Cumulative Effects of Non-Aflatoxigenic Aspergillus flavus Volatile Organic Compounds to Abate Toxin Production by Mycotoxigenic Aspergilli

Abstract

Previously, authors reported that individual volatile organic compounds (VOCs) emitted by non-aflatoxigenic Aspergillus flavus could act as a mechanism of biocontrol to significantly reduce aflatoxins and cyclopiazonic acid (CPA) produced by toxigenic strains. In this study, various combinations and volumes of three mycotoxin-reductive VOCs (2,3-dihydrofuran, 3-octanone and decane) were assessed for their cumulative impacts on four Aspergillus strains (LA1-LA4), which were then analyzed for changes in growth, as well as the production of mycotoxins, including aflatoxins, CPA and multiple indole diterpenes. Fungal growth remained minimally inhibited when exposed to various combinations of VOCs. No single combination was able to consistently, or completely, inhibit aflatoxin or CPA across all toxigenic strains tested. However, the combination of 2,3-dihydrofuran and 3-octanone offered the greatest overall reductions in aflatoxin and CPA production. Despite no elimination of their production, findings showed that combining VOCs produced solely by non-aflatoxigenic A. flavus still inhibited several agriculturally important mycotoxins, including B and G aflatoxins and CPA. Therefore, other VOC combinations are worth testing as post-harvest biocontrol treatments to ensure the prolonged effectiveness of pre-harvest biocontrol efforts.

Variation with In Vitro Analysis of Volatile Profiles among Aspergillus flavus Strains from Louisiana

“…The four Aspergillus strains utilized for this study (LA1-LA4) have been described previously [18,21,22]. Briefly, LA1 is a non-aflatoxigenic and CPA-negative A. flavus strain, exhibiting a mixed morphotype of abundant large (L) and small (S) sclerotia and conidia.…”

“…LA2 is a highly toxigenic A. flavus strain that exhibits a non-sclerotial morphotype and produces abundant conidia. On yeast extract sucrose (YES) medium, LA2 to produces B aflatoxins at concentrations of around 21,000 ppb and CPA around 1200 ppm [22]. LA3 is also a highly toxigenic A. flavus strain (~54,000 ppb for B aflatoxins and ~16,000 ppm for CPA on YES) that exhibits an abundance of S (small) sclerotia and limited production of conidia.…”

“…Spore suspensions were made for each isolate by growing them on PDA and collecting conidia from 7 d old cultures. Spores were suspended in 1 mL of 0.001% Triton X detergent at a concentration of 1 × 10 6 spores/mL as used in previous studies involving these strains [18,22,23].…”

“…Uncharacterized extrolites [23] and VOCs (unpublished data) from LA1 have been shown to reduce aflatoxin and CPA levels in vitro. However, LA1 would not make a good biocontrol strain because it produces the tremorgenic mycotoxin aflatrem in concentrations of the tens-of-thousands ppb [22]. Feeding studies have shown that aflatrem causes neurological deterioration in mice [42,43], so it would not be safe for consumers to ingest high quantities of aflatrem, even though the aflatoxin levels are greatly reduced.…”

Microbiota of maize kernels as influenced by Aspergillus flavus infection in susceptible and resistant inbreds

“…The wild-type toxigenic strain, Tox4 (SRRC 573; 07-C-1-1-1; LA2) was first isolated in Louisiana (Sweany et al, 2011) and considered to be appropriate for our studies since it is locally adapted. It produces both aflatoxin and cyclopiazonic acid (CPA) at concentrations up to the tens-ofthousands ppb (Moore et al, 2019(Moore et al, , 2021(Moore et al, , 2022. It was transformed with mCherry RFP to generate transgenic strain SRRC 573-R and distinguish it among amplicons derived from other prevailing A. flavus strains in our experimental plots.…”