Identification and genomic location of resistance to bacterial leaf streak of barley

The bacterial leaf streak (BLS) disease of barley (Hordeum vulgare L.), caused by Xanthomonas translucens pv. translucens (Xtt), has become increasingly important worldwide in recent years. Inefficacy of chemical control methods leaves deployment of host resistance to be the only option to manage this disease. However, current commercial varieties are mainly susceptible to BLS. Therefore, our goal was to identify sources of resistance from diverse barley germplasms and map associated genetic factors. To do so, we evaluated a subset of the World Barley Core Collection (BCC), consisting of 198 accessions, on their reaction to BLS from 2013 to 2016 under natural or artificially inoculated disease pressures. Ten accessions exhibited consistently low disease severities over 4 years of evaluations. Using genotype data from the T3/Barley database, genome-wide association studies were conducted to identify marker-trait associations (MTAs) in this barley mini-core panel for BLS resistance. Utilizing four mixed-model analyses (mixed linear model, multi-locus mixed model, fixed and random model circulating probability unification, and Bayesian-information and linkage-disequilibrium iteratively nested keyway [BLINK]), nine significant MTAs were detected using the primary model, BLINK, including one in chromosome 1H, six in chromosome 2H, and one each in chromosomes 3H and 5H. Associations in chromosomes 2H and 3H appear to be in the same region with loci identified in a previous association study, reinforcing their potential relevance. The identified resistant barley accessions and associated markers will be valuable in breeding BLS-resistant barley varieties.