QTL Mapping Of Seed Traits In Introgression Lines Derived From An Interspecific Cross Between Cultivated And Wild Soybean From South China

Soybean is an important oil crop in the world,which can provide plant protein,oil and healthy and others beneficial components for human beings.Annual wild soybean(Glycine soja Sieb.et Zucc.),which possesses many elite traits,such as small seed shape,more pods and grains,and excellent resistance to various environmental factors,is progenitor of cultivated soybean(Glycine max(L.)Merr.).It is an important research field for soybean genetics and breeding to utilize the wild soybean genetic resources to improve the cultivated soybean varieties.The wild soybean in South China is closest to the equator in the world,which must accumulate favorable genes in this specific environment.Soybean seed appearance traits,such as size-shape,seed coat color,are closely related to its commercial value.So many breederes continu to paying attention to seed appearance traits.Two introgression populations(including 173 BC1 and 75 BC2)were used in this study,which derived from the initial crosses which untilized a wild soybean accession Z4 from Guangdong Ruyuan as the donor parent and cultivated soybean varity Guixiadou 2(GXD2)as the recipient parent.The character data,including seed length,seed width,seed thickness,seed length-width ratio and so on,were obtained by Image analysis software.On the basis of past research,one hundred and sixty-nine pairs of SSR markers were used to detect the genotypes of the introgression lines.108 quantitative trait loci(QTLs)related to seed trait were identified based on combination genotype dates with the phenotype dates.These results can help discovering new genes from wild soybeans,and provide breeding materials for molecular design breeding of special soybean.The main results are as follows:(1)Seven different soybean seed traits,seed length(SL),seed width(SW),seed thickness(ST),seed length-width ratio(SLSW),seed length-thickness ratio(SLST),seed width-thickness ratio(SWST)and circularity(CS),were investaged.The average value of traits in the BC1 introgression lines were such as: seed length 6.17 mm,seed width 4.90 mm,seed thickness 4.27 mm,seed length-width ratio 1.27,seed length-thickness ratio 1.44,seed width-thickness ratio 1.15,and circularity 0.82.The average value of traits in the BC2 introgression line were such as: seed length 6.30 mm,seed width 4.99 mm,seed thickness4.76 mm,seed length-width ratio 1.27,seed length-thickness ratio 1.33,seed width-thickness ratio 1.05,and circularity 0.82.The results show that all traits were clearly separated.The value of seed length,seed width,seed thickness,seed length-width ratio,seed length-thickness ratio and circularity traits in BC1 population were between parents,while the width-to-thickness ratio showed transgressive inheritance.The value of seed length,seed width,seed thickness,seed length-to-width ratio and circularity traits in BC2 population were between parents,but lower than parents in seed length-to-thickness ratio and seed width-thickness ratio.The introgression of the wild gene significantly changed the seed traits of progenies,indicating that wild gene caused a wide variation in population.(2)The number of molecular markers was increased.Based on the existing research in our laboratory,the QTL of grain character was determined.In order to narrow the QTLs interval.SSR primers were further searched to narrow down the range of markers at both ends of the QTL loci..There were 111 SSR markers uniformly distributed on 11 chromosomes of soybean selected for polymorphism detection between two parents.Among them,39 pairs of SSR markers showed good polymorphism,and the polymorphism marker accounted for 35.1% of the total markers.These 169 pairs of SSR markers cover the length of the soybean genome of 2465.43 c M.Molecular markers were relatively evenly distributed on each linkage group,with the largest number of markers on chromosome 1(15 markers),and the smallest number on chromosome 10,14,15 and 16(5markers).The longest linkage group was chromosome 2 linkage group(286.26 c M),and the shortest genetic distance was chromosome 14 linkage group(15.67 c M).(3)The QTL of seed traits was mapping.Combining the phenotypes dates and genotypes dates of the introgression lines,108 QTLs for the main seed traits were initially mapped.There were 38 QTLS for seed length,which 4 were confirmed by previous studies.There were 5 QTLS for seed width,which 1 were confirmed by previous studies.There were 6 QTLS for seed thickness,which 1 were confirmed by previous studies.There were 10 QTLS for seed length-width ratio,which 2 were confirmed by previous studies.There were 11 QTLS for seed length-thickness ratio,which 1 were confirmed by previous studies.There were 21 QTLS for seed width-thickness ratio,which 2were confirmed by previous studies.There were 38 QTLS of circularity.