GENETIC-MAPPING OF HESSIAN FLY AVIRULENCE GENE VH6 USING BULKED SEGREGANT ANALYSIS

The Hessian fly, Mayetiola destructor (Say), an important insect pest of wheat, Triticum aestivum L., has a gene-for-gene relationship with wheat: single genes in the insect condition avirulence to specific res istance genes in wheat. We report the discovery of the first molecular genetic marker that is tightly linked to a Hessian fly avirulence gen e. This dominant DNA polymorphism (OPG15-1) was identified using bulke d segregant analysis and arbitrary primers in polymerase chain reactio ns. Bulked segregant analysis was modified to accommodate the anomalou s chromosome cycle of the Hessian fly. It was used to identify DNA pol ymorphisms linked to the gene (vH6) that confers avirulence to the res istance gene H6 in wheat. OPG15-1 was cloned and sequenced, and a pair of site-specific primers were designed that converted it into a codom inant single-stranded conformational polymorphism. Both OPG15-1 and vH 6 were shown to be X-linked, and the genetic distance between the two loci was 2.5 +/- 2.5 cM. In situ hybridization to polytene chromosomes of larval salivary glands indicated that OPG15-1 resides near the cen tromere of Hessian fly chromosome X1.