A Breeder-friendly Marker for the Eyespot Resistance Gene Pch1

Wheat of northwestern Europe and the Pacific Northwest (PNW) of the United States is prone to attack by the fungal pathogens Oculimacula yallundae and O. acuformis which cause the disease eyespot (strawbreaker footrot).  Up to 50% yield loss can occur with severe infections.  The most economical control for this disease is to employ cultivars carrying the resistance gene Pch1, introgressed from wheat relative Aegilops ventricosa.  An isozyme marker for the gene Ep-D1, a D-genome endopeptidase, has been shown to be completely linked to Pch1. PCR-based markers developed for Pch1 have either been 0.5 to 1 cM distant from Pch1, not genome specific, and/or require costly capillary electrophoresis systems such as ABI Prism DNA sequencers.  This study aimed to develop a breeder-friendly, economical, PCR-based marker linked to Pch1. Using primers designed to an EST encoding an Ep-D1 candidate gene (oligopeptidase B), ~750bp sequences were amplified cloned and sequenced from multiple wheat cultivars, aneuploid stocks, and diploid relatives.  Through sequence comparison, putative genome assignations were made for each of the clones.  Primers were designed to specifically co-amplify the D- and D^V-genome oligopeptidase B sequences.  Length polymorphisms between the two amplicons provide a genome-specific, codominant, polymorphic marker easily visualized by electrophoresis on agarose gels.  Use of this marker should improve genotypic selection for Pch1 resulting in the reduction of yield loss by this disease due to the deployment of eyespot-resistant cultivars in the future.