Genetic Diversity Research Of Germplasm Resources In Medicago Ruthenica

Medicago ruthenica is a forage with well palatable, belongs to Medicago L., Leguminosae. It is widespread in the North of China, and has good winter hardiness and drought resistance, therefore it is used generally to establish the artificial grassland, to prevent the soil erosion and to improve the degenerated grassland, etc. The genetic diversity about 50 accessions of this material collected from Inner Mongolia was analysed at three levels of the phenotypical, cytological and DNA in this study. Main results were obstained as follows:Phenotypic diversity was obtained by analyzing 13 morphological and 8 agronomic traits. It existed the significant variance and extremely significant difference among the accession studied, which the coefficients of variation distributed from 4.90%～90.96%, genetic diversity index was different between 0.62 and 2.07 for all 21 phenotypic characters, while the morphological traits were variant than agronomic traits. The results of correlation analysis indicated that it existed also the correlation each other among the traits studied, even through the significant correlation or extremely significant correlation existed between some traits. The results of principal component analysis revealed that some traits, such as width and areas of mid-leaflet, pod shape, 1000-seed weight, number of racemes/ twig, number of flowers/ pod, growth rate, and dry matter yield, etc. were the main factors for phenotypic diversity. The accession collected from the homoclime or homoplastic regions could be clustered in the same groups by cluster analysis.The genetic diversity of cytological characters was analysed on 4 representative accession of the materials. The result showed that, they are diploid with the constant chromosomes numbers and the number of chromosomes is 2n=16. The length of chromosomes was 1～4μm what belong to small chromosomes. The karyotypes was 1B for two accession, which is very symmetrical and original, it was 1A for other two accession, which is more evoluant than 1B.Genetic diversity on molecular levels was tested by SSR markers. The results showed that 18 primers could produce clear and polymorphic bands. A total of 136 fragments were amplified from 18 primers, of which 109 bands (80.09%) were polymorphic. Effective alleles were 1.5006 and DNA diversity index were 0.2223 on average. Polymorphic information content (PIC) was 0.3236 on average, and gene differentiation coefficient was 035264. All 50 accession could be clustered mainly 8 groups by cluster analysis, as the same results of phenotypic diversity study, the accession collected from the same or similar regions could be clustered in the same groups.The variation was detected by phenotypic techniques was significantly higher than that was detected by molecular variation...