| As an excellent legume forge,Stylosanthes (Sw.) is distributed widely in tropical and subtropical regions. Since the beginning of 1980s, a large number of Stylosanthes germplasm were introduced into China.Stylosanthes germplasm have been used widely in soil improvement, soil and water conservation as well as inter-cultivation of forest and herbage.With the continuous introduction and improvement of Stylosanthes germplasm,Stylosanthes germplasm is becoming richerin China. Based on the phenotypic data and EST-SSR molecular markers, genetic diversity and genetic structureof 407 Stylosanthes germplasm were analyzed.The best strategy for constructing Stylosanthescore collection was selected based on the two types of data, and the continuous data and the discrete data were integrated according to different radio.Stylosanthes core collection was constructed to provide reference and basisforthe further researchandutilization ofStylosanthes germplasm.The main results are as follows:(1) The genetic diversity of Stylosanthes was analyzed based on the phenotypic data. The results showed that the mean of the diversity index among 22 quality traits is 0.797 with a range of 0.077～1.352. The diversity index of seed color is the highest (1.352),and that of the seed mottle is the lowest (0.077); the variations of 5 quantitative traits were greater than 15%. The variation of plant height is the largest (40.49%), with a range of 7.70cm～150.80cm.The variationof the bract length outside the flowersis the smallest(17.02%), with a range of 0.40mm～1.47mm.(2) The 91 pairs of primers were selectedby the amplification of38 Stylosanthes materials from 25 different species. A total of 44 pairs of primers were amplified in all the materials, and the bands of the 39 pairs of primers were clear and polymorphic. 30 pairs of primers are chosen to amplified 407 Stylosanthes. The genetic diversity and genetic structureof Stylosantheswas analyzed based onEST-SSR molecular markers,and the results showed that 30 pairs of primers detected 185 alleles intotal. The average observed number of alleles was 6.167.The average effective number of alleles was 2.054.The average of Shannon diversity index was 0.968. The average of observed heterozygosity was 0.146.The average of expected heterozygosity was 0.485.The average of Nei’s genetic diversity index was 0.485.The average of polymorphic information content was 0.445. The value of K for the analysis of genetic structure was determined in terms of variation of △K.When △K reached the maximum, K=7, so the 407 Stylosanthesaccessions were divided into 7 groups.(3) Stylosanthescore collection was constructed based on the phenotypic data and EST-SSR molecular markers.Based on the sampling ratio of 20%, the strategy ofconstructing Stylosanthes core collection was selected and evaluated by assessment of genetic diversity parameters. The results showed thatstepwise cluster preferred sampling is better than stepwise cluster variability sampling, and deviation square method is better than other clustering methods.Between different genetic distance of continuous data, Euclidean distance is slightly better than Mahalanobis distance; among discrete data genetic distance,Jaccard similarity coefficient outperforms other genetic distances.According to the best construction strategy for continuous data and discrete data integration in proportion,the best ratio is 0.1:0.9.Besides,20% was chosen as the sampling ratio, and supplemented with 7accessions with special value toconstruct core collection in Stylosanthes, which contains 88 accessions.(4) The representative of Stylosanthescore collection was verified: the core collection have similar genetic diversity of phenotypic traits with initial collection in Stylosanthes exceptseeds mottle (192.601%) andstipule texture (152.423%). Retention rate of the genetic diversity parameters between core collection and initial collection based on the molecular data was similar, maintained at a range of 98.378%-124.469%; principal component analysis based on phenotypic data and molecular markers showed that core collection in Stylosanthes have similar genetic structure with initial collectionin Stylosanthes; the correlation analysis of phenotypic traits confirmed that the core collection have the same traits correlation of 84.333% of the initial collection, which could represent the initial collection.In summary, the results showed that core collection in Stylosanthes can be a good representative of initial collectionby the analysis of the genetic diversity,genetic structure and traits correlation of the core collection, and compared with the initial collection. |
