Spring barley accessions with dual spot blotch and net blotch resistance

Spot blotch and net blotch are common foliar diseases of barley in the upper midwestern United States and are capable of causing significant reductions in both the yield and quality of the crop. Currently, there are no cultivars grown in the region that possess high levels of resistance to net blotch, and recent evidence suggests that the durable spot blotch resistance present in six-row malting types may be vulnerable to virulent isolates of Cochliobolus sativus. To identify new sources of resistance, over 5000 accessions of barley from the USDA National Small Grains Collection and Texas barley breeding program were evaluated for their reaction to spot blotch and net blotch in field nurseries established at Fargo and Langdon, North Dakota, respectively. Eighteen accessions that exhibited a true spring type habit and did not have any known midwestern US germplasm in their parentage were evaluated in additional field and greenhouse tests. All 18 accessions were confirmed to carry field resistance to both diseases, but their levels of resistance varied. Seedling tests also were conducted in the greenhouse to determine whether the selected accessions carried broader resistance against different pathotypes of each pathogen. Several accessions were susceptible to one or more of the pathogen isolates, indicating potential vulnerability of their field resistance. Of the 18 accessions evaluated in this study, 8 (CIho 2291, CIho 7021, PI 58228, PI 83794, PI 428626, PI 434771, PI 467387, and Tx 7934) exhibited the broadest resistance across different pathogen isolates as revealed in the seedling tests and may be the best sources of dual spot blotch and net blotch resistance for barley breeding programs.