Population structural analysis of an in-situ conservation site for wild rice in Laos.

An in-situ conservation site in Laos for a mixture of annual and perennial wild rice, LV27, which is a single swamp with an observation pier has been developed. In order to develop a strategy for evaluation of natural resources, systematic leaf sampling has been conducted and their genetic characteristics measured with 16 SSR loci. In order to determine population structure, a small number of individuals localized together were regarded as sub-populations belonging to a single mother population. Annual individuals were clustered at particular peripheral areas of the pond. Perennial individuals were close by and growing within deeper pond water. Scores of observed heterozygosity (Ho) were not significantly different between annual and perennial sub-populations, but relatively lower in annual ones. Genetic distance among annual and perennial sub-populations in close juxtaposition at peripheral sites showed that annuals were clustered against perennials. In addition, comparison of perennial sub-populations peripheral areas and inside the swamp, found they clustered together and were some distance from annual ones. When the genetic components were compared in detail, private alleles were frequently found in annual plants, suggesting there might be restriction of gene flow between annual and perennial types. Partitions of deep water perennial sub-populations identified private alleles in particular areas, suggesting there were some areas with unique polymorphisms. Combining peripheral perennial sub-populations led to the disappearance of most private alleles which implied there is frequent gene flow among perennial sub-populations. This in-situ conservation site allowed us to observe the succession of populations and also to research detailed population structure of a typical wild population and this found wild rice genetic structure in this single swamp is complex. The data obtained will provide valuable insight about how to evaluate wild populations genetically and how to deal with such populations as field collections.