Molecular mapping determines that Hessian fly resistance gene H9 is located on chromosome 1A of wheat.

Hessian fly [ Mayetiola destructor (Say)] is one of the major insect pests of wheat ( Triticum aestivum L.) worldwide. Hessian fly resistance gene H9 was previously reported to condition resistance to Hessian fly biotype L that is prevalent in many wheat-growing areas of eastern USA and an RAPD marker, OPO051000, linked to H9 in wheat was developed using wheat near-isogenic lines (NILs). However, marker-assisted selection (MAS) with RAPD markers is not always feasible. One of the objectives in this study was to convert an RAPD marker linked to the gene H9 into a sequence characterized amplified region (SCAR) marker to facilitate MAS and to map H9 in the wheat genome. The RAPD fragment from OPO051000 was cloned, sequenced, and converted into a SCAR marker SOPO05909, whose linkage relationship with H9 was subsequently confirmed in two F2 populations segregating for H9. Linkage analysis identified one sequence tagged site (STS) marker, STS-Pm3, and the eight microsatellite markers Xbarc263, Xcfa2153, Xpsp2999, Xgwm136, Xgdm33, Xcnl76, Xcnl117 and Xwmc24 near the H9 locus on the distal region of the short arm of chromosome 1A, contrary to the previously reported location of H9 on chromosome 5A. Locus Xbarc263 was 1.2 cM distal to H9, which itself was 1.7 cM proximal to loci Xcfa2153, Xpsp2999 and Xgwm136. The loci Xgwm136, Xcfa2153 and SOPO05909 were shown to be specific to H9 and not diagnostic to several other Hessian fly resistance genes, and therefore should be useful for pyramiding H9 with other Hessian fly resistance genes in a single genotype. [ABSTRACT FROM AUTHOR]