Abstract:

Littledalea przevalskyi is a member of the grass family （Poaceae） with significant ecological and economic value and with a geographic distribution including Inner Mongolia and the Qinghai-Tibetan Plateau. This research investigated the genetic diversity， genetic structure， and species distribution patterns of L. przevalskyi. The L. przevalskyi populations studied originated from 21 different regions and the genomic investigation was based on 15 pairs of simple sequence repeats （SSR） primers. A total of 147 alleles （Na） were detected by the 15 primer pairs， the average number of alleles was 9.8， the average effective allele per SSR marker （Ne） was 5.418， the average Shannon’s information index （I） was 1.808， the average expected heterozygosity （He） was 0.791， the average observed heterozygosity （Ho） was 0.882， and Nei’s gene diversity index（H） was 0.785. The polymorphism information content （PIC） of the 15 primer pairs ranged from 0.530 to 0.900 with a mean value of 0.756. The results of species level genetic diversity showed that 15 polymorphic loci were detected in the 21 populations. The average polymorphic loci was 13.57， and the average values of Na， Ne， I， He， Ho， and H were 3.299， 2.806， 1.028， 0.717， 0.841， and 0.598， respectively. The results of coefficient of genetic differentiation and gene flow quantification showed a certain degree of genetic differentiation among the L. przevalskyi populations. Analysis of molecular variance （AMOVA） revealed that 33% of total genetic variation occurred among populations， while 67% resided within populations. Integrated analysis of cluster analysis， principal component analysis （PCA）， and genetic structure analysis revealed that the genotype of samples derived from different distribution areas had significant differences. Based on the geographical origins of the samples， the 21 population samples can be roughly classified into two subgroups， the southeastern populations （subgroup I） primarily consisting of originating from Maduo， Maqin， southeastern Qumalai， Yushu， and Riwoqê， and the northwestern populations （subgroup Ⅱ） mainly including those originating from Geermu， northwestern Qumalai， and Chenduo. A Mantel test showed there was a significant correlation between genetic distance and geographical distance （r=0.412； P<0.001）， implying the genetic differentiation among different populations may be related to geographical barriers. The results of this study provide a theoretical and quantitative basis for exploring and categorizing the phylogenetic relationships， species definition， germplasm resource evaluation， and conservation and utilization of wild resources of the genus Littledalea.

Key words: Littledalea przevalskyi, simple sequence repeats （SSR） molecular marker, genetic diversity, genetic structure