Genetic Diversity Of Natural Populations Of Rosa Laxa Retz. And Rosa Platyacantha Schrenk In Tianshan Mountains Of Xinjiang

Rosa laxa Retz. and Rosa platyacantha Schrenk are native species widely disturbuted in Xinjiang Uigur Autonomous Region of China. Due to the complex climate and geography in Xinjiang, these two wild rose species are excellently resistant germplasms for modern roses breeding. However, few studies had been carried out in the two species, as well as their applications. It is very necessary to study the genetic diversity of the wild populations, the genetic variation within or among populations, patterns and factors of genetic differentiation of the two wild species, which should be benefical for their futher research and utilization.In order to solve the issues above, natural populations of R. laxa and R. platyacantha were investigated in Tianshan Mountains of Xinjiang from 2007 to 2009. Each 6 natural populations of R. laxa and R. platyacantha were selected to analysis the genetic diversity by phenotype traits and AFLP molecular markers. The main results were as follows:1. R. laxa and R. platyacantha were widely distributed in the valleys, hills, forest edge, dry river bed or canal side in Tianshan Mountains. The altitudes of R. laxa were ranged from 500 to 1700 metres above sea level (asl.) while the altitudes of R. platyacantha were from 500 to 2400 meters asl. R. laxa and R. platyacantha, which had been applied as good ornamentals in local regions, were clarified with wide adaptability and the resistances for cold and drought. Moreover, both species played a great significant role for maintaining the local ecological environment and biodiversity.2. The results of phenotypic diversity analysis were listed as follows: There were significant differences in the phenotypic traits among populations and among individuals within populations of R. laxa and R. platyacantha. The mean phenotypic differentiation coefficient(VST) of the morphological traits among populations of R. laxa and R. platyacantha was 41.84% and 27.50% respectively, indicating the similar abundance in phenotypic diversity among and within populations of R. laxa while more abundances in phenotypic diversity within populations than those among populations of R. platyacantha. The average variation coefficient (CV) of phenotype traits of R. laxa and R. platyacantha was 22.79% and 16.51%. The mean phenotypic differentiation coefficient (VST) and the average variation coefficient (CV) of R. platyacantha were all smaller than that of R. laxa, which indicated that R. laxa were more abundant in phenotypic diversity than R. platyacantha. Duncan's test of CV and the principal component analysis of phenotypic traits both indicated that the traits on inflorescences and seeds of R. laxa and the traits of seeds of R. platyacantha were the main factors account for the phenotypic variations respectively. The correlation analysis showed that there was no significant correlation between the phenotypic traits of the two spieces and geographic factors. According to the UPGMA clustering analysis, the 6 populations of R. Laxa, as well as the 6 populations of R. platyacantha in this study could be both divided into three groups. These clustering results showed that the groupings of both species were not due to geographic distances, but related to the niches of R. Laxa or the altitudes of R. platyacantha respectively.3. The results of AFLP analysis of genetic diversity showed that: Percentage of polymorphic loci of R. laxa and R. platyacantha were 54.06% and 63.96%. Nei's genetic diversity indexs (h) were 0.288 and 0.2564, Shannon information indexs (I) were 0.3073 and 0.3796, coefficients of gene differentiation of were 0.3236 and 0.081, gene flows (Nm) were 1.0451 and 5.6766 respectively. Compared to these genetic parameters of R. laxa and R. platyacantha, Nei's genetic diversity index, the total population gene diversity (Ht), genetic diversity among populations (Dst) and coefficient of gene differentiation (Gst) of R. platyacantha were smaller than those of R. laxa, genetic diversity within populations (Hs) and gene flow (Nm) of R. platyacantha were bigger than those of R. laxa, indicating the genetic diversity and genetic differentiation among populations of R. laxa were abundant than those of R. platyacantha. The genetic diversity within populations of the two species was both abundant than those among populations. Nei's genetic identity coefficient of R. laxa and R. platyacantha were 0.862 and 0.967 respectively. According to the UPGMA clustering analysis by Nei's genetic distance, the 6 populations of R. Laxa, as well as the 6 populations of R. platyacantha in this study could be both divided into three groups with geographic distances, which were very different with the results of phenotype traits analysis.4. It can be concluded from the anlysis of phenotypic traits and AFLP molecular markers that the genetic diversity of R. laxa was more abundant than that of R. platyacantha. The genetic diversity of R. laxa was both abundant within populations and among populations, but the genetic diversity within populations of R. platyacantha were more significantly abundant than the genetic diversity among populations.