Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2012
Publication Date: 2/29/2012
Citation: Dzhavakhiya, V., Shcherbakova, L., Semina, J., Zhemchuzhina, N., Campbell, B.C. 2012. Chemosensitization of plant pathogenic fungi to agricultural fungicides. Frontiers in Microbiology. 3:87. Interpretive Summary: Scientists in the Plant Mycotoxin Research Unit at the Western Regional Research Center have developed a cooperative research project with Russian scientists at the All Russian Research Institute of Phytopathology, Moscow. The project looks to developing methods to improve the control of fungal pathogens of crops. The scientists have discovered a way of improving the effectiveness of commercial fungicides by weakening fungal pathogens with safe, natural products, making them more vulnerable to fungicides. This process of increasing the sensitivity of the pathogens to fungicides is called chemosensitization. In this report, a number of safe compounds are identified that increase the sensitivity of a number of fungal pathogens, affecting Russian crops, to fungicides that are widely used in Russia. In one case, unknown compounds produced by a safe fungus are identified that also have this chemosensitizing activity. This project represents a good example of scientific collaboration in agriculture between Russian and American scientists. The discovery of chemosensitizing compounds could help control fungal pathogens with less expense and resulting in less of a threat to the environment.
Technical Abstract: Continual use of fungicides in agriculture often results in development of resistance in pathogens. A new strategy to aid in overcoming or minimizing this problem is enhancement of pathogen sensitivity to fungicides by chemosensitization. This involves combining fungicides with certain non-fungicidal substances or antifungal compounds at non-fungicidal concentrations. Activity of azole and strobilurin fungicides were increased through co-application with certain natural or synthetic products against several economically important plant pathogenic fungi. Quadris (azoxystrobin) combined with thymol at a non-fungitoxic concentration produced almost three times higher growth inhibition of Bipolaris sorokiniana than the fungicide, alone. The effect of Dividend (difenoconazole) applied with thymol significantly enhanced antifungal activity against B. sorokiniana and Stagonospora nodorum. Folicur combined with 4-hydroxybenzaldehyde (4-HBA), 2,3-dihydroxybenzaldehyde (2,3-DHBA) or thymol synergistically inhibited growth of this Alternaria alternata. Co-application of Folicur and 4-HBA also resulted in enhancement of antifungal activity against Fusarium culmorum. Lastly, extracellular metabolites in the culture liquid of F. sambucinum biocontrol isolate FS-94 had chemosensitizing activity, increasing S. nodorum sensitivity to Folicur and Dividend. Such chemosensitization decreases the probability of pathogen resistance, reduces the toxic impact on the environment by lowering effective dosage levels, and improves efficacy of antifungal agents.