CANDIDATE GENE ANALYSIS OF QUANTITATIVE DISEASE RESISTANCE IN WHEAT

¹ Department of Plant Pathology, Throckmorton Plant Sciences Center, Kansas State University, Manhattan, KS 66506 USA

² Department of Agronomy, Nanjing Agricultural University, Nanjing, 210095, P. R. China

In recent years, advances in plant-microbe interactions and genome mapping have lead to increased understanding of genes involved in plant defense and quantitative disease resistance. Here, we report on the application of the candidate gene approach to the mapping of QTL for disease resistance in a population of wheat recombinant inbreds. Over 50 loci representing several classes of defense response (DR) genes were placed on an existing linkage map and the genome was surveyed for QTL associated with resistance to several diseases. Analysis revealed QTL with large effects in regions of putative resistance genes. Several candidate genes, including oxalate oxidase, peroxidase, superoxide dismutase, chitinase, and thaumatin mapped within previously identified resistance QTL and explained a greater amount of the phenotypic variation. A cluster of closely linked DR genes on the long arm of chromosome 7B, which included genes for catalase, chitinase, thaumatins, and an ion channel regulator, had major effects for resistance to leaf rust of adult plants under conditions of natural infestation. The results of this study indicate that many minor resistance QTL may be the action of DR genes, and that the candidate gene approach can be an efficient method of QTL identification.