In the vapors: volatilized metabolites from non-aflatoxigenic Aspergillus flavus inhibit aflatoxigenic aspergilli as potential biofumigants

Introduction Aflatoxin and other toxic fungal metabolites continue to be an issue in global agriculture. Although effective pre-harvest strategies exist and are in active use, their effectiveness can wane during storage. Therefore, processors seek viable post-harvest strategies that protect commodities from aflatoxin contamination. Recent discoveries from this lab suggest the potential for metabolite production to be a mechanism contributing to the efficacy of A. flavus biocontrol strains, whereby their secretion of soluble or volatile metabolites reduce growth and/or mycotoxin production in aflatoxigenic strains from Louisiana. Volatile metabolites from effective biocontrol strains hold potential for use as biofumigants in storage and/or transport; however, their broad-spectrum applicability must first be assessed. Methods In this study, we exposed twelve Aspergillus strains (nine of which were aflatoxigenic) originally sampled from regions outside of Louisiana to same four volatile organic compounds (VOCs) that were inhibitory to the Louisiana strains. The goal here was to see if these compounds would exhibit consistent control over aflatoxin producing strains no matter where they originated. Results Like observed for the Louisiana strains, trans -2-methyl-2-butenal more noticeably reduced growth of all strains than the other three VOCs (2,3-dihydrofuran, 3-octanone, decane). However, there were notable differences in how some strains responded to each VOC treatment regarding aflatoxin production. Strain responses to VOC treatment were variable, at times dependent on the strain, the compound, or the volume/concentration used for treatment. Discussion Although, our findings supported previous findings that VOC-mediated inhibition of aflatoxin producing fungi is possible and confirmed there are multiple compounds with great potential to exploit as biofumigants, it was determined that no compound tested thus far offers blanket control and that the most effective VOC used for biofumigation may be region dependent.