Genome-wide Association Study(GWAS) For Salt Tolerant Traits At Seedling Stage In Wheat

Soil salinization is one of the main abiotic stress factors affecting agricultural production worldwide and salt tolerance has a signficant effect on plant growth and development.Wheat is the main cultivated crop in salinized soil.It plays an important role in the improvement and utilization of saline-alkali land.Screening and utilizing salt-tolerant germplasm resources and mining salt-tolerant genes play an important role in the transformation,utilization of saline-alkali land and in improving the agricultural production level of saline-alkali land.In this study,two trials were carried out with three NaCl concentrations(T1:0 mM(CK),T2:75mM and T3:150 mM NaCl)at seedling stage using a variety population(VP)comprise of125 wheat varieties,which planted latterly in the Yellow and Huai River Valley Facultative WinterWheatRegion.A number of ten seedling traits including shoot height(SH),root length(RL),root number(RN),root fresh weight(RFW),shoot fresh weight(SFW),root dry weight(RDW),shoot dry weight(SDW),total dry weight(TDW),ratio of root and shoot dry weight(RSDW)and ratio of root and shoot fresh weight(RSFW)were mensurated.Combining with the9329 SNP(single nucleotide polymorphism)sites that screened by 90 K SNP chip,genome-wide association study(GWAS)was conducted for salt-tolerant traits at seedling stage in order to find the significant correlation sites.The results should helpful for further study on the isolation of related genes and the marker-assisted selection(MAS)of salt tolerance in wheat breeding programs.The main results are as follows:(1)Phenotypic variation analysis showed that ten traits showed significant differences in six environments,the range of variation coefficientsranged from 10.69%(E2T3)to 49.82%(E1T3).All of the ten traits showed continuous variation.Analysis of variance(ANOVA)showed that there were significant differences among genotypes of all the ten traits.The broad-sense heritabilities were all over 65%(65.54%-83.03%).Correlation analysis showed that the most traits were positively correlated.(2)A total of 268 QTLs were detected to be significantly correlated with salt-tolerant traits and salt-tolerant index at seedling stage,including 292 SNP markers with 247 markers which were located previously on specialchromosomes.The marker R~2 ranged from 8.95%to26.84%.The QTLs distributed on 19 chromosomes except for 3D and 5D.(3)A numberof 108 RHF-QTLs were detected to be significantly correlated with salt-tolerant traits,including 174 SNP markers with 150 markers which were located previously on specialchromosomes.The marker R2 ranged from 8.95%to 6.84%.The QTLs distributed on 17 chromosomes except for3D,5D,6D and 7D.Chromosome 1B contains the most markers(40)followed by chromosome 7B(17).(4)For salt-tolerant index,a total of 119 RHF-QTLs were detected,including 203 SNP markers with 172 markers which were located previously on specialchromosomes.The marker R~2 ranged from 9.15%to 24.84%.The QTLsdistributed on 19 chromosomes except for 3D,5D and 7D.Chromosome 1B contains the most markers(37)followed by chromosome3B(20).(5)A total of 26 QTL clusters included 93 QTLs were found on the 12 chromosomes,1A,1B,1D,2A,2B,3A,3B,4A,5A,6B,7A and 7B.Among them,twoQTL clusters(including 8QTLs)were not located on the chromosome.