| Annual wild soybean(Glycine soja Sieb.et Zucc.),which possesses many elite traits,such as multi-flowering,high protein content,and excellent resistance to various environmental factors,is progenitor of cultivated soybean(Glycine max(L.)Merr.).Wild germplasm maintains high levels of genetic diversity that is the most important resource for the improvement of cultivated soybeans.South China is the distribution area of the wild soybean that is closest to the equator in the world.Wild soybeans in a specific environment must accumulate favorable genes.This study established a wild soybean introgression database in South China using wild soybean Z4 from Guangdong Ruyuan as the donor parent and Guixiadou 2(GXD2)as the recipient parent,including 177 BC1 and 74 BC2 lines derived from the initial cross.One hundred and thirty pairs of Simple Sequence Repeat(SSR)markers with good polymorphism between the two parents were used to detect the genotype of the introgression line,and combined with the phenotype to identify quantitative trait loci(QTLs)for interested trait.This study provides new tools for discovery and utilization of favorable exotics alleles from wild germplasm and prepares materials for molecular design breeding.The main results as follows:1)There were 346 SSR markers uniformly distributed on 20 chromosomes of soybean selected for polymorphism detection between two parents.Among them,130 pairs of SSR markers showed good polymorphism,and the polymorphism marker accounted for 37.6%of the total markers.These 130 pairs of SSR markers cover the length of the soybean genome of 1726.90 c M,accounting for 75.36% of the total soybean genome.The maximum genetic distance between the markers was 56.49 c M,and the minimum genetic distance was0.87 c M,the average distance was 13.38 c M.There were 13 fragments that flanked by two markers whose genetic distance more than 30 c M.2)The use of 130 pairs of SSR markers to detect introgression genotypes revealed that the coverage of Z4 genome in BC1 introgression population reached 98.46%,the wild gene introduction rate in 174 families was 1.54%-45.38%,with an average of 21.23%.The introgression rate of wild gene introduction was concentrated between 15% and 25%.The coverage of Z4 genome in BC2 introgression population was 92.31%.The wild gene introduction rate was 0%-45.38% in 74 families,the wild gene average import rate was10.29%,and the introgression wild gene introduction ratio was concentrated in 5%-15%.3)Statistical analysis of the introduction frequency of wild alleles revealed that in BC1 introgression population,the wild allele introduction rate ranged from 0% to 62.15%,and with an average of 21.18%.In the BC2 introgression population,the wild-type gene introduction rate was 0%-48.65%,and the wild-type gene average introduction rate was10.29%.It is difficult to find the same loci of high introduction rate for the wild type alleles at BC1 and BC2,but at the same time there were two low introduction rate regions at Satt407 on chromosome 1,at the position of 99.593 c M,and Satt578 on chromosome 4,at the genetic distance of 65.078 c M,where the wild allele introduction rate were 0%,and these two regions were predicted to be the cold spot region where wild alleles were unlikely introduced.4)In 2016 and 2017,we measured 15 important traits,including first flower time(FT),plant height(PH)and one hundred seeds weight(HSW)and so on.All traits were clearly separated.The introgression of the wild gene significantly changed the traits of progenies,indicating that wild gene caused a wide variation in population.5)Combining the phenotypes and genotypes of the introgression lines,191 QTLs were initially mapped for the main traits.One FT QTL,four NS QTLs,one SW QTL,two NIP QTLs and five N1 SP QTLs were detected both in BC1 and BC2.Eleven QTL were detected in two years in BC1 introgression population,while 3 QTL were detected in two years in BC2 introgression population. |
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