Study On Genetic Diversity And Population Differentiation In Liaoning Weedy Rice

Weedy rice, which is also called red rice in USA, occurs in all the major rice growing areas in the tropics, even in the areas where no wild relatives of rice occur, such as the USA and Europe. With some characteristics like weed, weedy rice in the rice field will diminish farmer income both quantitatively through yield reduction, and qualitatively, through lowered commodity value at harvest. China, one of the main rice-planted countries, is facing a more and more serious rice production problem of weedy rice for the extensive use of technologies like direct seeding and simple transplant in the recent years. Liaoning province, as one of the main rice production regions in China, is also facing similar problems. In the present paper, we investigated the genetic diversity and structure of Liaoning weedy rice by the molecular markers of SSR (Simple Sequence Repeat) and RAPD (Random Amplified Polymorphic DNA). The main results are summarized as follows:1. Among 109 loci revealed by 20 RAPD primers, only primer S303 and S4 showed 4 polymorphic loci. The percent of polymorphic loci (P) was only 3.7%. The observed number of alleles (Na), effective number of alleles (Ne), Nei's gene diversity (h), shannon's information index (I) were respectively 1.0370, 1.0201, 0.011K 0.0168. Twenty-one pairs of SSR primers used in the paper revealed 10 polymorphic loci, the percent of polymorphic loci was only 47.62%. Shannon's information index and expected heterozygosity were respectively 0.2902 and 0.0393. Compared with history rice diversity research by RAPDs and SSRs, these results all showed that the genetic diversity of Liaoning weedy rice was very low.2. The Gst values measured by RAPDs and SSRs were 0.8849 and 0.6660, respectively, suggesting that about two thirds genetic variation of Liaoning weedy rice resided among populations. The AMOVA partition based on RAPDs showed that the differentiation between populations, especially between regions, was highly significant (P<0.001) with 92.31% of genetic variation resided among populations and 95.49% resided among regions. Among 10 polymorphic loci revealed by twenty-one pairs of SSR primers, four, about 40%, had specific alleles in both Shengyang and Dandong. All these showed that the differentiation between Liaoning weedy rice populations, especially between regions was quite significant.At the end of the paper, we compared the results revealed by RAPDs and SSRs and found that they showed consistent results with Liaoning weedy rice of low diversity and high differentiation. At the same time, we also found their inconsistency in the value of Gst, the diversity compared between Shengyang and Dandong and the cluster analysis of Dandong populations. These inconsistency should attributable to the low diversity revealed by SSRs and RAPDs, especially by RAPD, and the nature of these markers.