Association Analysis Of Root Traits In Soybean Seedling Stage Under Drought Stress

Soybean is a major crop for both food and oil and feed in China,and is an important source of vegetable protein,which is in greater demand in agricultural production and life.Many regions in China are affected by drought stress,and soybean seedlings are sensitive to moisture changes,and the root system is the first part to feel the changes in soil moisture content,and root development is affected by drought stress,which in turn will reduce yield.In this study,we analyzed seven drought tolerance indicators related to seedling root phenotypes of 300 soybean germplasm resources under drought conditions,and identified drought-tolerant germplasm by screening for drought tolerance using the affiliation function method.linkage disequilibrium analysis,and phenotypic data and SSR molecular data using TASSEL V3.0 software was used to correlate the phenotypic data with the SSR molecular data,and to discover excellent allelic variants associated with drought tolerance in soybean seedling root traits and typical vector materials carrying excellent allelic variants.The main findings were as follows.Drought-stressed soybean varieties were water controlled using the weighing method with a sand-to-water volume ratio of 8:1 for control and 4:1 for drought-stressed sand-to-water.results indicated that there was extensive genetic variation in the drought tolerance of population varieties under drought stress.The coefficients of variation for relative drought tolerance root traits under drought stress ranged from 15.83% ?162.97%,with the largest coefficient of variation for relative lateral root number,which had a value of 162.97%;based on the drought tolerance performance of different soybean varieties,the 300 soybeans tested were classified into five categories using the intergroup linkage method in systematic clustering,with category V being the drought-tolerant variety;correlation analysis showed that seven The results of the correlation analysis showed that seven root-related indexes were highly significant and positively correlated;the 300 soybean varieties were classified into three classes according to the affiliation function method: three extremely drought-tolerant varieties,accounting for 0.01% of the total number of varieties,namely,Harvest 7,Suinong 04 and Heihe 26;68 moderately drought-tolerant varieties,accounting for 22.67% of the total number of varieties;and 229 drought-sensitive varieties,accounting for 76.34% of the total number of varieties.The results of population genetic diversity showed that a total of 1505 allelic variants were amplified by 210 pairs of SSR markers,and the variation of allelic variants carried by each marker ranged from 2 to 22.The population structure analysis of 300 soybean varieties showed that the natural population was divided into five subgroups,and linkage disequilibrium was distributed on all 20 chromosomes in the soybean genome,with varying degrees of linkage disequilibrium in both co-linear and non-co-linear SSR markers.210 pairs of marker loci were detected with 17,637 combinations,of which co-linear combinations accounted for 826 groups,accounting for 4.68% of the total,and the co-linear linkage imbalance was mainly distributed on chromosome 2(13),chromosome 3(11),and chromosome 6(10).The number of pairs of linkage disequilibrium supported by P<0.01 at paired co-linear combination loci was 364,accounting for 44.06% of the total pairs,and the mean value of D' was 0.338.The GLM and MLM models were used to correlate the drought tolerance indices of the seven root traits with the molecular data of the test materials.38 loci(83 times)were detected by the GLM model and 62 loci(111 times)by the MLM model.Among the 15 monozygous loci associated with multiple traits,four loci were associated with six root-related traits of drought tolerance index;one locus was associated with five root-related traits of drought tolerance index;five loci were associated with three root-related traits of drought tolerance index;and five loci were associated with three root-related traits of drought tolerance index.5 loci were associated with 3 root drought-related traits;and 5 loci were associated with 2 root-related traits.The phenotypic effect values of the loci jointly detected by the two models were calculated,and a total of 127 superior allelic variants were found for the seven related root indexes,of which 28 were rare allelic variants(distribution frequency <1%).sat-395-279,satt659-230,and satt301-251 had the largest phenotypic effect values,and Heihe 26,Harvest 7,and Harvest 6 carried several The above varieties can provide parental materials for selecting and breeding drought-tolerant soybean varieties.