|Zeringue Jr, Hampden|
Submitted to: Toxicon
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/1999
Publication Date: N/A
Interpretive Summary: Aflatoxins are chemicals that are produced by the fungi Aspergillus flavus and Aspergillus parasiticus. These fungi commonly infect corn, cotton and peanuts, and aflatoxin produced in the crops is known to cause cancer in humans and other animals when the contaminated food or feed is ingested. Therefore, aflatoxin contaminated crops have to be disposed of and this results in very large economic losses to the corn, cotton and peanut industries. Production of certain chemicals by both cotton and corn plants, called volatile terpenes and alcohols, have been shown to be correlated with resistance in corn to A. parasiticus. The four volatile chemicals investigated in the present study were isolated from cotton. Two of the four volatile chemicals were shown to reduce growth of A. flavus and may be useful "resistance markers" in future breeding of crops for resistance to this fungus. This would lead to a reduction in aflatoxin contamination in crops and thus reduce resultant economic losses incurred by the cottonseed, corn and peanut industries.
Technical Abstract: The fungi Aspergillus flavus and Aspergillus parasiticus produce the hepatocarcinogenic, secondary metabolites, aflatoxins, prior to harvest in cottonseed, corn, peanuts and treenuts. Results have shown that aflatoxigenic strains of A. flavus or A. parasiticus grown in the presence of specific cotton-leaf volatiles exhibit alterations in aflatoxin production accompanied by variations in growth and morphology of the fungi. In this study, we examined the mechanism by which these changes occur. Four volatile compounds, two alcohols (3-methyl-1-butanol and nonanol) and two terpenes (camphene and limonene) were chosen as representative cotton-leaf volatiles based on the significant yet varied effects these volatiles had on fungal growth and/or aflatoxin production in previous investigations. The effects of volatile exposure on colony and conidial morphology were examined in correlation with fungal growth and aflatoxin production. 3-MB-treated samples exhibited a decrease in radial growth directly proportional to the volatile dosage. Additionally, 3-MB treatment resulted in loss of pigmentation accompanied by marked decrease in sporulation. Limonene and camphene-treated samples yielded negligible differences in radial growth and morphology when compared to unexposed controls. Samples grown in the presence of all doses of nonanol demonstrated uniquely aerial hyphae and radial growth was inhibited almost 50% in the presence of 100 ul of nonanol. Aflatoxin production in liquid cultures exposed to 3-MB increased, while levels in cultures exposed to all other volatiles decreased.