|Minyo, Richard Jr.|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2005
Publication Date: 5/1/2006
Citation: Engle, J.S., Lipps, P.E., Minyo, R.J. 2006. Reaction of commercial soft red winter wheat cultivars to stagonospora nodorum in the greenhouse and field. Plant Disease. Interpretive Summary: Stagonospora leaf and glume blotch can be an economically costly wheat disease in years with severe disease levels in Ohio. Differences in Stagonospora nodorum isolate aggressiveness have been observed between isolates obtained from different areas of North America. Resistance studies across North America rely on local populations of the pathogen, which may hinder the reproducibility of the results on the same test genotypes in different areas. This study examined twenty-seven genotypes that had previously been reported as moderately resistant to Stagonospora leaf or glume blotch for their reaction to isolates of Stagonospora nodorum obtained in Ohio. The results from both greenhouse and field studies indicated that most of the wheat genotypes previously reported as resistant from different areas of North America did have moderately resistant reactions to isolates of Stagonospora nodorum obtained from Ohio. Some of the genotypes had higher Stagonospora leaf and glume blotch resistance than the current wheat lines. These results indicate that there may be genes for resistance in these older genotypes that have not been transferred to the current breeding lines. Determining where and incorporating this resistance into current breeding lines may be possible through future studies since the results of this study indicate that the resistance genes are viable in these older genotypes.
Technical Abstract: Twenty-seven wheat genotypes previously reported in the literature as resistant to Stagonospora leaf and glume blotch were tested for their reaction to Stagonospora nodorum isolates obtained from Ohio. Four genotypes had high severities of leaf blotch in the greenhouse, ranging from 25.8% to 35.8% flag leaf area affected (FLAA), and their severities were not significantly different from each other. Nine genotypes, with leaf blotch severities ranging from 4.4% to 16.5% FLAA, had lower severities than the rest, but their severities were not significantly different from each other. The other genotypes had intermediate reactions, but the disease severity observed on some of these genotypes did not differ statistically from the more resistant or more susceptible genotypes tested. Hadden and Navarro, did not survive the winter in the field plot, while Iohardi had severe powdery mildew. The highest leaf blotch severity was observed on the susceptible check, AGRA GR863, 66.7% FLAA. There was no statistical difference among 20 of the genotypes tested and the lowest observed disease severity of 3.0 FLAA. AGRA GR863 had the highest glume blotch severity, 51.0%, observed in the field plots. There was no statistically significant difference among the 18 genotypes with less than 25% glume area affected in the field. These results indicate that the tested genotypes may have potential sources of Stagonospora leaf and glume blotch resistance that could be incorporated into germplasm with current desirable traits.