Inhibition of aflatoxin formation in aspergillus species by peanut (Arachis hypogaea) seed stilbenoids in the course of peanut-fungus interaction

Authors: Sobolev, Victor; Walk, Travis; Arias De Ares, Renee; Massa, Alicia; Lamb, Marshall

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2019
Publication Date: 5/17/2019
Citation: Sobolev, V., Walk, T., Arias De Ares, R.S., Massa, A.N., Lamb, M.C. 2019. Inhibition of aflatoxin formation in aspergillus species by peanut (Arachis hypogaea) seed stilbenoids in the course of peanut-fungus interaction. Journal of Agricultural and Food Chemistry. 67(22):6212-6221. https://doi.org/10.1021/acs.jafc.9b01969.
DOI: https://doi.org/10.1021/acs.jafc.9b01969

Interpretive Summary: Under specific weather conditions, common soil fungi, Aspergillus flavus and A. parasiticus, invade pre-harvest peanut seeds and other important crops and produce carcinogenic aflatoxins. Detection of aflatoxins and further processing of crops are mandated to ensure that contaminated agricultural products do not enter food channels. The strict legislation and associated necessary actions lead to significant economic losses worldwide. Under favorable conditions, in response to a fungal attack, peanut seeds produce antifungal chemicals, known as phytoalexins. The mechanism of such peanut-fungus interaction has not been sufficiently researched. The present research demonstrated that in the course of peanut-fungus interaction, phytoalexins can completely suppress aflatoxin formation in Aspergillus species, when concentrations of fungal spores introduced to the seeds were low. When fungal spore concentrations were high, the spores germinated and produced aflatoxins. The research provided new knowledge on peanut-fungus interaction. Such knowledge is crucial for elaboration of new strategies that prevent aflatoxin formation by Aspergillus species in peanut.

Technical Abstract: Aspergillus flavus and A. parasiticus, the common soil fungi, are opportunistic pathogens that invade peanut seeds at different stages of their development. These fungi often produce highly carcinogenic aflatoxins that possess threat to human and animal health through food chains and cause significant economic losses worldwide. Detection of aflatoxins and further processing of crops are mandated to ensure that contaminated agricultural products do not enter food channels. When the seed water activity level is sufficiently high, the fungus-challenged peanut seeds produce numerous structurally related stilbenoids capable of retarding fungal development. Our previous research demonstrated a significant reduction, or virtually complete suppression of aflatoxin production, when selected Aspergillus toxigenic species were fed with major individual peanut stilbenoids, arachidin-1, arachidin-3, and chiricanine A added to the growth medium. However, it was not clear whether fungal growth and aflatoxin inhibition by the de novo synthesized stilbenoids occurs in the course of peanut-fungus interaction. The present research revealed that stilbenoid production in wounded seeds increased with higher spore concentrations applied to the seeds. During the peanut-fungus interaction, aflatoxin formation was completely suppressed in A. flavus and A. parasitus strains tested, when lower concentrations of spores were introduced to wounded peanuts. When fungal spore concentrations were high, the spores germinated and produced aflatoxins. The research provided new knowledge on peanut-fungus interaction. Such knowledge is crucial for elaboration of new strategies that prevent aflatoxin formation by Aspergillus species in peanut.