Genome-Wide Association Mapping Reveals Genetic Architecture of DurAble Spot Blotch Resistance in US Barley Breeding Germplasm

摘要

Spot blotch, an economically important disease of both barley and wheat, is caused by Cochliobolus sativus (anamorph: Bipolarissorokiniana). The disease has been reported in many regions of world, but is particularly severe on barley in the Upper Midwest region of the United States, adjacent areas of Canada and northeastern Australia. Durable resistance has been attained in Midwest six-rowed malting cultivars for over 50 years and is derived from line NDB112. To identify loci conferring resistance to spot blotch, an association mapping approach was conducted in US breeding germplasm (3,840 lines) genotyped with 3,072 Single Nucleotide Polymorphism (SNP) markers. Three Quantitative Trait Loci (QTL) Rcs-qtl-1H-11_10764, Rcs-qtl-3H-11_10565 and Rcs-qtl-7H-11_20162 conferring both seedling and adult resistance were identified. Each individual QTL only partially reduced the Infection Response (IR) (from 0% to 20%) at the seedling stage and severity (from 20% to 29%) at the adult plant stage. However, all three QTL together reduced the seedling IR and adult plant severity by 47% and 83%, respectively, and comprise the Midwest Six-Rowed Durable Resistance Haplotype (MSDRH). The identified MSDRH will be valuable for marker-assisted selection of spot blotch resistance in breeding programs.