Identification and Mapping of Resistance QTL for P. Triticina, P. Striiformis, Mayetiola Destructor and Lr18 in Soft Red Winter Wheat.

Leaf rust caused by Puccinia triticina and stripe rust caused by Puccinia striiformis are destructive pathogens of wheat (Triticum aestivum).  Host resistance is the most economical solution for providing full season control and reducing damage due to these diseases as opposed to use of multiple fungicide applications.  Pyramiding of multiple genes into single cultivars and use of quantitative trait loci (QTL) conferring adult plant resistance (APR) is the best strategy to achieve durable resistance.  The soft red winter wheat cultivar Jamestown is productive in the southern Corn Belt, the Deep South, and throughout the mid-Atlantic region.  This can be attributed to its combined resistance to leaf rust, stripe rust, and Hessian fly (Mayetiola destructor).  Phenotypic data was collected at diverse locations for resistance to leaf rust (NC, TX and VA) and stripe rust (AR, NC, GA, TX, and VA) in two primary mapping populations, Pioneer25R47 / Jamestown (P47/JT) and FG95195 / Jamestown (FG/JT) comprised of 170 and 186 F_8:9 recombinant inbred lines (RIL), respectively.  The P47/JT RILs and a set of 44 FG/JT RILS were genotyped with public 90K iSelect SNP array.  Initial analysis of the P47/JT population identified multiple putative resistance QTLs located on chromosomes 5B and 2B that are associated with leaf rust infection type and severity.  Variation explained by the putative leaf rust resistance QTL of Jamestown on 5B was as high as 25.0%, while 2B was 10.1%.  Initial results also identified QTLs for resistance on chromosomes 2B, 3A, and 5B associated with stripe rust infection type and severity in the P47/JT population.  The variation explained by putative stripe rust resistance QTL of Jamestown on 2B, 3A, and 5B was as high as 13.9%, 14.1%, and 20.6%, respectively.  Notably the leaf rust QTLs found on chromosome 5B are of significant interest as this chromosome is believed to contain gene Lr18.