| China is the hometown of soybean; there were abundant soybean germplasm resources. It would be valuable to evaluate the genetic diversity of these accessions, but until now there were no thorough and systematic work done on this subject.The objective of this study was to analyze the genetic diversity of Chinese soybean germplasms and definite the genetic relationship of them on DNA level by using SSR markers. Through these analyses, instructions could be provided for collecting, using the soybean germplasms, and broadening genetic base in soybean breeding. Important information could also be obtained about the revolutionary relationship between different ecotypes. A total of 405 accessions was selected from the preliminary core collection, which were divided into 5 different ecotypes: northeast spring sowing soybean, Huanghuai summer sowing soybean, southern spring sowing soybean, southern summer and autumn sowing soybeans. A set of 67 SSR primers were used to analyze 405 accessions, and detected 502 alleles with averaged 7.49 alleles per locus. Simpson diversity index varied from 0.501 to 0.898 with the mean value of 0.765, and Shannon-weaver index ranged 0.707-2.445 with the mean value of 1.645.The main results were summarized as the following:1. Core primers of SSR were established to analyze genetic diversity of Chinese soybean resources firstly. Among 80 autumn sowing soybeans, 711 different alleles were detected with 102 SSR primers. By using these data, similarity coefficient matrix (SM) and its phenotypic matrix (CM) were established as a representative matrix (RM). Incomplete matrix calculated with a series of randomly selected alleles and compared to RM, among them, both SM and CM of 325 alleles from 47 primers were significantly related with 0.094 of the standard error. When primers increased to 60 and 67, the standard error could decrease to 0.054 and 0.049. So 60 SSR primers could be the minimum number used in the study. 67 SSR primers were selected with less than 0.05 of standard error, 2-6 loci were distributed on each linkage group with 50cM averaged genetic distance between two loci. Defining core primers was conductive to analyze genetic diversity of soybean core collection.2. Genetic diversity distribution and characteristics of five ecotypes were clarified at molecular and phenotypic levels. 405 soybean accessions were amplified with 67 SSR primers, 432 alleles were detected in southern autumn sowing soybean, 423 in southern spring sowing soybean, 418 in southern summer sowing soybean, 414 in Huanghuai summer sowing and 335 hi northeast spring sowing soybean. According to the variation extent, the order from high to low is: southern autumn>southern spring>southern summer>Huanghuai summer>northeast spring. Huanghuai summer sowing soybean had the highest Simpson index and Shannon-weaver index, they were 0.708 and 1.470 respectively. The second was southern spring sowing soybean, Simpson index and Shannon-weaver index were 0.704 and 1.469 respectively. Northeast spring sowing soybean had lower Simpson index and Shannon-weaver index, they were 0.638 and 1.233 respectively. The genetic diversity of each ecotype showed Huanghuai summer> southern spring> southern summer> southern autumn> northeast spring. Also, Huanghuai summer sowing soybean had the highest Shannon-weaver index for phenotypic characters, whereas the ranking order was different from molecular marker of other ecotypes, which was northeast spring > southern summer > southern spring> southern autumn. The lowest average Jaccard genetic similarity coefficient of Huanghuai summer sowing soybean was 0.172, the second was 0.174 of southern spring, 0.186 of southern summer, 0.200 of southern autumn, and the last was 0.225 of northeast spring. However, the orders of Jaccard genetic similarity coefficient based on phenotypic characters showed: Huanghuai summer sowing soybean>northeast spring sowing soybean> southern summer sowing soybean> southern spring sowing soybean>southern autumn sowing soybean. Therefore, the...
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