Mapping of Leaf Rust Resistance Loci in Two Kenyan Wheats and Development of Linked Markers.

Leaf rust caused by the pathogen () is a destructive fungal disease of wheat that occurs in almost all wheat-growing areas across the globe. Genetic resistance has proven to be the best solution to mitigate the disease. Wheat breeders are continuously seeking new diversified and durable sources of resistance to use in developing new varieties. We developed recombinant inbred line (RIL) populations from two leaf rust-resistant genotypes (Kenya Kudu and AUS12568) introduced from Kenya to identify and characterize resistance to and to develop markers linked closely to the resistance that was found. Our studies detected four QTL conferring adult plant resistance (APR) to leaf rust. Two of these loci are associated with known genes, and , residing on chromosomes 1B and 7B, respectively. The remaining two, and , contributed by Kenya Kudu and AUS12568 respectively, are putatively new loci for resistance. Both and were found to interact additively with in significantly reducing the disease severity at adult plant growth stages in the field. We further developed a suite of six closely linked markers within the locus and four within the region. Among these, markers and , flanking , and , distal to , were identified as the most closely linked and reliable for marker-assisted selection. The markers were validated on a selection of 64 Australian wheat varieties and found to be polymorphic and robust, allowing for clear allelic discrimination. The identified new loci and linked molecular markers will enable rapid adoption by breeders in developing wheat varieties carrying diversified and durable resistance to leaf rust.