Sallam Ahmad H, Tyagi Priyanka, Brown-Guedira Gina, Muehlbauer Gary J, Hulse Alex, Steffenson Brian J
Department of Plant Pathology, University of Minnesota, St. Paul, Minnesota 55108.
Department of Crop and Soil Sciences, North Carolina State University, Raleigh, North Carolina 27695.
G3 (Bethesda). 2017 Oct 5;7(10):3491-3507. doi: 10.1534/g3.117.300222.
Stem rust was one of the most devastating diseases of barley in North America. Through the deployment of cultivars with the resistance gene , losses to stem rust have been minimal over the past 70 yr. However, there exist both domestic (QCCJB) and foreign (TTKSK aka isolate Ug99) pathotypes with virulence for this important gene. To identify new sources of stem rust resistance for barley, we evaluated the Wild Barley Diversity Collection (WBDC) (314 ecogeographically diverse accessions of subsp. ) for seedling resistance to four pathotypes (TTKSK, QCCJB, MCCFC, and HKHJC) of the wheat stem rust pathogen ( f. sp. , ) and one isolate (92-MN-90) of the rye stem rust pathogen ( f. sp. , ). Based on a coefficient of infection, the frequency of resistance in the WBDC was low ranging from 0.6% with HKHJC to 19.4% with 92-MN-90. None of the accessions was resistant to all five cultures of A genome-wide association study (GWAS) was conducted to map stem rust resistance loci using 50,842 single-nucleotide polymorphic markers generated by genotype-by-sequencing and ordered using the new barley reference genome assembly. After proper accounting for genetic relatedness and structure among accessions, 45 quantitative trait loci were identified for resistance to across all seven barley chromosomes. Three novel loci associated with resistance to TTKSK, QCCJB, MCCFC, and 92-MN-90 were identified on chromosomes 5H and 7H, and two novel loci associated with resistance to HKHJC were identified on chromosomes 1H and 3H. These novel alleles will enhance the diversity of resistance available for cultivated barley.
秆锈病曾是北美大麦最具毁灭性的病害之一。通过部署携带抗性基因的品种，在过去70年里，秆锈病造成的损失已降至最低。然而，存在对这一重要基因具有毒性的国内（QCCJB）和国外（TTKSK，即分离株Ug99）致病型。为了鉴定大麦秆锈病抗性的新来源，我们评估了野生大麦多样性收集群体（WBDC）（314份来自不同生态地理区域的 亚种材料）对小麦秆锈病病原菌（禾柄锈菌小麦专化型， ）的4种致病型（TTKSK、QCCJB、MCCFC和HKHJC）以及黑麦秆锈病病原菌（禾柄锈菌黑麦专化型， ）的一个分离株（92-MN-90）的苗期抗性。基于感染系数，WBDC中的抗性频率较低，从对HKHJC的0.6%到对92-MN-90的19.4%不等。没有一份材料对所有5种病原菌都具有抗性。利用通过简化基因组测序产生并根据新的大麦参考基因组组装排序的50,842个单核苷酸多态性标记，进行了全基因组关联研究（GWAS）以定位秆锈病抗性位点。在适当考虑材料间的遗传相关性和结构后，在所有7条大麦染色体上共鉴定出45个抗 秆锈病的数量性状位点。在5H和7H染色体上鉴定出3个与抗TTKSK、QCCJB、MCCFC和92-MN-90相关的新位点，在1H和3H染色体上鉴定出2个与抗HKHJC相关的新位点。这些新的等位基因将增加栽培大麦可用的抗性多样性。
