Genome Wide Association Analysis of Leaf Rust Response in a Worldwide Germplasm Collection of Durum Wheat

Leaf rust (caused by Puccinia triticina Eriks.) is increasingly impacting durum wheat production worldwide since the recent emergence of races with virulence to widely grown cultivars in many durum production areas. A leaf rust race highly virulent on durum wheat was recently collected in Kansas. This race may spread to the Northern Great Plains, where most of the U.S. durum wheat is produced. The objective of this study was to identify sources of resistance to North American (USA and Mexico) leaf rust races at seedling stage in the greenhouse and at adult stage in field experiments. Genome wide association analysis was used to identify SNP markers associated with leaf rust response in a worldwide durum wheat collection of 496 accessions. Ten accessions comprised of six landraces, two breeding lines, and two cultivars were resistant across all experiments. Association mapping revealed 91 significant SNPs associated with leaf rust response. Of these 91 SNPs, 33 were located on chromosomes 2A and 2B. The leaf rust – SNP associations were distributed across all chromosomes except for 1B. Twenty three markers were associated with leaf rust response at seedling stage experiments, while 68 markers were associated with leaf rust response at adult stage. The current study identified a total of 22 novel loci associated with leaf rust response in durum wheat. The discovery of these novel loci through association mapping is a significant step in availing useful genes that can be used to broaden leaf rust resistance in durum wheat germplasm.