| Our country has an abundance of resources of cultivated soybean, Glycine max (L.) Merr, including a large number of local variety and released variety. It is an important way for vegetable soybean breeding to analyze the genetic variation of cultivated soybean germplasm in China and select elite germplasms; Researching the features of genetic variation of fresh soybean seed traits and mapping the marker loci associated QTL of fresh soybean seed traits, are useful for molecular marker assisted selection of vegetable soybean, we analyzed a representative sample with 212 released varieties and 202 local variety soybean accessions with 102 simple-sequence repeat(SSR)markers, the purpose is to reveal the genetic diversity of cultivated soybean in China, the features of genetic variance of fresh seed traits, and locate QTL loci of vegetable soybean fresh seed traits using association analysis method. The main results are as follows:(1) There were 474 alleles detected in 404 cultivated soybean from the Chinese countrywide area, the average allele number (A) per locus was 4.68, the average polymorphism information content (PIC) was 0.462. The locus with max A value was Satt185,which was on linkage group E(A value was 16, PIC value was 0.895). The genetic diversity of overall population was not high. The detected alleles number in the 185 local soybean varieties in Southern China was 458. the average A value per locus was 4.49, the average PIC value was 0.431.(2) By comparing the genetic diversity of the six ecological zones, we found the PIC value of released varieties was little higher than local varieties'in ecological zonesⅠandⅡ, the PIC value of local varieties was higher than released varieties in ecological zonesⅢ,Ⅳ,ⅤandⅥ, the difference had gradually increased. According to Nei-1983 distance, the soybean cultivars in China are divided into nine sub-groups with the "Neighbor-Joining tree" method for An unrooted neighbor-joining tree. From the result, we found the materials from the same ecological regions had gathered together, indicating that soybean cultivars of various geographic populations are genetically quite different.(3) The amplitude of sucrose content of fresh seed in all materials in China was large, which contained foreign materials', the average value of two years of sucrose content materials were separately 67.23mg/g and 65.51mg/g. The variance of sucrose content of two years in six ecological zones were smaller, the same to the result between local variety and released variety. The amplitude of 100-pods fresh weight and 100-seeds fresh weigh in all materials in China was also large, their average was separately 191.09g and 44.25g. The variance of both traits were all large among ecological zones, the max and min zone of 100-pods fresh weight was separately ecological zoneⅢandⅤ, the difference of averages was 73.02g. the max and min zone of 100-seeds fresh weight was separately ecological zoneⅢandⅠ, the difference of averages was 21.28g.(4) The correlation between sucrose content and 100-pods fresh weight and 100-seeds fresh weight was all not significant, correlation coefficients were 0.049 and 0.056, while the correlation between 100-pods fresh weight and 100-seeds fresh weight was highly significant, the correlation coefficient was 0.622, we screen 40 elite germplasm according to 5% of total resources to the highest and lowest sucrose content of fresh seeds, most of them were from the ecological zonesⅠ,ⅡandⅢ. Screening results show that every ecological zones had a number of excellent resources, these recources can be improved directly, or be used as breeding improved intermediate material.(5) Through the analysis of LD on 20 linkage groups for all materials in China, we found that regardless of linear combination, or non-linear combination, they both had a certain degree LD, but the combination number of D'>0.5 was very small, which was only 2.13% of total. There had a wide range LD structure on 20 linkage groups in the 158 materials in Southern China, but the combination number of D'>0.5 was only 5.67% of total. Based on the results, we found D'of Cultivated soybean in China was rapid decay with genetic distance.(6) Through association analysis,41 marker loci were detected in cultivated soybean in China, which were related to sugar content,100-pods fresh weight and 100-seeds fresh weight. There were 11 marker loci Associated with the sucrose content, the satt313, was also detected by Kim et al (2005), the loci of max explained portion of phenotypic variation was satt141 (explained portion was 0.07); the marker loci associated with 100-pods fresh weight and 100-seeds fresh weight were separately 23 and 14, their max explained portion of phenotypic variation loci were separately satt588 (explained portion was 0.301) and satt095 (explained portion was 0.355).22 marker loci were detected in local soybean in Southern China, which were related protein content, fat content, starch and soluble sugar content. The marker loci number associated with 4 traits are 3,13,3 and 9. The loci of max explained portion of phenotypic variation of 4 traits were separately satt590 (0.111), satt488 (0.237), satt185 (0.24) and satt373 (0.167). |
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