Effect Of Domestration And Inbreeding On Genetic Diversity In Soybean Using SSR Marker

Genetic diversity of 40 wild accessions,40 landraces and 40 improved cultivars of soybean were analyzed with 56 pairs of SSR primers to evaluate the influences of domestication and breeding on soybean genetic patterns and hereditary constitution, which would provide a theoretical basis for the broadening of the breeding hereditary basis and a feasible experimental system for the investigation molecular mechanisms of breeding and identification of new functional genes.The main results are as follows:1)Based on the integrated analysis of all the 120 accessions on numbers of alleles with 56 pairs of SSR primers,we got 530 alleles in all.Thereinto,there were 481,287 and 262 alleles in wild soybean,landraces and improved cultivars,respectively. 49.9%of alleles were lost during domestication,while only 26.5%during breeding, showing a more severe lost of gene in the domestication process.The PIC,the gene diversity(He)and Shannon Index(I)shown in wild soybean and landraces are 0.710 (PIC),0.758(He),1.696(I)and 0.536(PIC),0.599(He),1.158(I)respectively,while those of improved cultivars are 0.498(PIC),0.557(He)and 1.053(I),which indicated a decrease in the trend of the genetic diversity during the domestication and breeding process of soybean from wild accessions,landraces to improved cultivars.And 24.5%(PIC),21.0%(He),31.7%(I)of diversity were lost during domestication,While only 7.0%(PIC),7.0%(He),9.1%(I)during breeding.Analysis of the gene frequency distribution indicated a lost of genes especially the low frequency ones was detected, the number of low frequency alleles were depressed,while the number of high frequency ones enhanced.2)Based on the structure fig and the UPGMA tree,3 groups including wild group,landrace group and inbred group were shown in which the improved cultivar group was independent of the other two groups.The genetic distance between the wild and inbred group is farthest(0.180)and that between the wild and landraces group is farside(0.141),compared with that between the landraces and inbred group (0.113).It indicated a closer relationship between cultivars and landraces.The the genetic differentiation coefficient(Fst),obtained from the analysis of molecular variance(AMOVA),between improved cultivars and landraces(0.13)is smaller than that of the wild and landraces(0.15),which of the wild and improved cultivars(0.19) is the tiptop.This teindicated the soybean structure was changed during domentication and inbreeding process and the wild,landraces and improved cultivars were divided into 3 independent groups.In addition,there were some outliers locis(AY885233,Satt227,Satt373 and Satt184)according to the Ewens-Watterson Test,which correlated or linked with the agriculture character or adapt function and showed the obvious selected evidence. Therefor,this research provided a feasible experimental system to dig out abundance of functional genes.