Genetic Diversity And Association Analysis Of Agronomic And Quality Traits Of Soybean Cultivar Released Based On SSR Marker In Northeast China

Soybean is the major food and cash crop in China, and is an important source of fat, protein and health-care active substance. Northeast China is the main soybean producing area. A total of 1300 soybean cultivars had been released in China from 1923 to 2005, including 682 from northeast China. Based on the previous research, 140 northeast soybean cultivars were conducted in the following research by 157 SSR markers and 29 EST-SSR markers uniformly distributed in the nuclear genome of 20 LGs. (1) Analysis of the genetic diversity of soybean cultivars in northeast China and exploration of the genetic specificity and complementary in different location and at various periods. (2) Analysis of population genetic structure of northeast soybean cultivars. (3) Analysis of LD and attenuation of northeast soybean cultivars. Then breeding traits QTL are located. The results are as follows:1. There were 878 alleles of genetic richness,4.72 alleles per locus,0.482 of average PIC inside of the released cultivar population detected by 186 SSR markers. According to the Neighbor-Join clustering method, northeast soybean cultivars were divided into three subgroups composed of Heilongjiang, Jilin and Liaoning soybean cultivar. Besides, Heilongjiang subsets can be divided into 3 small subgroups. According to provincial cluster analysis, Heilongjiang Is closed to Jilin and far from Liaoning. According to period cluster analysis, Ancestor is closely related to the 1971-1990 sub-groups and distinctly related to 2001-2005 sub-groups.2. Analysis of specificity and deficiency of northeast soybean cultivars between different provincial and periodic subpopulations shows, (1) There are 97,22 and 27 special alleles in Heilongjiang, Jilin and Liaoning respectively. There are 30,65 and 75 deficient alleles in Heilongjiang, Jilin and Liaoning respectively. (2) Deficient alleles in provincial subpopulations and period subpopulations are 30,65,75 and 73, 25,20,4,1, respectively. According to these results, Heilongjiang soybean cultivars, on both supplementary allelic variation and specific allelic variation, have the potential application value to expand genetic diversity of Jilin and Liaoning's soybean cultivars, which benefits from vast territory, rich genetic and parents wide variety of sources.new genetic diversity of Released cultivar increased compared with old ones. But, recently, the genetic basis of northeast soybean cultivars became increasingly narrow, leading to the unity of the genetic basis of population.3. Total 140 northeast soybean cultivars can be clusted into five subpopulation based on the Hardy-Weinberg model detected by STRUCTURE software, the rectificatory population structure as the co-variable for association mapping. Under the significant level of p<0.005, association mapping results showed that,38 SSR and EST-SSR markers associated with seven breeding target traits (days to flowering, plant height,100-seed weight, content of moisture, content of total protein, content of fat, mix of protein and fat). There were a few locus associated with two or more traits simultaneously, which might be the genetic reason of correlation among traits or pleiotropic phenomena. In addition,11 associated markers were in agreement with mapped QTLs from FBL mapping procedure. Satt134 associated with plant height was the highest explained trait (0.26, p<0.000001) in this study.4. LD analysis of total 140 northeast soybean cultivars by TASSEL software shows that among 17205 locus pairs from 186 SSR locus of 20 LGs, the different degrees of LD were detected not only among syntenic markers but also among nonsyntenic ones. With statistical probability's support, there are 1245 coupled locus which accounts for 7.24% of gross amount of locus pairs, the number of syntenic LD locus is 139, accounting for 11.17% of LD pairs. D'average value among 1245 LD pairs is 0.38, the part of greater than 0.5 accounting for 9.48% of total LD pairs. D' average value among syntenic and nonsyntenic pairs is 0.44 and 0.37, the part of greater than 0.5 accounting for 24.46% and 7.69%. Synteny pairs of SSR and decay scatter chart of genetic distance by SPSS software shows that LD of northeast soybean cultivars decayed fast because of the minimum distance extended by LD decay was very small.As the genetic distance between locus increases, the strength of LD between locus showed decreasing trend.