Drought Tolerance Identification And Gene Discovery In Soybean

Soybean [Glycine max?L.?Merri] is the main source of plant protein and edible oil in China,and plays an important role in agricultural production.Soybean is a drought sensitive crop,and soybean production is often affected by drought,so it is very important to screen elite soybean germplasm with drought tolerance and excavate drought tolerance genes.In this study,410 soybean accessions were evaluated for drought tolerance at the germination stage,and 247 accessions of them were evaluated for drought tolerance at the adult stage,and soybean accessions with drought tolerance were screened.Genome-wide association analysis were conducted by combining with SNP data,and 75 SNPs with significant signal were detected.The main findings are as follows:1.A total of 10 accessions with high drought tolerance at germination and adult stage were screened by phenotype identification.The drought tolerance of 410 soybean accessions at the germination stage were evaluated by using PEG6000.The results showed that the germination rate?GR?,germination energy?GE?,germination drought index?GDI?and germination index?GI?under drought stress condition were significantly lower than those of the control,and there were significant differences among the genotypes;Relative germination rate?RGR??relative germination energy?RGE??germination drought tolerant index?GDTI??germination stress index?GSI?and membership function value?MFV?were all significantly correlated.The MFV were used to comprehensively evaluate drought tolerance,as a result,410 soybean accessions could be divided into 6 grades.Three accessions with highest drought tolerance were in grade 1,including Tokachi nagaha?wdd01252?,Mercury?wdd01991?,Xihuangdou-9?ZDD14911?and 14 accessions with high drought tolerance in grade 2,including GR8836?wdd01594?,Muyangchunheidoubing?ZDD03842?,Pengshanhuangkezi-3?ZDD21030?,etc.The drought tolerance of 247 mini core collection at adult stage were evaluated in Yazhou,Sanya,Hainan province during 2017-2018,2018-2019.The seed weight per plant,pods per plant,plant height under drought stress condition decreased significantly compared with that under normal irrigation condition,and the difference were significant among genotypes.There was a significant positive correlation between drought resistance coefficient?DC?and weighted drought resistance coefficient?DWC?.Seven accessions with high-yield and drought-tolerant were screened by using maximin?minimax method,including Heihe 1?ZDD00041?,Dabaipi?ZDD02866?,Dalihuang?ZDD06363?,Yangtianxiaohuangdou?ZDD08190?,Chichenglvhuangdou?ZDD08238?,Shiyuehuang?ZDD12400?and Shifangluosidou?ZDD12836?.2.75 SNP markers controlling drought tolerance at germination and maturity stage by using genomewide association analysis.The genome-wide association analysis for drought tolerance-related traits at germination and adult stage was performed by using a mixed linear model?PCA+K?in TASSEL which employing 158327 SNP markers uniformly distributed on 20 chromosomes.A total of 26 SNPs with significant signal at germination stage were detected,including 8 for RGR,8 for RGE,22 for GDTI,5 for GSI and 8 for MFV.26 SNPs were distributed in 10 soybean chromosomes,and explaining 5.19⁹.66% of phenotypic variation.Nine SNPs,such as Gm20₃4956219,Gm20₃4956219,are associated with two or more than two tolerance-related traits;Nine SNP markers were located in or near regions where QTLs related to drought tolerance have been previously mapped by linkage analysis.Five SNPs associated with drought tolerance were detected for the first time and and 41 genes that may control drought tolerance at germination stage were identified.Forty-nine SNPs associated with drought tolerance at adult stage were detected,including 23 for yield,15 for DC and 13 for DWC.49 SNPs were distributed in 18 soybean chromosomes,and explained 7.08⁴7.23% of phenotypic variation.Ten SNPs,such as Gm01₁0000937 and Gm01₃1287639,are associated with two tolerance-related traits;Ten SNP markers were located in or near regions where QTLs related to drought tolerance have been previously mapped by linkage analysis,and 86 genes controlling yield and drought tolerance were identified.These results will enrich our genomic understandings of drought tolerance,and provide molecular and material support for MAS in soybean breeding.