Assessment of genetic diversity and genetic structure of wild rice populations in Myanmar

To evaluate genetic diversity and genetic structure of wild rice (Oryza rufipogon) populations in Myanmar, seven research sites were selected based on various ecological conditions. A large number of samples under natural growth conditions were collected and studied using six simple sequence repeats (SSRs) and two chloroplast DNA markers. A total of 77 alleles were detected from 1559 samples over six SSR loci. The mean number of alleles per population ranged from 3.167 to 8.667, and the mean expected heterozygosity ranged from 0.140 to 0.701. Wild rice populations survived under various environmental conditions and retained different levels of genetic diversity. The large number of samples was effective to confirm the spatial genetic structure of wild rice populations in a relatively small area. Regarding chloroplast DNA polymorphisms, four populations possessed only one pattern, while the other three showed two or five combinations of haplotypes, even within the same population. Additionally, the existence of a new genotype was revealed. Considerable variations in chloroplast DNA exist in the wild rice populations of Myanmar. A high proportion of genetic variation was detected within, rather than among, populations. To ensure maintenance of allelic diversity, it is advisable to preserve many individuals from a large population.