ICARDA引进-小麦苗期抗旱性的全基因组关联分析OA北大核心CSTPCD

[Objective]Drought is one of the most destructive environmental stresses limiting wheat production.The novel germplasm with excellent drought tolerance as well as their candidate loci were identified and characterized to enrich the genetic basis of drought tolerance and lay a material foundation for wheat genetic improvement in China.[Method]In this study,the drought tolerance of 198 wheat accessions introduced from International Dry Area Agriculture Research(ICARDA)were investigated at seedling stage through hydroponic method with PEG6000 simulating drought.Drought tolerance index(DTI)was calculated using the shoot fresh weight,root fresh weight,total biomass and root-shoot ratio,respectively.Genome-wide association analysis was performed using 660K SNP array genotyping to obtain the SNP loci and chromosome regions associating with drought tolerance index.Combined with the expression patterns in root and other tissues,the potential candidate genes were identified,and then they were further verified by qRT-PCR approach with the most drought-tolerant accession IR214 and the most drought-sensitive accession IR36 as materials.Finally,the excellent haplotypes of key candidate genes were analyzed.[Result]Compared to normal control condition,the growth and development of wheat were significantly impaired under drought treatment.There were also significant phenotypic variations among different accessions with all of the four traits displayed normal distribution.The coefficient of variation ranged from 0.363 to 0.760 with genetic diversity from 0.310 to 0.400.Using the weighted membership function value(D value),the drought tolerance of these accessions was evaluated.Results showed that accession IR214 had the highest D value with 0.851,followed by IR92,IR213,IR235,and IR218,which could be considered as the novel excellent drought-tolerance germplasm.Furthermore,through genome-wide association study(GWAS)analysis,a total of 102 loci were significantly associated with the DTI values based on these four traits,with the phenotypic variation explained value(PVE)from 1.07%to 38.70%,of which 60 loci were associated with above-ground fresh weight,1 locus associated with underground fresh weight,36 loci associated with biomass and the remaining 5 loci associated with root-shoot ratio.Then,31 candidate genes were predicated based on genomic annotation information and LD block.Combined with the expression patterns of them in roots and other tissues,4 candidates displaying differential expression between CK and drought conditions were obtained.Finally,the expression levels of these 4 candidates were further verified by qRT-PCR method with the most drought-tolerant accession IR214 and the most drought-sensitive accession IR36 as materials to obtain two key candidates associating with drought tolerance.Additionally,their haplotype effects were investigated.It was found that the different genotypes of AX-86174509 locus in TraesCS6A02G048600 gene showed significant differences in drought tolerance,which might be considered as a causal locus.[Conclusion]Totally,102 loci and 2 key candidate genes(TraesCS5B02G053500 and TraesCS6A02G048600)underlying drought tolerance at seedling stage were detected in ICARDA-introduced wheat,and AX-86174509 in TraesCS6A02G048600 was a potential functional locus.