Screening Of Germplasm And Genome-wide Association Analysis For Resistance To Crown Rot And Fusarium Head Blight In Wheat

Wheat is one of the most important food crops in the world.The safety of global wheat production has been threatened by various fungal diseases for a long time.Crown rot(CR)and Fusarium head blight(FHB)are fungal diseases of wheat caused by Fusarium spp.,which are easy to cause serious loss of wheat yield and quality.In recent years,CR and FHB are common in the main wheat producing areas in China and has been increasing year by year,which seriously threaten the safety of wheat production in China.Planting resistant varieties is the most economical and effective way to control diseases.Excellent resistance sources and genes are the basis of disease resistance breeding.However,because the CR or FHB resistance in wheat is a quantitative trait with complex genetic basis and is easily affected by environment,there are some difficulties in the identification and utilization of resistance sources and resistance genes.At present,no wheat varieties or germplasms immune to CR and FHB have been found,and there is a great lack of resistance sources and resistance genes that can be used in breeding.It is urgent that more resistant germplasms and new genes were developed to expand the genetic basis of CR and FHB resistance and to breed resistant cultivars,especially excellent sources with resistance to both disease.In this study,578 wheat germplasms representing genetic diversity were used to identify and evaluate their resistance to CR and FHB simultaneously.The aim of this study was to screen excellent resistance sources and to develop CR and FHB resistance loci using by genome-wide association study(GWAS).The results are as followed:1.Seven and eighty germplasms were classified as resistant(R)and moderately resistant(MR)to CR,and accounting for 1.29% and 13.8%,respectively.The resistant cv.included Zimai 12,Xinong 509 and landrace Mazhamai from Huang-huai winter wheat area,Sifangmai from southwest winter wheat area,Huxumai from winter wheat area in the middle and lower reaches of the Yangtze River,Romanian from Italy and Dawson from Canada.The disease index(DI)of Zimai 12 and huxumai were lower than that of control cv.Sunco(DI = 11.5).In addition,18 germplasms were classified as R or MR in two years showing stable resistance to CR.These cv.included Xibei 612,Liaomai 16,Heng 6632,Zhengmai 9045 and Zhongyu 12 in Huang-huai winter wheat area,Zhenmai 168 in the winter wheat area of middle and lower reaches of Yangtze River,cultivar Mianyang 26 and landrace Yuqumai in southwest winter wheat area,Jichun 1016 in northeast spring wheat area,cultivar Sirmione and Ailiduo in Italy,cultivar opata and breeding line Ron 2-Fnd×CMH74A.630 in Mexico,American cultivar Owens,freedom,vaiolet,Moroccan cultivar aguilal..2.Two and thirty-two germplasms were classified as resistant(R)and moderately resistant to FHB were selected.The disease resistance varieties(breeding lines)included Zhengmai 9201 and Lumai 5from Huang-huai winter wheat area.The DI of Zhengmai 9201 and Lumai 5 were 3.6-16.6 and 6.7-12.5 respectively,showing stable resistance to FHB.There are 32 varieties(breeding lines)with moderate resistance(7.5%)These germplasms included Pingyuan 50,Yangguang 851,Xuke 718,Jinan 17,Yumai 54(Bainong 64),Zhengnong 17,Yumai 19,Fengchan 1,Zhongxin 78,Xinong 528,Yumai 2(Baofeng 7228),Luomai 906,Luomai 4,Xiaoyan 4,Jimai 19,Zhengmai 9405,Bainong 207,breeding line 935106 from Huang-huai winter wheat area,the varieties of Shijiazhuang 54,Zhongmai 175,Fengkang 8,Jingdong 22,Jimai 38 xinxi and kenong 199 from the northern winter wheat area,Wanmai 50,Ningmai 9 and xinfumai 1 from winter wheat area in the middle and lower reaches of the Yangtze River,Chuanmai 104 and Mianyang 20 from the southwest winter wheat region,Hongmai from spring and winter wheat areain Qinghai-Tibet,Dromedaris from South Africa,Gaboto from Argentina,These varieties(breeding lines)were classified as resistant(R)or moderately resistant(MR)to FHB in different environmental identification,DI was lower than40.3.Nine germplasms were classified as resistant(R)or moderately resistant(MR)to CR and FHB in different environmental identification,included Luomai 906,Zhengmai 9405,landrace Pingyuan 50,breeding line 935106 from Huang-huai winter wheat area,Chuanmai104 and Mianyang 20 from southwest winter wheat area,Jingdong 22 and Jimai 38 from north winter wheat region,and Dromedaris from South African.4.The whole genome association analysis showed that 17 SNPs were significantly correlated with CR seedling resistance in 2019,which were located on 1D,2B,2D,4A,5A,7A,7B and 7D chromosomes respectively.In 2020,32 SNPs were significantly related to CR seedling resistance,which were located on 1B,1D,2B,3A,3D,4A,4B,4D,5A,5D,7A,7B and 7D chromosomes.Among them,the stable associated SNPs were AX-94739307 on chromosome 2B,AX-94544187 on 4A,AX-111044795 and AX-109855826 on 7B,and AX-111463977 and AX-95195877 on 7D.5.The whole genome association studies showed that 20 SNPs were significantly correlated with FHB resistance in 2019,which were located on 2D,4A,5B,and 6A chromosomes respectively;17 SNPs were significantly related to FHB resistance in 2020,respectively on 2D,3B,3D,4B,5A,6B,7B and 7D chromosomes.Among them,only the SNPs located on the 2D chromosome,AX-109261081,AX-109755068 and AX-109891310,showed stable expression,indicating that there might be a QTL related to FHB resistance in this interval.