| Drought is an abiotic stress that seriously affects crop growth and development and leads to reduced yield.Soybean [Glycin Max(L.)Merr.] is an important oil crop and is a drought-sensitive crop.Soybean seedlings are very sensitive to drought stress,in which the roots are the first to feel the change of soil moisture,and can quickly change the physiological and biochemical changes.The drought tolerance of soybean roots is a quantitative trait,which is affected by many factors of heredity and non heredity.Exploring the genetic characteristics of soybean root drought tolerance at seedling stage can provide theoretical support for molecular marker-assisted breeding,and thus improving soybean yield plays an important role in ensuring food safety in China.In this study,152 and 326 northern spring soybean germplasms were used to control water content by weighing method at seedling stage,and multiple drought and rewatering were used to simulate drought environment to identify root drought tolerance of the two groups.The genomes of 152 soybean populations and 326 soybean populations were scanned using 30519 SNP markers,and the genomes of 152 soybean populations were scanned using 210 pairs of SSR markers to analyze genetic diversity,population structure and linkage disequilibrium.The genetic maps of soybean root traits under drought from different sources in the past 15 years were collected.Based on 83 QTLs for root drought tolerance traits,a consensus map was mapped on the Soybase 2map using Biomercator 4.2 software,and meta-analysis was performed.The SNP loci,SSR loci and meta-analysis general QTL intervals obtained by association analysis were compared to obtain similar intervals,and the similar intervals were annotated.The results are as follows :The descriptive statistics of root drought tolerance traits of 152 and 326 northern spring soybean seedlings were carried out.The coefficient of variation of 152 soybean germplasm was between 10.79 % and 39.92 %,and the coefficient of variation of relative drought-tolerant root tip number was the largest,which was 39.92 %.The coefficient of variation of 326 soybean germplasm was between 5.77 % and 15.21 %,and the coefficient of variation of relative drought-tolerant main root length was the largest,which was 15.21 %.It shows that there are extensive genetic variations in all traits.Using principal component analysis and membership function method,152 soybean populations were screened for the extremely drought-tolerant variety Fengshou7,and 326 soybean populations were screened for the extremely drought-tolerant varieties Yongfengdou,Tiejiaqing,Tongnong 5,39238 and Lvzhadou.The D value of Fengshou 7 was the highest,which was 0.95.The association analysis of the two populations was carried out by using SNP and SSR,and the mixed linear model(MLM)was used.At the same time,the genetic relationship matrix and the population structure result Q matrix were used as the covariate correction model.At the significant level of-Log10(P)≥ 3.5 or-Log10(P)≥ 4,a total of 157 SNP loci associated with drought tolerance of soybean roots at seedling stage were associated.Among them,152 soybean populations were associated with 76 SNP markers,distributed on 17 chromosomes of soybean,and the most SNP markers were on chromosomes 5 and 16,with 20 SNP markers each.A total of 51 pairs of SSR markers were associated with 152 soybean populations,which were distributed on 19 chromosomes of soybean.Among them,chromosome 13 had the most SSR markers,with 7 pairs.A total of 81 SNP markers were associated with 326 soybean populations,distributed on 18 chromosomes of soybean,of which 12 SNP markers were associated on chromosome 8.Based on 83 published soybean root drought tolerance QTLs,12 common QTLs were obtained by meta-analysis.By aligning the loci associated with the two populations with the physical location of the common QTL interval,157 SNP significant loci were optimized to 21,of which the ss715630660 marker and ss715632811 marker on chromosome 18 were simultaneously detected in multiple analysis methods.The soybean genes in the 50 kb region around the location of 20 sites were searched,and the functions of their Arabidopsis homologous genes were analyzed.Finally,57 soybean genes were obtained,and there were 8 published genes around them.The presence of MYB88 and b ZIP111 in the published genes was closely related to the drought tolerance of soybean,which proved that the combined analysis method could provide a novel site verification mode.The function of soybean gene was predicted by searching the homologous gene function of soybean gene in Arabidopsis thaliana.Four genes,Glyma.03g250600,Glyma.05g157000,Glyma.05g157400 and Glyma.06g177000,which may be closely related to drought tolerance of soybean seedling roots were obtained. |
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