Wheat Fusarium head blight (FHB) is one of the most destructive diseases of wheat and causes significant yield and quality losses in wheat worldwide. Using resistant cultivars is one of the most effective approaches to control FHB. Although more than 600 quantitative trait loci (QTLs) have been reported, most of them showed minor effects and not consistent across environments. To explore new sources of resistance, an EMS-induced mutant population derived from an FHB moderately susceptible hard winter wheat cultivar ‘Jagger’ was screened for FHB resistance. One mutant line (JagMut1095) showed significantly higher FHB resistance than Jagger (P < 0.001), with mean percentage of symptomatic spikelets (PSS) in a spike of 32% for JagMut1095 and 69% for Jagger. A population of 154 recombinant inbred lines (RILs) was developed from the cross of JagMut1095 x Jagger and was used for QTL analysis on FHB resistance in four greenhouse environments. A total of 3,757 high quality GBS-SNPs were mapped on 21 wheat chromosomes using recombinant inbred lines (RILs), and 1,003 unique SNPs were mapped to 22 linkage groups corresponding to the 21 chromosomes after binning the SNPs in the same positions. The map is 3,106 cM in genetic length with a marker density of 3.1 cM per marker. Composite interval mapping identified 12 QTLs for Type II FHB resistance on chromosomes 1B, 2B, 3A, 4B, 4D, 5A, 5B, 5D, 6A, 6B, 7A and 7B. Among them, four QTLs on chromosomes 3A (QFhb.hwwg-3AS), 4B (QFhb.hwwg-4BS), 5A (QFhb.hwwg-5AL) and 7A (QFhb.hwwg-7AS) were repeatable in at least two environments. QFhb.hwwg-5AL was repeatable in all environments and for the best linear unbiased estimated (BLUE) values, and QFhb.hwwg-3AS was repeatable in three of the four environments (2019S, 2019F and 2020S). These two QTLs had the resistance alleles from the mutant and explained up to 11.3% and 14.5% of the phenotypic variation, respectively. QFhb.hwwg-4BS and QFhb.hwwg-7AS were both detected in three environments (2018F, 2019S and 2020S) and by the BLUE values, and Jagger contributed resistance alleles at both loci. QFhb.hwwg-4BS showed the largest effect on FHB resistance and explained up to 32.8% of the phenotypic variation, therefore, was chosen for fine mapping. This QTL was delimited to a 1.5 Mb interval on 4BS carrying 17 high confidence genes including Rht1, a ‘Green Revolution’ reduced height gene. QFhb.hwwg-4BS overlaps with the major QTL QPh.hwwg-4BS for plant height, thus, QPh.hwwg-4BS is most likely Rht-1B. Map-based cloning and molecular characterization of the resistance mechanisms underlying QFhb.hwwg-4BS will facilitate determination of the gene identity and effective deployment of the resistance QTL in breeding.
ACKNOWLEDGEMENT AND DISCLAIMER
This material is based upon work supported by the U.S. Department of Agriculture. This is a cooperative project with the U.S. Wheat & Barley Scab Initiative. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture. USDA is an equal opportunity provider and employer.