| It is very important to define genetic diversity of abundant Chinese soybean accessions, which is necessary to reserve and utilize those resources. The traditional way was to analyze their relationships from agronomic traits, but those traits were affected by environmental and unnatural factors. Genetic diversity of soybean germplasm and resources should be further studied from the DNA level, for phenotype traits had not enough to expound their relationships with cultivars increased. A sample was obtained at random from primary core collection constructed by the soybean laboratory of the Institute of Crop Germplasm and Resources of CAAS. 18 traits were analyzed, in the premise of 100% coincidence of quality traits and no significance in quantity traits, and 190 Chinese soybean genotypes were finally determined as a standard sample. 606 alelles were found in 60 loci, with each locus having a mean of 10 alelles, and the mean of gene diversity scores was 0.83, with a range of 0.55-0.99. Standard error of similarity matrices was analyzed and the correlation among cophenetic matrices was examined using Mantel correlation test. Genetic diversity was estimated by SSR markers using cluster analysis and principle component analysis. The proportion and strategy of Construction of soybean core collection were also studied. The followings were the main results and conclusions of the study.1. It was first studied how genetic relationships of soybean cu\tivais(G.max) were affected by species and numbers of SSR loci. The same locus showed the different level of genetic diversity and alelles in different population. The truly genetic relationship could be obtained from enough alelles. The scope of genetic diversity was reduced to a relatively smaller level, and the number of alelles used to analyze relationships among acessions became correspondently fewer. The core SSR primers might be selected according to distribution of the SSR loci in the soybean genome and gene diversity scores. The objectively genetic relationships of Chinese soybean cultivars could be reflected using over 570 alelles.2. Genetic diversity based on SSR data was not consistent with that determined by agronomic traits, and more genetic information would be obtained from SSR data associated with agronomic traits.3. Genetic diversity of Chinese soybean cultivars had close relation to geographical regions, and soybean geographical differentiation was obvious. There was high genetic diversity in the same soybean planting region, which led to genetic diversity not congruent with its geographical origin. Chinese soybean cultivars had three population of high genetic diversity. The first consisted of North spring planting soybean, Northeast spring planting soybean and Huanghuai summer planting soybean. The second was the population of South spring planting soybean and South summer planting soybean, and South autumn planting soybean was another high population of genetic diversity. Soybean cultivars might be several original places.4. Alelles, Shannon and Weaver,s index and the level of genetic diversity obtained from the different proportion of 50%,40%,30%,20%,10% shared by total population were compared in the same sampling ways of variety classification-proportion, when the proportion of sample was reduced to 10%, coincidence of alelles was 72.16%. Those index originated from random sample, variety classification-proportion sample and cluster-proportion sample were also compared. Alelles and genetic diversity index of variety classification-proportion sample were higher than those of random sample, but close to cluster-proportion sample. Variety classification-proportion strategy was a better choice for constructing soybean core collection.
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