| Alfalfa(Medicago sativa L.)is an important perennial,cross-pollination,tetraploid leguminous forage that is known as the “king of forage” and “forage queen”and widely planted in the worldwide.Genetic diversity of germplasm is originated from long-term evolution,and plays a key role for its survival and regeneration.Studying genetic germplasm diversity is of great significance for rational use and protection of germplasm resources.Seed functional traits are an important part of biodiversity,which have rarely been studied in previous research.The paper studied the genetic diversity of seed functional traits including seed size,seed dormancy,seed fluorescence and so on,in 46 alfalfa germplasms from seven countries.In addition,10 germplasms was used to analyze the genetic diversity by SSR markers.The aim is to lay the foundation for extensive and in-depth understanding genetic diversity of alfalfa germplasm and provide the basis for new varieties breeding.The main results are as follows.1.The results on genetic diversity of 46 alfalfa germplasm in seeds size and morphology showed that there was a significant difference in variation among and within traits(P < 0.05),and variation among germplasms was greater than that within species.Seed size is positively correlated with length,width,circle length,circle width,perimeter,however,a negative relation between seed size and width-length ratio was observed.Seed size can be divided into 5 levels according to UPOV TGP/7.2.The results on genetic diversity analysis of seed dormancy characteristics of46 alfalfa germplasm sources showed that the mean hard-seed range was38.7 %-0.7 %,and the coefficient of variation ranged from 0.0 % to 173.2 %.There was a significant difference in variation among and within germplasm,and variation among germplasm(111.0 %)was greater than that within germplasm(0.4 %),indicating that alfalfa germplasm was rich in genetic diversity.According to seed hard rate,46 alfalfa germplasms can be divided into 4 categories by cluster analysis.3.The results on genetic diversity of seed fluorescence characteristics of 46 alfalfa germplasms showed that the average fluorescence rate after 24 h water absorption was 58.6 %,ranging from 29.2 % to 88.0 %.Variations among and within germplasm differed significantly,and variation among germplasm(35.0 %)was greater than that within germplasm(0.2 %).According to fluorescence rate,46 alfalfa germplasms can be divided into three categories by HemI software.The fluorescence rates of Saranac AR,Xinjiang Daye,and Grassland No.2 with 24 h water absorption were all over 80.0 %,indicating a contribution to time and labor saving in the authenticity identification of seeds.4.Population structure and genetic diversity of 10 alfalfa germplasms(400genotypes)by SSR analysis showed that a total of 337 alleles were amplified,and the average heterozygosity and polymorphism information content was 0.934 and 0.932,with the Shannon's index was 0.130.Four hundred alfalfa genotypes in this study were divided into four categories by STRUCTURE software,and this result was consistent with that form Neighbor-joining clustering and principal component analysis.The AMOVA analysis results showed that intra-variety variation(95 %)was greater than inter-variety variation(5 %),which was different with the above mentioned genetic diversity of seed functional traits.The results showed that 400 alfalfa genotypes have high genetic diversity. |
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