|Crutcher, Frankie - Montana State University|
|Bell, Alois - Al|
|Stipanovic, Robert - Bob|
|Nichols, Robert - Cotton, Inc|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2017
Publication Date: 5/24/2017
Citation: Crutcher, F., Puckhaber, L.S., Bell, A.A., Liu, J., Duke, S.E., Stipanovic, R.D., Nichols, R. 2017. Detoxification of fusaric acid by the soil microbe Mucor rouxii. Journal of Agricultural and Food Chemistry. 65(24):4989-4992.
Interpretive Summary: A highly pathogenic strain of cotton wilt pathogen Fusarium oxysporum f. sp. vasinfectum has been identified in California. This strain, unlike the traditional less pathogenic strains previously found in the U.S., causes severe disease even in the absence of nematode, and thus poses a wider threat to cotton production as more than 50% of cotton in the U.S. is grown on heavy alkaline soils. This strain produces very high levels of fusaric acid that is highly toxic to cotton plants and helps the pathogen to compete with other microbes in the soil. Finding a mechanism to detoxify fusaric acid may provide a tool to control this new pathogen. We screened soil and lab strains of microbes and identified a stain of Mucor rouxii which was highly resistant to fusaric acid and efficiently converted it to 8-hydroxyfusacic acid. Tests on cotton indicated that the conversion product is significantly less toxic than fusaric acid. Genes responsible for this conversion may be used to enhance fusaric acid resistance of biocontrol agents to effectively manage this new strain of pathogen.
Technical Abstract: An unusually aggressive biotype of the root rotting pathogen of cotton, Fusarium oxysporum f. sp. vasinfectum (Fov), has been identified in the Western Hemisphere in some cotton fields in California. This pathogen produces copious quantities of the plant toxin fusaric acid (5-butyl-2-pyridinecarboxyylic acid) compared to isolates of Fov indigenous to the US. Fusaric acid is a general toxin that debilitates the plant and helps the pathogen survive in the soil. We have identified a laboratory strain of Mucor rouxii that converts fusaric acid into 8-hydroxyfusaric acid. The latter compound is significantly less phytotoxic to cotton as determined in a leaf bioassay. Based on this and other bioassays of hydroxylated butyl-2-pyridinecarboxylic acids, it appears that these fusaric acid metabolites effect a general detoxification. Genes that cause this conversion may be useful in developing biocontrol agents to manage this pathogen.