QTL Mapping For Some Stem And Leaf Traits Of Wild Soybean And Candidate Gene Analyses Of A Vining Growth Habit QTL QVGH-G

Wild soybean(Glycine soja Sieb et Zucc)is an annual and vining plant of genus Glycine in subfamily Papiliomatae,family Leguminosae.It has abundant genetic variation,especially rich in elite gene resources with tolerance to abiotic stresses or high seed protein content for soybean breeding.In comparison with cultivated soybean,wild soybean performs different plant type with vining growth habit,small leaflet and short petiole,which are the adaptation results to environment conditions.It is of great significance to reveal the genetic mechanism of these domestication-related traits to understand the evolution trend of G.Soja and to give some useful guidance for soybean plant-type breeding.In the present study,two recombinant inbred line populations(NJRINP and NJRI4P)derived from the crosses between a wild soybean accession P1342618B as a common male parent and two cultivated soybean cultivars Nannong 86-4 and Nannong 493-1 were used to map QTL of vining growth habit,plant height,stem diameter,leaflet length,leaflet width,petiole length and flower time traits,and candidate gene analysis of a major QTL qVGH-G-2 for vining growth habit was also conducted.The main results were as follows:There were significant differences of six stem and leaf traits between the parents of NJRINP and NJRI4P populations.Significant differences of these traits among lines in each of the two populations were also observed.In NJRINP population,the heritability value of plant height was the highest 92.91%,and that for stem diameter was the lowest 61.68%.In NJRI4P population,the highest and lowest heritability values were 92.54%and 53.75%for flower time and stem diameter respectively.Vining degree increased during the plant growth period.There was significant positive correlation between vining growth habit and plant height,while a negative correlation occurred between vining growth habit and stem diameter.A total of 19 QTL for the six traits were detected in NJRINP and NJRI4P populations.Among them,six QTL could be detected simultaneously in the two populations.Among the four QTL controlling plant height,qPH-G and qPH-L-2 in G and L molecular linkage groups(MLG)could be detected in both populations.LOD value and phenotypic contribution rate of qPH-L-2 could reach to 24.49 and 28.65%in NJRINP population,followed by the QTL qPH-G.However,in NJRI4P population,LOD value and contribution rate of qPH-G was 7.19 and 14.91%,then followed by the QTL in MLG L.qPH-G and qPH-L-2 were major QTL controlling plant height in these populations.Among the four QTL controlling stem diameter,qSD-O in MGL O was detected in both two populations.In NJRI4P population,LOD value and contribution rate was the highest,and the additive effect came from Nannong 493-1.No common QTL among three loci for leaflet length and four for petiole length was detected in the two populations,however,two of four QTL controlling leaflet width,qLW-A2 and qLW-L-2 were found in both two populations,and qLW-L-2 with the highest LOD values was considered as a major QTL.Since qLL-L,qLW-L-2 and qPL-L located near the marker Gm19sv484 in NJRINP population,there might be an important QTL controlling the leaf traits in the region.Among the six QTL for flowering time,qFD-L could be detected in both populations.Vining growth habit was investigated at beginning flowering(R1)and full maturity stage(R8)in 2013 and 2014,respectively.In NJRINP population,total three and four QTL for vining growth habit at beginning flowering(R1)in 2013 and 2014 were detected respectively.qVGH-Dla、qVGH-G-1 and qVGH-G-2 in MLG Dla and G could be found in both years.Two QTL,qVGH-G-1 and qVGH-L,for vining growth habit at full maturity stage(R8)could also be detected simultaneously in both years,and the contribution of phenotypic variation of the major locus qVGH-L gradually increased,while that of qVGH-G-2 remaining stable during the plants growth period.The location of qVGH-L was overlapped with the physical position of determinate habit gene Dtl.There was an epistasis effect between qVGH-G-2 and qVGH-L for vining growth habit.In NJRI4P population,only qVGH-G-2 was detected both in Rl and R8 stage.The mapping interval of qVGH-G-2 covered 351.6 kb,and 19 predicted candidate genes were identified.Most of them belonged to special enzymes or protein families except Glyma18g06781,Glyma18g06830 and Glyma18g06910 whose functions remained unknown.The tissue expression analysis of the 19 genes found that the expression levels of Glyma18g06861 and Glyma18g06870 in stem and leaf tissues of wild soybean male parent significantly higher than those in female parent Nannong 86-4.Sequence polymorphic analyses of six candidate genes,Glyma18g06861,Glyma18g06870,Glyma18g06840,Glyma18g06850,Glyma18g06890 and Glyma18g06920,showed that there were 3,3 and 4 nucleotide differences in the sequences of Glyma18g06840,Glyma18g06870 and Glyma18g06920 among the parents,and 1,3 and 2 nucleotide differences could lead to amino acid changes,respectively.Glyma18g06870 had the most SNP variation(74)and a deletion of three nucleotides AC A which leaded to the missing of asparagine-methioninein.It speculates that Glyma18g06870 might be a candidate gene controlling vining growth habit.