Submitted to: Genetic Resources and Crop Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2009
Publication Date: 11/27/2009
Citation: Xie, J., Agrama, H.A., Kong, D., Zhuang, J., Hu, B., Wan, Y., Yan, W. 2009. Genetic diversity associated with conservation of endangered Dongxiang wild rice (Oryza rufipogon). Genetic Resources and Crop Evolution. 57:597-609. Interpretive Summary: Oryza rufipogon, a member of more than 20 wild species in genus Oryza, is commonly regarded as the wild progenitor of Asian cultivated rice, O. sativa, which is divided into two sub-species, indica and japonica. Dongxiang county, Jiangxi province in China is considered the northernmost place worldwide where wild rice O. rufipogon, called DXWR, has been identified. Simple sequence repeat markers were used to study conservation efficiency and genetic diversity of DXWR, and its genetic relationship with cultivated rice. The results demonstrated that conservation of the DXWR away from its original environment was less effective than it in its original environment. DXWR was genetically closer to japonica than either the male-sterile maintainer and restorer lines, or indica rice. Japonica rice has the lowest genetic diversity of cultivated rice. As a result, DXWR is a rich gene pool and is especially valuable for genetic improvement of japonica rice.
Technical Abstract: The wild progenitor species (Oryza rufipogon) of Asian cultivated rice (O. sativa) is located in Dongxiang county, China where it is considered the northernmost range worldwide. Nine ex situ and three in situ populations of the Dongxiang wild rice (DXWR) and four groups of modern cultivars were genotyped using 21 SSR markers for the study of population structure, conservation efficiency, and genetic relationships. We demonstrated that the ex situ conservation of DXWR failed to maintain its genetic identity and reduced genetic diversity. Therefore, in situ conservation is absolutely necessary to maintain the genetic identity, diversity and heterozygosity of the population. Also, in situ conservation is urgently needed because natural populations of DXWR which have decreased from nine to three, at present, due to farming activity and urban expansion. In DXWR, the three surviving in situ populations had greater genetic diversity than any cultivated rice, and were genetically closer to japonica than either the male-sterile maintainer or restorer lines, or indica rice because these O. rufipogon accessions are most closely related to japonica as compared to O. rufipogon collected anywhere else in the world.