Precise Mapping Of A Major QTL Qfh.njau-2B Associated With Fusarium Head Blight Resistance In Bread Wheat

Fusarium head blight(FHB)is a devastating disease in wheat,and exploiting resistance genes to breed resistant varieties is the most cost-effective solution to control this disease.Many FHB resistance QTLs have been mapped to date,but only a few were deeply studied,which cannot meet the demand of resistance breeding in practice.In the previous studies,a major QTL Qfh.njau-2B was identified for the FHB resistance of Type ?(against initial infection)and Type ?(against fungal spread within spike)in the Nanda2419 x Wangshuibai mapping population consisting of 136 recombinant inbred lines(RILs),with the favorable allele from the founder cultivar Nanda2419.The present study reported the precise mapping of Qfh.njau-2B.The Nanda2419 x Wangshuibai mapping population,which was enlarged to 530 RILs,was used to construct a high-density genetic map of the Qfh.njau-2B region.The map spanned 18.2 cM and included 28 polymorphic markers,5 of which were newly developed.A total of 137 lines recombinating within the Qfh.njau-2B interval were identified in the RIL population using the flanking markers Xwmc474 and Xmag1729.Markers linked with other resistance QTLs in the RIL population were used in counter-selection to generate homozygous loci associated with the susceptibility to FHB.Finally,22 recombinants related with Type ? resistance representing 12 gentoypes and 24 recombinants related with Type ? resistance representing 14 genotypes,carrying no other resistance QTLs of FHB,were obtained through genotyping with 26 markers mapping to the Xwmc474-Xmagl729 interval.These recombinants were evaluated in three field trials and their resistance performance showed significant differences according to phenotypes between the resistant group and susceptible group,for each of Types ? and Type ?.According to the genotypes and phenotypes of these recombinants,Qfh.njau-2B associated with Type ? and Type ? resistance,respectively,was mapped to 5.1-cM interval flanking by Xwmc499 and Xgwm47.4 and 3.4-cM interval flanking by Xwmc499 and Xzmh530.In addition,119 landraces were phenotyped in multiple field trials and genotyped with a 90k Illumina Wheat Single Nucleotide Polymorphism(SNP)Chip.Association mapping analysis revealed 17 SNPs on chromosome 2B associated Type ? resistance,including 14 SNPs within the Qfh.njau-2B interval,with the most significant marker 1.63 cM away from the Xwmc499(P<10-7).The sequence information of mapped markers and their contigs in the URGI database was used to determine the colinearity of Qfh.njau-2B region with rice and Brachypodium genomes.Comparative genomics analysis showed that the marker order is conserved between wheat,rice and Brachypodium in the Qfh.njau-2B region,and that this region corresponded to a?9 Mb region in chromosome 4 of rice and a?9Mb region in chromosome 5 of Brachypodium.