Molecular Mapping of Stripe Rust Resistance in Hard Red Winter Wheat TAM 111 Adapted to the U.S. High Plains

Stripe rust, also known as yellow rust, caused by Puccinia striiformis Westend. f. sp. tritici Erikss. (Pst), is one of the most important foliar diseases of wheat (Triticum aestivum L.) in the United States and other parts of the world. To investigate the genetic basis of resistance conferred by the winter wheat cultivar 'TAM 111', a mapping population of 124 F-5 and F-6 derived recombinant inbred lines (RILs) developed from the cross of 'TAM 112'/TAM 111 was evaluated against Pst populations in eight environments in the United States and against predominant race PST-100 in the greenhouse. The RIL population was further genotyped with Diversity Arrays Technology, simple sequence repeats and sequence tagged sites markers. A major quantitative trait locus (QTL), QYr.tam-2BL, was identified on the long arm of chromosome 2B, which is found to be associated with resistance to stripe rust in TAM 111. QYr.tam-2BL was identified in five out of the eight environments (Arkansas 2012, Arizona 2010, Castroville, TX, 2010, Mt. Vernon, WA, 2010 and Pullman, WA, 2011) as well as in the greenhouse, and explained 13 to 63% of the total phenotypic variation in severity across the environments. The QTL was also detected in seedling and adult plant stages with race PST-100 under controlled greenhouse conditions. Based on the available evidence, QYr.tam-2BL probably represents a previously uncharacterized gene on 2BL. Minor QTL on chromosomes 1A, 2A, 6B, and 7D were also detected inconsistently across environments. Because the effectiveness of QYr. tam-2BL was observed to be environmentally dependent and probably race-specific, it is suggested to combine this locus with effective major genes or adult plant resistance genes to increase its usefulness.