Utilization of tall wheatgrass translocation lines to improve fusarium head blight resistance in wheat

Fusarium head blight (FHB) and leaf rust (LR) are two major fungal pathogens threatening the wheat crop, consequently identifying resistance genes from various sources is always of importance to wheat breeders. Type II FHB resistance in wheat has been improved by introgressing QTL from landraces and wild species. The present study was undertaken to (1) combine two different type II FHB resistance QTL in the backgrounds of six adapted wheat lines (2) improve the map resolution of Qfhs.pur-7EL. In the first objective, the FHB resistance gene Fhb1 originated in a Chinese wheat cultivar and is located on wheat chromosome 3BS, and Qfhs.pur-7EL was introgressed from tall wheatgrass onto wheat chromosome 7DL were combined in six adapted wheat lines. The effect of pyramiding resistance genes through marker-assisted selection was assessed by scoring plants for disease development after inoculating with a combination of four different local FHB isolates. The response of 6 populations of pyramided lines was evaluated in both greenhouse and transplant nursery. The pyramided lines as well as Fhb1-only lines exhibited high levels of resistance to the mixture of four FHB isolates. Although Fhb1 or Qfhs.pur-7EL alone is strong enough to achieve satisfactory resistance, pyramided lines may be more stable over time. In the second objective, we identified tightly linked markers for FHB-resistance QTL Qfhs.pur-7EL and the LR-resistance gene Lr19 using genotyping by sequencing in a wheat-tall wheatgrass introgression-derived recombinant inbred line (RIL) population. 216,318 SNPs were discovered for this population. After filtering, 1700 high-confidence SNPs were used to conduct the linkage and QTL analysis. Qfhs.pur-7EL was mapped to a 2.9 cM region within a 43.6 cM segment of wheatgrass chromosome 7el 2 that was translocated onto wheat chromosome 7DL. The LR gene Lr19 from 7el1 was mapped to a 1.21 cM region in the same area, in repulsion. Five lines were identified with the resistance-associated SNP alleles in coupling for Qfhs.pur-7EL and Lr19. Investigation of the genetic characteristics of the parental lines of this RIL population indicated that they are translocation lines in two different wheat cultivar genetic backgrounds instead of 7E-7D substitution lines in Thatcher wheat background as previously reported in the literature. The wheat lines containing pyramided FHB resistance genes and pyramided FHB and LR resistance genes: Qfhs.pur-7EL and Lr19, developed and identified in this study, show potential as genetic resources for sustainable wheat production in areas affected by Fusarium head blight and leaf rust diseases