Genomic manning of defense response genes in wheat

Defense response (DR) genes are a broad class involved in plant defense. In this study we mapped 36 probes representing seven classes of defense respo nse genes. This collection of probes represents genes involved in the hyper sensitive response (HR), pathogenesis-related (PR) genes, genes for the fla vonoid metabolic pathway, genes encoding proline/glycine-rich proteins, ion channel regulators, lipoxygenase, lectin, and others. Using nullisomic-tet rasomic lines of 'Chinese Spring', we were able to assign at least 167 loci to the 21 chromosomes of wheat. Homoeologous group 7 chromosomes possessed the most DR loci followed by group 2. Sixty-two loci were placed on existi ng genetic linkage maps of wheat. Map locations indicated that the DR gene loci are not randomly distributed throughout the wheat genome, but rather a re located in clusters and/or in distal gene-rich regions of the chromosome s. Knowledge of the chromosomal locations and genome organization of DR gen es will be useful for candidate gene analysis of quantitative trait loci.