Impact of pre-harvest elicitors on the toxigenic mycobiota and mycotoxin risk in dried figs: A holistic safety assessment.

Abstract

Pre-harvest fungal contamination of figs (Ficus carica L.) poses a significant food safety risk due to mycotoxin production. While chemical elicitors are proposed as a sustainable control strategy, their impact on the autochthonous mycobiota and mycotoxin profiles during fig maturation and sun-drying is largely unknown. This study evaluated the effects of pre-harvest applications of γ-aminobutyric acid (GABA), oxalic acid (OA), and melatonin (MT) on the fungal community dynamics and 16 mycotoxins across five ripening and senescence stages of 'Calabacita' figs. Results showed a clear ecological succession from field fungi (Cladosporium spp.) in unripe figs to xerotolerant storage fungi (Aspergillus spp.) in dried figs. MT treatments demonstrated a protective effect, significantly reducing final moisture content to below the 26% safety threshold and limiting the prevalence of toxigenic species. In contrast, the 10 mM GABA treatment, despite reducing overall mould counts in some stages, selectively fostered a high-risk consortium of toxigenic fungi (A. niger, Aspergillus section Flavi) and their mycotoxins, leading to co-contamination with aflatoxins (AFB1, AFB2, AFG1), cyclopiazonic acid (CPA), and O-methyl-sterigmatocystin (OM-STG). While MT shows promise as a pre-harvest strategy to enhance the microbiological safety of dried figs, the 10 mM GABA treatment proved detrimental. These findings highlight the critical need for a holistic risk assessment of elicitors, considering their unintended and sometimes paradoxical effects on the native mycobiota and the resulting mycotoxin risk.