Identification and mapping of H32, a new wheat gene conferring resistance to Hessian fly.

H32 is a newly identified gene that confers resistance to the highly pervasive Biotype L of the Hessian fly [ Mayetiola destructor (Say)]. The gene was identified in a synthetic amphihexaploid wheat, W-7984, that was constructed from the durum 'Altar 84' and Aegilops tauschii. This synthetic wheat is one of the parents of the marker-rich ITMI population, which consists of 150 recombinant inbred lines (RILs) derived by single-seed descent from a cross with 'Opata 85'. Linkage analysis of the H32 locus in the ITMI population placed the gene between flanking microsatellite (SSR) markers, Xgwm3 and Xcfd223, at distances of 3.7 and 1.7 cM, respectively, on the long arm of chromosome 3D. The Xgwm3 primers amplified codominant SSR alleles, a 72 bp fragment linked in coupling to the resistance allele and an 84 bp fragment linked in repulsion. Primers for the SSR Xcfd223 amplified a 153 bp fragment from the resistant Synthetic parent and a 183 bp fragment from the susceptible Opata line. Deletion mapping of the flanking Xgwm3 and Xcfd223 markers located them within the 3DL-3 deletion on the distal 19% of the long arm of chromosome 3D. This location is at least 20 cM proximal to the reported 3DL location of H24, a gene that confers resistance to Biotype D of the Hessian fly. Tight linkage of the markers will provide a means of detecting H32 presence in marker-assisted selection and gene pyramiding as an effective strategy for extending durability of deployed resistance.