Genome-wide Association Study Of Resistance To Stripe Rust In Foreign Wheat Germplasm

Common wheat(Triticum aestivum L.)is the important crops in China.The problem of the safe production of wheat directly affects the food security of our country.Fungal diseases have always been an important factor restricting yield of wheat.Wheat stripe rust is the most serious diseases affecting wheat production in China,and the epidemic year can cause 20%-30% yield loss.Cultivating and planting disease-resistant varieties is the most economical and environmentally friendly method.However,due to the rapid mutation of Puccinia striiformis races,new physiological races are often produced and the disease resistance genes lose their resistance.Especially the Yr26-virulent Pst race(V26)group overcomes almost all currently deployed resistance genes in China and has continued to accumulate new virulence in recent years.Therefore,discovering new sources of resistance is significative for diversification and the rational deployment of resistance genes in the future.More than 2000 wheat germplasm were collected from the worldwide.Among them,410 exotic wheat germplasm were undeveloped,which may have potential resistance gene resources.This panel was genotyped using high-density wheat 660 K SNP array and phenotypic evaluation for YR resistance.Based on these genotype and phenotype data,we carried out the genome-wide association study to find effective disease resistance sites.Meanwhile we created many genetic groups to verify the accuracy of the genome-wide association analysis results in the future.Among them,we selected elite resistance cultivars S76 hybridized with jinmai79 to construct F2:3 population for preliminary analysis of resistance to stripe rust.The main results of this study were as follows:1.The 410 wheat materials collected from the worldwide been challenged by 10 stripe rust races in seedling stage and stripe rust for three-year in Yangling,Tianshui and Jiangyou in adult plant stage.It is found that 43 materials show resistance in all-stage,which could create genetic population and identified by genetic analysis.2.Combined with 660 K SNP chip genotyping data,genome-wide association analysis of seedling resistance to stripe rust was implemented.35 loci conferring resistance were identified and distributed on chromosome 1A,1B,1D,2A,2B,2D,3A,3B,4A,4B,5A,5B,5D,6A,6B,6D,7A,7B and 7Dand explained phenotypic variances ranged from 53 to 75%.Of these,14 were co-located in the proximity of the known loci including catalogued Yr genes Yr9,Yr10,Yr26,Yr33,Yr47,Yr56,Yr57,Yr64,Yr67,Yr72 and Yr81 and seven of them were confirmed.Other loci that were identified to be different from reported Yr genes need further confirmation.Nine QTL with significantly large phenotypic effect on resistance to all races were considered as major loci for resistance.The identified loci enrich our stripe rust resistance gene pool and the linked SNPs should be useful for marker-assisted selection in breeding programs.3.Wheat cultivar S76 was susceptible to stripe rust in the seedling stage,but showed stable resistance in adult stage.F2 and F2:3 lines were developed from a cross between S76 and Jinmai 79.660 K SNP chips were implemented to bulked pools and their parents to identify SNPs asszociated with the major QTL.Analysis,compared to other chromosomes,chromosome 2A,4B and 7D differential SNP loci(1713,388 and 134)accounted for a higher proportion of parental differential chromosome loci,which were 25.8%,5.7% and 3.4%,respectively.It was speculated that there may be resistance loci on 2A,4B and 7D.At the same time,the functional markers developed based on Yr18 were tested for S76,and the results were positive,indicating that S76 contained Yr18.Moreover,S76 showed a dry leaf tip phenotype,so it was speculated that the resistance loci on chromosome 7D was Yr18.It shows that the method of fast gene location by combining BSA with chip is reliable.