Comparisons of microsatellite variability and population genetic structure of two endangered wild rice species, <Emphasis Type="Italic">Oryza rufipogon</Emphasis> and <Emphasis Type="Italic">O. officinalis</Emphasis>, and their conservation implications

Conserving endangered wild rice species requires a thorough understanding of their population genetic structure and appropriate approaches. We applied six and seven microsatellite loci to study the genetic structure of six populations throughout the range of Chinese Oryza rufipogon and Oryza officinalis, respectively. The results showed that O. rufipogon possesses higher levels of genetic diversity but lower differentiation (R_S = 3.2713, P = 100.0%, H_O = 0.1401, H_S = 0.5800, F_ST = 0.271) than O. officinalis (R_S = 2.0545, P = 57.14%, H_O = 0.0470, H_S = 0.2830, F_ST = 0.554). Mean population F_IS was slightly larger for O. officinalis (F_IS = 0.844) than that for O. rufipogon (F_IS = 0.755), indicating that O. officinalis has slightly higher departures from Hardy–Weinberg expectations and heterozygosity deficits than O. rufipogon. In addition to different origins and evolutionary histories, O. officinalis has restricted gene flow, high inbreeding, isolated small populations and fewer opportunities of hybridization with other taxa, which may determine major differences in population genetic structure from O. rufipogon. Our results suggest the adoption of a plan of involving fewer populations but more individuals within populations for O. rufipogon, while both the number of populations and the individuals for a sampled population should be almost equally considered for O. officinalis. The known high degree of inbreeding in the populations of both species implies that conservation and restoration genetics should particularly focus on the maintenance of historically significant processes such as high levels of outbreeding, gene flow and large effective population sizes. We finally proposed to further estimate the role of rice gene flow in the conservation of O. rufipogon, and to perform detailed analysis of mating systems in both species for better conservation perspectives of their ecological and evolutionary processes.