A Study Of Genetic Diversity Of Wild Soybean In Chongqing And Three Gorges Surrounding Areas

Subgenus soja, a most important one in Glycine Willd., contains cultivated soybean (Glycine max (L.) Merr.) and annual wild soybean (Glycine soja Sieb. & Zucc.). There is an easier hybridization between them and a good fecundity in their filial generations. In light of this, wild soybean with a high genetic diversity can be used to broaden the genetic base of cultivated soybean.Located in the upper reaches of Yangtze River in the east of Southwest China, Chongqing and the Three Gorges'surrounding areas have a unique environment for the growth of wild soybean. According to Vavilov's theory of eight crop origin centers, soybean originates from mountainous regions and the adjacent areas in the central and western part of China, i.e. Hunan, Shanxi, Hubei, Sichuan and Chongqing. To date, few reports have been made upon the researches of soybean in Chongqing and the Three Gorges'surrounding areas. A comprehensive analysis of wild soybean's genetic diversity in these areas can provide some basic information for the germplasm conservation and molecular breeding in the future.This study choosed 20 primers to evaluate genetic diversity of Chongqing's subgenus Soja and surrounding areas'wild soybean accessions. We also investigated isoflavone, protein and fat contents of subgenus Soja in Chongqing. Linkage disequilibrium analysis was firstly conducted, using 3 SSR marker loci in each linkage group. Then we conduct the association analysis between 124 SSR loci and quality traits such as isoflavone, fat and protein. Several conclusions would be drawn from this research as follows:1. The wild soybean accessions in Chongqing and the Three Gorges'surrounding areas had abundant allele variations, and the genetic diversity in this region was at a high level. In view of the genetic diversity of wild soybean accessions, western Hubei and southern Shaanxi owned most abundant wild soybean accessions, and Chongqing ranked the second, and the lowest regions were eastern Sichuan and northern Guizhou. In view of the special allele variations, western Hubei owned the most abundant. The research also found that the genetic background and population structure of wild soybean accessions were strongly affected by geographical orgin. Introgression took place in different populations.2. Subgenus Soja in Chongqing revealed rich allele variations. Besides the allele variations and special allele variations of wild soybean accessions was large in quantity, and the variations were abundant, and the genetic diversity indexe higher, so that the genetic diversity of wild soybean was higher than that of its cultivated landrace. As the genetic diversity of wild soybean accessions in the County Liangping, Yunyang and Dianjiang, which located in junction area of northeast and central Chonqing, was at a high level, these three regions should be key regions for conservation and research of wild soybean. As to landrace, the southeastern Chongqing showed the highest level of genetic diversity, and the western Chongqing presented the richest genetic variation, wherefore these two regions deserved its due attention in the research of cultivated soybean. In the cluster analyses and population structure, accessions from a same region could gather easily, but the groups divided by these analyses showed an insignificant relation with the geographical origin.3. The mean contents of protein and fat in Chongqing wild soybean accessions was in a lower level than those of its cultivated soybean landraces, but it was an opposite case with the isoflavone content. The isoflavone content varied evidently in different types of subgenus Soja and genetic resources with a high isoflavone exist in landrace cultivated soybean accessions, of which, five quality high-isoflavone soybean genotypes had been discovered. The contents of protein, fat and isoflvone were various among different ecological zones of Chongqing, and there were advantageous areas for specific quality traits. The content of isoflavone had a significantly negative correlation with that of the protein, also a positive correlation with that of fat, but the correlation was insignificantly positive in the cultivated landraces.4. The linkage disequilibrium of wild soybean accessions in Chongqing was higher than that of the cultivated landraces. In wild soybean accessions, most linkage disequilibrium of pairwise loci concentrated on A1 and D1a linkage groups. As to landrace, most were distributed in C1, G and D1b linkage groups. Both populations of wild and cultivated landraces in Chongqing were composed of two subpopulations. As per the association analysis, 58 SSR loci in total associated with the protein, fat and isoflavone content, among which 49 belonged to wild soybean and other 13 belonged to landrace.