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United States Department of Agriculture

Agricultural Research Service

Title: Effects of Methyl Jasmonate on Phytoalexin Production and Aflatoxin Controlin the Developing Cotton Boll

Author
item Zeringue Jr, Hampden

Submitted to: Biochemical Systematics and Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 14, 2000
Publication Date: N/A

Interpretive Summary: Aflatoxins are highly toxic compounds produced by the molds Aspergillus flavus and Aspergillus parasiticus. Infection of important food/feed crops with toxigenic Aspergillus mold with subsequent aflatoxin contamination reduces both the quality and economic value of the crop and is a potential health problem to both man and animal. One aspect of our research is the investigation of natural products to control aflatoxin contamination. It was found that when developing cotton bolls were inoculated with a mold extract and then exposed to the natural plant hormone, methyl jasmonate, that a 2- to 3-fold increase in protective chemical compounds called phytoalexins were produced by the cotton plant. In a separate experiment, it was found that a 95% inhibition of aflatoxin contamination resulted in the cottonseeds of mature bolls that had been pretreated with the above natural compounds prior to inoculation with a toxigenic strain of Aspergillus. Apparently the induced phytoalexins were responsible for the aflatoxin control that resulted. This information would be beneficial to plant breeders and molecular biologists who are searching for disease and aflatoxin resistant traits to decrease the incident of aflatoxin contamination in important food/feed crops.

Technical Abstract: Artificially wounded 22 to 27-day old developing cotton bolls were initially inoculated with, (1) a cell-free, hotwater-soluble mycelial extract (CFME) of an atoxigenic strain of Aspergillus flavus or with, (2) chitosan lactate (CHL) or with, (3) CFME or CHL and then exposed to gaseous methyl jasmonate (MJ) or, (4) exposed to MJ alone. Five days after rthese treatments, the induction of the sesquiterpenoid naphthol phytoalexins, 2,7-dihydroxycadalene and 2-hydroxy-7-methoxy cadalene, lacinilene C, lacinilene C7-methyl ether, and the coumarin phytoalexin-scopoletin were determined on the excised carpel discs surrounding the inoculated surfaces of the developing cotton bolls. The results indicated a 2- or 3-fold increase in the production of the phytoalexins when gaseous methyl jasmonate was added in combination to the CFME or the CHL elicitors. In a separate experiment, 22-27 day old developing cotton bolls were pretreated for a 5-day period as described above and then a spore suspension of a toxigenic strain of A. flavus was introduced into a second artificial wound which was produced adjacent to the first wound. At boll maturity, the cottonseeds located within the locules underlying the areas that were pre-treated with both elicitors and MJ then later infected with toxigenic A flavus exhibited a 75% to 95% aflatoxin B1 inhibition. These results suggest a possible host defense mechanism which may be triggered by both elicitor and MJ.

Last Modified: 9/10/2014
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