ARS | Publication request: Resistance among U.S. wheat Triticum aestivum cultivars to the wheat pathotype of Magnaporthe oryzae

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2011
Publication Date: August 8, 2011
Citation: Cruz, C., Bockus, W., Pedley, K.F., Peterson, G.L., Stack, J., Tang, X., Valent, B. 2011. Resistance among U.S. wheat Triticum aestivum cultivars to the wheat pathotype of Magnaporthe oryzae. Phytopathology. 101:S220.

Technical Abstract: Magnaporthe oryzae is the causal agent of blast on several graminaceous plants. The M. oryzae population causing wheat blast has not been found outside South America. U.S. wheat production is at risk to this pathogen if introduced and established. Proactive testing of US wheat cultivars for their reaction to blast and identification of resistance resources is crucial, due to the national and global importance of the U.S. wheat industry. In this study, the phenotypic reaction of 72 U.S. wheat (Triticum aestivum) cultivars to M. oryzae was determined. Testing of cultivars was performed in a Biological Safety Level-3 containment laboratory; all inoculations used the T-25 isolate. Visual assessment of the percentage-killed spikelets or leaf area affected by blast was recorded. To determine if seedling and adult plant severity were correlated, 12 wheat cultivars showing different levels of reaction to blast were inoculated at the head and seedling stage. There was a significant correlation in the reaction to blast at both stages; however, a maximum of 64% of the seedling reactions was explained by the head reactions. Therefore, testing of all 72 cultivars occurred at the head stage. Among cultivars tested at least twice, a continuum in severity to head blast was observed. Cultivars Everest and Karl 92 were highly susceptible with more than 90% disease severity. Cultivar Jagalene was highly resistant with less than 1% severity, as were cultivars Postrock, Overley, Jagger, Jackpot, and Santa Fe with less than 2.5% severity.