Submitted to: Toxicon
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2010
Publication Date: 10/16/2010
Citation: Stipanovic, R.D., Puckhaber, L.S., Bell, A.A., Liu, J. 2010. Phytotoxicity of fusaric acid and analogues to cotton. Toxicon. 57:176-178.
Interpretive Summary: The plant pathogen Fusarium oxysporum f. sp. vasinfectum produces two chemicals that are toxic to plants. These compounds are called fusaric acid and fusaric acid methyl ester. Since these compounds occur naturally and are toxic to plants, they could be used as herbicides in organic farming. In addition, compounds with similar structures might be useful as synthetic herbicides that could be used in conventional farming. We developed an assay to test the herbicidal activity of these compounds and structurally related compounds. We found the compounds produced by Fusarium oxysporum f. sp. vasinfectum were more toxic than any of the structurally related compounds tested. Thus, this plant pathogen has developed a very effective chemical to debilitate plants, and as such, it may be useful in controlling weeds in organic farming operations.
Technical Abstract: We developed a bioassay to test the phytotoxicity of chemicals to cotton and used it to determine the relative toxicity of fusaric acid (3-butylpicolinic acid), picolinic acid, and related analogs. In contrast to previous studies, we found the carboxylic acid group is essential for phytotoxicity. Nicotinic acid was considerably less phytotoxic than picolinic acid, and conversion of picolinic acid to the amide or N-oxide decreased phytotoxicity. Increasing the alkyl chain length at the 5-position on picolinic acid from two up to five carbon atoms increased phytotoxicity. The methyl ester of fusaric acid was the most phytotoxic compound tested.