Mapping of Defense Response Gene Homologs and Their Association with Resistance Loci in Maize

Defense response genes in higher plant species are involved in a variety of signal transduction pathways and biochemicalreactions to counterattack invading pathogens.In this study,a total of 366 non-redundant defense response gene homologs(DRHs),including 124 unigenes/expressed sequence tags,226 tentative consensuses,and 16 DRH contigs have beenidentified by mining the Maize Genetics and Genomics and The Institute for Genomic Research maize databases using 35essential defense response genes.Of 366 DRHs,202 are mapped to 152 loci across ten maize chromosomes via both thegenetic and in silico mapping approaches.The mapped DRHs seem to cluster together rather than be evenly distributedalong the maize genome.Approximately half of these DHRs are located in regions harboring either major resistancegenes or quantitative trait loci(QTL).Therefore,this comprehensive DRH linkage map will provide reference sequencesto identify either positional candidate genes for resistance genes and/or QTLs or to develop makers for fine-mapping andmarker-assisted selection of resistance genes and/or QTLs.