Identification of QTL for Resistance to Ug99 Races of Stem Rust in Durum Wheat

Stem rust of durum wheat (Triticum turgidum L. var. durum) caused by Puccinia graminis f. sp. tritici has the potential to cause major yield losses around the world, particularly with emergence of new races such as Ug99 and its derivatives, including race TTKSK. The present study was conducted to identify genomic regions associated with stem rust resistance using a doubled haploid mapping population derived from a cross between the cultivar Strongfield, (moderately susceptible to the Ug99 stem rust race group) and line A9919-BY5C (resistant to the Ug99 race group). The parents and population were phenotyped for adult plant stem rust severity and infection response in Kenya from 2008 to 2011, and for seedling reaction to TTKSK in a containment facility near Morden, Manitoba in 2010. Composite interval mapping on 66 doubled haploid families using 612 SNP/DArT markers identified four significant QTL associated with stem rust resistance. A QTL on chromosome 6A associated with seedling resistance was derived from resistant parent A9919-BY5C and explained 71% of Phenotypic Variation (PV). Another QTL derived from A9919-BY5C was located on chromosome 1B and explained 14% PV. Quantitative trait loci on chromosomes 4A and 5B were not stable across years and were derived from Strongfield. Markers associated with the QTL can be used to proactively assist with the incorporation into Canadian durum wheat cultivars resistance to the Ug99 stem rust race group.