Oryza rufipogon) which has been recognized to be the ancestor ofAsian cultivated rice. Because of adapting to the environment and changing climate, wild rice hasaccumulated aboundant genetic diversity and contains lots of superior genes that Asian cultivated ricedoes not contain or has lost. To meet above reguirements, it is significant to have the knowledge such aswhere cultivated rice originated from and how it was domesticated and therefore to provide scientificreference for parents selection for rice breeders.In this study,386accessions from Oryza rufipogon and Asian cultivated rice were collected fromChina, East Asia, South Asia and Southeast Asia, and5genes, cox3, cox1, orf224, ssv-39/178,rps2-trnfM in mitochondrial genome of rice, were sequenced. Through the study of the gene diversity ofthe five genes to explore the origins of Asian cultivated rice, we verified the following propositions：1. The mitochondrial genetic diversity of common wild rice is higher than the Asian cultivated rice,and the mitochondrial genetic diversity of indica higher than japonica. In this study there are4553sitesin the whole study sequence which have286InDels and75SNPs, accounting for1.65%and6.28%ofthe whole sequence, respectively.2. From the genetic diversity of common wild rice and the two subspecies of cultivated rice, indicaand japonica, we discovered that there is a parallel evolutionary relationship between indica andjaponica, and the indica-japonica differentiation corresponds the Secondary Theory of the origin, inanother word, common wild rice exists the indica-like and japonica-like types, and the two subspecieswere evoluted from the indica-like wild rice and the japonica-like wild rice respectively.3. To study the evolutionary and origin of Asian cultivated rice, we found that japonica riceoriginated in Southern China, and then spreaded from this area to other regions. Indica rice mightoriginate in either Southern China or India, and then spreaded to other regions incluiding China andIndia, but some genes exchange occured in Southeast Asia. The results could also infer that indica ricemight originate in Southern China and Southeast Asia, and then spreaded from the originated areas toother regions. So we concluded that China is one of the origins of Asian cultivated rice, and supportSouthern China origin theory.The results also indicated that the mitochondrial genome evolutes very slowly, butit still could beutilized to study the origin and the pathways of evolution with screening the objective genes.Furthermore, we could conclude that this study made clear that China is one of the origin regions ofcultivated rice and japonica subspecies and indica species of cultivated rice were originated fromcommon wild rice respectively, which could provide scientific support for rice breeders to select parentsto do rice breeding.