Analysis Of Genetic Diversity And Population Structure On Alfalfa Germplasms

Alfalfa(Medicago sativa L.), as one of the most important legume forage, can both ameliorate soil and increase the content of high quality protein in forage. It’s the physical basis of high quality and efficient graziery development. Hence, to develop alfalfa germplasm resources and study the genetic diversity and genetic relationship among populations are of great importance to the genetic improvement of alfalfa varieties in theory and practice. We investigated yield traits, genetic diversities and population structure of77alfalfa materials, our results are as follows:1. Yield traits characteristics analysis of77alfalfa materials demonstrated that the genetic variation among the tested alfalfa varieties (families) showed extremely diversity. The genetic variation between different varieties (families) is greater than that inner varieties (families). We can conclude from the tested alfalfa varieties (families) that five yield traits showed various variations. The coefficient of variation ranked as grass yield> hay yield> number of branches> cutting height> growth rate> fresh-dry ratio, The maximum average coefficient of variation for fresh yield is23.53, while the minimum average coefficient of variation for fresh and dry ratio is11.11. The variation of alfalfa varieties is more stable than the alfalfa family.2. Correlation analysis of five yield traits indicated that the correlation coefficient of grass yield with growth rate is significantly correlated (r=0.651,P<0.01);significantly correlated with cutting height (r=0.675, P<0.01);significantly correlated with number of branches (r0.129, P<0.05); no correlation with fresh-dry ratio (r=0.055,P>0.05); The sequence of correlation coefficients of four yield traits to grass yield was cutting height>growth rate> fresh-dry ratio> number of branches> fresh-dry ratio.3. The genetic diversity of77alfalfa materials were analyzed by10screened SSR primers,77alleles were identified and the average number of alleles per pair primers (N4) was7.7; the average number of effective alleles (NE) was3.5738; the average diversity index (I) was1.4526; the average expected heterozygosity (HE) was0.6778. The UPGMA analysis of Nei’s genetic distance clustered77alfalfa entries to8sub-groups derive from4groups. The SSR marker indicated wide gaps of genetic distance among the77alfalfa materials, which reflected the heterogeneity of alfalfa germplasm.4. Based on58obtained polymorphic loci, we analyzed the population structure of the77alfalfa materials, the results demonstrated that:When K(Group number)=4, the likelihood value is the largest, the tested materials can be classified into four groups. Analysis of the Q value of the alfalfa material in different groups, found that the Q value of77.92%of the material in the77alfalfa materials is greater than or equal to0.6, the genetic basis is unitary, while the Q value of other17alfalfa materials in each group is less than0.6, with a complicated genetic background. However the50materials which were assigned to specific groups, the proportion of those groups were18.18%,14.29%,27.27%,18.18%. The genetic diversity of all types of group comparison results indicated that the genetic diversity level in groups Ⅱ is the highest, followed by groups III, groups I, and the genetic diversity of groups IV is relatively low.