Artificial Inoculation of Wheat for Selecting Resistance to Stagonospora Nodorum Blotch

Authors: Cowger, Christina; MURPHY, PAUL - NORTH CAROLINA STATE UNIV

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2006
Publication Date: 2/1/2007
Citation: Cowger, C., Murphy, P. 2007. Artificial Inoculation of Wheat for Selecting Resistance to Stagonospora Nodorum Blotch. Plant Disease. 91:539-545.

Interpretive Summary: In the eastern United States, natural epidemics of Stagonospora nodorum blotch (SNB) are not consistently severe enough to facilitate substantial progress in breeding moderately resistant cultivars of soft red winter wheat. We compared three artificial inoculation methods to natural inoculum in a field experiment involving seven wheat cultivars with varying levels of SNB resistance. Artificial inoculation methods were S. nodorum spores applied in the early winter or late spring and S. nodorum-infected wheat straw applied in early winter. The experiment was conducted at Kinston and Plymouth, NC, in 2003-04, 2004-05, and 2005-06, and all treatments had three replicates. Percent diseased canopy was assessed and comparisons were made using disease severity at a single date (early to soft dough stage) and area under the disease progress curve (AUDPC). The relative resistance level of genotypes was consistent across sites, years, and inoculum methods, although the rankings of moderately susceptible and susceptible genotypes were sometimes switched. On average, late spores and straw caused significantly more disease than early spores, which caused more disease than natural inoculum (P ' 0.05). All artificial methods had a higher mean capacity to discriminate among genotypes than did natural inoculum (P ' 0.05). Across inoculation methods and genotypes, mean yield and test weight were negatively correlated with disease severity in some, but not all, site-years. On average, artificial inoculation increased the capacity of environments to separate wheat genotypes by SNB resistance.

Technical Abstract: In the eastern United States, natural epidemics of Stagonospora nodorum blotch (SNB) are not consistently severe enough to facilitate substantial progress in breeding moderately resistant cultivars of soft red winter wheat. We compared three artificial inoculation methods to natural inoculum in a field experiment involving seven wheat cultivars with varying levels of SNB resistance. Artificial inoculation methods were S. nodorum spores applied in the early winter or late spring and S. nodorum-infected wheat straw applied in early winter. The experiment was conducted at Kinston and Plymouth, NC, in 2003-04, 2004-05, and 2005-06, and all treatments had three replicates. Percent diseased canopy was assessed and comparisons were made using disease severity at a single date (early to soft dough stage) and area under the disease progress curve (AUDPC). The relative resistance level of genotypes was consistent across sites, years, and inoculum methods, although the rankings of moderately susceptible and susceptible genotypes were sometimes switched. On average, late spores and straw caused significantly more disease than early spores, which caused more disease than natural inoculum (P ' 0.05). All artificial methods had a higher mean capacity to discriminate among genotypes than did natural inoculum (P ' 0.05). Across inoculation methods and genotypes, mean yield and test weight were negatively correlated with disease severity in some, but not all, site-years. On average, artificial inoculation increased the capacity of environments to separate wheat genotypes by SNB resistance.