| Leymus chinensis is an important perennial grass species that is widely distributed in the typical grassland communities of the Eurasian steppe region.It is a high quality and nutritionally valuable forage crop that is relished by livestock.Studies on genetic diversity are important in plant breeding for the successful exploitation of plants?genetics to breed and grow new improved varieties.Some researchers use morphological characterization methods to study plant diversity but this is usually time consuming.In contrast,germplasm collection is a means of preserving a cultivated species genetic diversity to prevent the loss of this biological value during the implementation of monoculture systems for high input crops.Germplasm–the sum total of hereditary materials–including all the alleles of the various genes present in a crop species and its wild relatives–could be studied for crop improvement.Leymus chinensis has recently received considerable attention on its genetic diversity.But genetic diversity studies on L.Chinensis using SSR markers is currently limited.In the present study nineteen SSR markers were used to study genetic diversity across 166 L.Chinensis individuals.Additionally,10morphological and physiological indicators were evaluated including leaf length,leaf width,leaf number,leaf weight,leaf area,node numbers,plant height,SPAD Chlorophyll,stem weight,yield.The findings revealed that mean values for the parameters are leaf length 11.124 cm,leaf width 0.451cm,leaf number 2.810,leaf Weight 0.145g,leaf area 1.304 cm~2,node number 2.735,plant height 58.556cm,SPAD Chlorophyll 44.397,stem weight 0.829 g,and the mean yield was 0.947 kg/m~2.In additionuy higher mean values for the parameters were observed for plant height 58.556 cm,SPAD Chlorophyll44.397,and leaf length 11.124 cm,whereas,lower mean values were observed for leaf weight 0.145g and leaf width 0.451 cm.Correlation analysis was performed on 10 quantitative traits of Leymus chinensis germplasm and the results showed significant difference among the traits.Principal component analysis was conducted to assess the phenotypic variation of L.Chinensis germplasm.The five principal components(PCs)extracted had eigenvalues>1 and contributed 85.20%of the variation among the Leymus chinensis germplasm.PC1,PC2,PC3 PC4 and PC5 cumulatively accounted for39.984%,58.268%,70.092%,78.331%and 85.200%variation,respectively.Cluster analysis was carried out using the unweighted paired group method and the arithmetic average showed the distinct pattern of group formation.The mean performances of 10 characters in five clusters was studied.Most of the characters showed a distinct difference between the clusters.Moreover,nineteen SSR primers were used for genetic diversity and a total of 133 alleles were detected across the 166 L.Chinensis plants.The polymorphic rate was more than 80%for all SSR markers,except SSR12i and SSR6c which showed 50%and 75%polymorphism,respectively.Remarkably,SSR7d,SSR8e,SSR9f,SSR10g,SSR11h,SSR17n,SSR19r,SSR20s,SSR22t,SSR24u and SSR25v showed the highest polymorphic rate of 100%.In addition,the number of bands ranged between 4 and 10,while polymorphic bands were between 2 to 10.The gene diversity(H)ranged from0.0545 for SSR12i to 0.4720 for SSR25v,and the average was 0.3136.The effective number of alleles(Ne)ranged from 1.0600 for SSR12i to 1.8990 for SSR25v with an average of 1.5199.Moreover,the Shannon?s information index(I)ranged from 0.1203 for SSR12i to 0.6646 for SSR25v with an average of 0.4761.Genetic diversity analysis showed that the 166 samples could be classified into five main population clusters based on their maximum membership coefficients which was designated as Pop1 to Pop5.Neighbor-joining(NJ)phylogenetic analysis and principal component analysis(PCA)were used to detect the genetic relationship among the 166 L.chinensis individuals based on the Manhattan index dissimilarity matrix.Both the NJ dendrogram tree and the PCA plot clearly distinguished 5 clusters.In addition,the x-and y-axis in the PCA plot explained 5.72%and 4.86%variance within the molecular data.Among the five populations,the largest values of allele(total number of detected alleles),Na(observed mean number of alleles),and Ne(effective number of alleles)was found to be higher in Pop1,which were 61,1.977,and 1.461,respectively.Additionally,both analysis of molecular variance(AMOVA)and pairwise Fst fixation index analysis were performed to investigate the genetic variation among these populations.The AMOVA results showed that 13%of the total genetic variation occurred among the population and 87%genetic variation within the populations of the species.Moreover,moderate genetic differentiation was indicated by pairwise Fst ranging from 0.0336 to 0.0731.The highest level of genetic difference was between Pop2 and Pop4,whereas the lowest appeared between Pop1 and Pop3.Finally,the principal coordinate analysis(PCA)was carried out using the Gen Al Ex version 6.5 based on the matrix of pairwise Nei?s unbiased genetic distance.The results showed that5.72%of the variance within the molecular data was illustrated by the x-axis,and 4.86%explained by the y-axis.Taken together,these SSR markers provide new insight for a relatively accurate understanding of the genetic diversity of L.Chinensis germplasm and could potentially enhance the breeding,propagation and application of Leymus Chinensis. |
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