| About a fifth of the world's arable land is affected by saline-alkali stress,which severely hinders the world's crop production.Reasonable selection of saline-alkali-tolerant varieties is the most effective and economical way to solve crop yield reduction under saline-alkali environments.However,in actual breeding work,there are few related researches on soybean alkali-tolerance,and most of them focus on a single salt stress.Less work has been done to excavate excellent allelic mutations in salt tolerance and alkali tolerance in the same experiment.Soybean sprout stage is the stage that is more sensitive to salt-alkali stress,and it is also the weakest period of salt-alkali resistance in growth cycle.In severe cases,the soybeans will die and cannot continue to grow.Therefore,identifying the salt-alkali-tolerant soybeans during the germination period and discovering the closely related markers as points provides a rich theoretical basis for screening salt-alkali-tolerant germplasm resources and has important guiding significance for the cultivation of carrier varieties.In this study,the phenotypic values of 9 traits at the bud stage of soybean under saline-alkali stress were used to calculate the corresponding relative salt-alkali tolerance coefficient,and the phenotypic variation,correlation and principal component analysis were performed to evaluate the salt-alkali tolerance of the varieties.The selected 210 pairs of SSR markers were used to scan the whole genome of a natural population composed of 318 soybean varieties.Analysis of its genetic diversity and linkage imbalance characteristics,and the trait-marker association analysis was carried out based on the relative salt-tolerant data of soybean,and the excellent allelic variation and related carrier materials were discovered.The results were as follows:There were extensive genetic variation in salt-tolerant basic traits of population varieties.The coefficient of variation under salt stress was 9.99%?86.23%,the maximum variation coefficient of germination rate was 86.23%,and the coefficient of variation under alkaline salt stress was 9.28%?66.19%,and the relative seedling height variation The maximum coefficient was 66.19%;the salt tolerance of 318 soybean resources was divided into 5 grades: 1 extremely salt-tolerant variety(Kenjian 43),accounting for 0.31% of the total variety material,35 salt-tolerant varieties,accounting for the total material 11.01%,195 medium salt-tolerant varieties accounted for the largest proportion,accounting for 61.32% of the total varieties of materials,80salt-sensitive varieties,accounting for 25.16% of the total varieties of materials,7extremely salt-sensitive varieties,accounting for 2.20% of the total materials;Alkaline is divided into 5 grades: 3 extreme alkali-resistant varieties(Kaiyu 3,Hefeng 48 and Hefeng 51),accounting for 0.94% of the total materials,53 alkali-resistant varieties,accounting for 16.67% of the total materials,medium-tolerant There were 161 alkali varieties,accounting for 50.63% of the total materials,84 sensitive alkali varieties,accounting for 26.41% of the total materials,and 17 extremely sensitive alkali varieties,accounting for 5.35% of the total materials.The genetic diversity of 318 soybean resources was analyzed.1 502 polymorphic alleles were detected with 210 pairs of SSR primers.For each pair primer,2 to 21 alleles were detected in all cultivars with an average of 7.15 alleles;the average PIC was 0.537,ranged from 0.006 to 0.908.Among them,the average PIC value of chromosome 17 was the highest(0.707),and the average PIC value of chromosome 15 was the lowest(0.362).As the number of allelic variations increases,the PIC value also increases,but it does not showed a linear relationship.The number of allelic variations on chromosome 2 has more but the PIC value was relatively low,and the number of allelic variations on chromosome 17 has less,but the PIC value relatively high.The allelic variation and PIC value of each marker were further analyzed,and a total of 16 severely segregated loci were found.The population structure analysis of the natural group composed of 318 soybean resources shows that the population was divided into 7 subgroups,and certain correlation between subgroups.The maximum genetic distance between the subgroups POP1 and POP7 was 0.2316,all POP1 were varieties of Heilongjiang,and all of POP7 are local varieties.The minimum genetic distance between POP5 and POP6 was 0.0335,and the materials in POP5 and POP6 were all Heilongjiang varieties.A total of 20 819 combinations were detected for 210 pairs of SSR primers,and the number of collinearity combinations was 993,accountied for 5.01% of the total number of combinations.According to the paired collinearity combination loci P<0.01,the number of linkage disequilibrium logs supported was 582,accounted for 58.61% of the total ones,and the average value of D' was 0.357.The higher levels of LD with D' >0.5 were mainly concentrated in chromosome 2,9,11,19 and 20.Regression analysis of LD and genetic distance between collinear loci was performed.From the attenuation diagram,it can be seen that as the genetic distance increases,the D' value between loci decays,and the extended minimum attenuation distance was 4.40 c M.The GLM and MLM models were used to perform association analysis on 318 soybean varieties.The GLM model detected a total of 98 loci associated with 9 salt tolerance traits,and the MLM model detected 27 loci associated with salt tolerance.There were 23 loci detected in the two models at the same time,and the contribution rate of phenotypic variation was 1.19% and 16.04%.Among them,there were 5 loci with a contribution rate greater than 10%: Satt239(14.19%,relative germination rate),Aw132402(15.63%,relative germination potential),Satt357(15.93%,relative seedling height),Sat?267(12.31%,relative axis Fresh weight)and Satt245(13.52%,relative leaf fresh weight).The GLM model detected a total of 119 loci associated with 9 alkali resistance traits,the MLM model detected 28 loci associated with alkali resistance,and 26 loci were detected in both models at the same time.The contribution rate of phenotypic variation was 2.23% ? 22.51%.Among them,there were 8 loci with a contribution rate of greater than 10%: Sat?304(11.75%,relative germination rate),Satt301(18.25%,relative germination potential),Satt357(22.51%,relative seedling height),Sat?355(10.83%,relative seedling High)Aw132402(14.09%,relative hypocotyl length),Satt094(16.37%,relative leaf fresh weight),Sat?256(14.68%,relative leaf fresh weight)and Satt245(13.17%,relative leaf fresh weight).The phenotypic effect value was calculated for the detected loci.A total of 85 positive alleles were detected for 9 salt tolerance-related traits,of which 17 were rare alleles(distribution Frequency <1%),there were 7 alleles had a positive phenotypic effect value greater than 20.Among them,5 alleles had a positive phenotypic effect value greater than 20 and were rare alleles: Satt357-133(23.63),Satt339-236(23.25),Satt422-280(38.05),Satt245-188(59.36)and Satt519-258(25.17).Among the 23 loci associated with salt tolerance traits detected in the two models,average positive allele effect of Sct?190 locus was the highest(28.46),and that of Satt239 locus was the lowest(0.36).A total of 76 positive alleles were detected for 9 alkali-tolerance-related traits,of which 14 were rare alleles.There were 20 alleles had a positive phenotypic effect value greater than 20.Among them,8 alleles had a positive phenotypic effect value greater than 20 and were rare alleles: Satt237-232(36.19),Satt094-138(37.24),Satt357-133(114.72),Satt239-207(27.09),Satt665-312(32.04),Satt094-138(23.66),Satt245-188(82.14)and Sat?256-335(34.49).Among the 26 loci associated with alkali tolerance traits detected in the two models,average positive allele effect of Satt245 locus was the highest(40.63),and that of Sat?304 locus was the lowest(1.71).The extreme salt-tolerant variety Kenjian 43,the extreme alkali-tolerant variety Kaiyu 3,Hefeng 48 and Hefeng 51 selected in this study were all typical carrier materials.These materials were used in bred varieties and landraces.All were distributed,and these typical carrier materials could be used as parent materials. |
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