Identification Of Stress-tolerant Germplasm Resources And Elite Alleles In Wheat

Wheat(Triticum aestivum L.)is one of the three major cereal crops worldwide,developing wheat varieties with wide adaptability is an economical and effective strategy to cope with global climate change and ensure food security.However,the selection of elite parental lines and the efficiency of molecular breeding are hindered by limited resources of stress-tolerant germplasm and alleles.Therefore,Identification of stress-tolerant germplasm and elite alleles is a key task for wheat improvement.In the present study,three kinds of wheat population,i.e.natural population,doubled haploid population and derived population were used to investigate the physiological and yield traits under multiple stress conditions,including drought,heat and salt stress.The stress tolerance of wheat accessions was identified by the comprehensive evaluation indices.The genotypes of all accessions were detected using wheat 660K SNP array.The stress-tolerant alleles were identified with the methods of genome-wide association study(GWAS)and linkage mapping.The main results were as follows:1.Based on the comprehensive evaluation indices,21 accessions with high drought tolerance,24 accessions with high heat tolerance,16 accessions combined high drought and heat tolerance,and 24 accessions with high salt tolerance were selected.Nineteen accessions of them showed high tolerance under multiple stress conditions.2.One hundred and eighty-nine yield-related loci were detected by GWAS,32 of which were consistent across different environments;135 yield-related QTL were detected by linkage mapping,15 of which were overlapped with associated loci detected by GWAS.3.Total of 64,27 and 30 loci associated with drought tolerance,heat tolerance and combined drought and heat tolerance were detected by GWAS,respectively,six of which were associated with multiple stress tolerance.Forty-six drought and/or heat tolerance-related QTL were detected by linkage mapping,five of which were overlapped with associated loci detected by GWAS.4.One hundred and seventeen salt tolerance-related loci were detected by GWAS,27 salt tolerance-related QTL were detected by linkage mapping,five co-located loci were identified by combining the results of linkage mapping and GWAS.5.Five loci associated with yield-related traits and stress tolerance were identified,the favorable marker alleles or haplotypes in these loci were positively selected along with breeding process,which conversely diminished favorable genetic variation controlling stress tolerance in the same loci.6.Two salt responsive genes,TaRN1 and TaRN2 were identified in a haplotype block which was associated with salt tolerance coefficient of root number.TaRN1 were significant down-regulated by salt stress,whereas TaRN2 were significant up-regulated by salt stress,frameshift mutations caused by sequence deletion were observed in TaRN2 of salt-sensitive genotypes.In the present study,wheat germplasm with wide adaptability were identified,and the genetic basis of multiple stress tolerance were dissected.These results provide genetic resources and technical support for improving wheat by molecular breeding.