Abstract:

【Objective】 The objective of the present study was to explore the differentiation of genetic structure of the general population of released soybean cultivars in China and the genetic diversity, genetic specificity and genetic relationship of the geo-ecological subpopulations and released period subpopulations for serving the genetic improvement of soybeans in China with relevant genetic background information in selecting key parental materials from the population. 【Method】 A total of 64 simple sequence repeat (SSR) markers scattered on the whole genome were used to analyze the differentiation of genetic structure of the population with a sample of 378 out of total 1 300 soybean cultivars released during 1923-2005 in China under the software Structure Version 2.2, to analyze the genetic differentiation of the population into geo-ecological subpopulations and released period subpopulations and to analyze the genetic diversity, specificity and relationship of the subpopulations. 【Result】 The Chinese soybean released cultivar population was composed of seven groups of germplasm and obviously differentiated into geo-ecological subpopulations and released period subpopulations with different composition of germplasm groups. Each geo-ecological subpopulation held its own specifically existent, deficient and complementary alleles, which reflected ecological specificity of its genetic source. Along with the advance of released period, new germplasm was introduced into the subpopulations, which made specifically existent, deficient and complementary alleles added to the subpopulations and, therefore, made the new subpopulations with their new specificity. In comparison with the Chinese wild soybean population and landrace population, the Chinese released cultivar population has relatively narrow genetic background due to the bottle-neck effect of a limited number of ancestors. Among the province subpopulations, the number of total alleles and that of complementary alleles in Heilongjiang and Jiangsu subpopulations were the first and second largest due to a relatively wide source of ancestors and broad genetic background. The number of total alleles in the 1923-1970 subpopulation was the least; it increased along with the advance of released period and that in the 2001-2004 subpopulation was the largest even only a short period involved, indicating its relatively high genetic diversity and broad genetic background. 【Conclusion】 The present results demonstrated that geo-ecological differentiation and released period differentiation existed in Chinese released soybean cultivar population, which caused the subpopulations having their own genetic specificities characterized by their germplasm composition and specifically existent, deficient and complementary alleles. All the subpopulation specificities have laid the genetic bases of germplasm or gene exchange among the subpopulations in future soybean breeding.

Key words: released soybean cultivar population, population differentiation, genetic structure, genetic diversity, genetic specificity