Sex-linked inheritance of virulence against wheat resistance gene H9 in the Hessian fly (Diptera: Cecidomyiidae)

The dominant gen H9 in wheat, Triticum aestivum L., confers resistance to all known biotypes of Hessian fly, Mayetiola destructor (Say). Resistance is expressed as larval antibiosis (death of 1st instars). We isolated from a Washington (WA) population of Hessian files a virulent biotype capable of surviving on and stunting H9 wheat plants, and we established a genetic basis for the virulence. Analysis of F-1 and testcross progenies of reciprocal matings between the virulent WA biotype and avirulent Great Plains biotype indicated that the virulence trait is controlled by a single, completely recessive, sex-linked gene, which we designated a vH9. The inheritance pattern of virulence was consistent with previous genetic evidence that males are hemizygous and express only maternally derived sex chromosomes in their soma. Segregation analysis of the virulence locus with 2 sex-linked marker genes, white eye (w) and Isocitrate dehyrogenase (Idh), showed that vH9 assorts independently of Idh but is linked to w with 39.9 +/- 3.54% recombination. The results suggest that vH9 and eye color loci are located on 1 of the 2 sex chromosomes of the Hessian fly, and the Idh locus is on the other.