Occurrence and Identification of Aspergillus Section Flavi in the Context of the Emergence of Aflatoxins in French Maize.

Sylviane Bailly,Jean-Denis Bailly,Anwar Mahgubi,Olivier Puel,Isabelle Oswald,Amaranta Carvajal-Campos,Sophie Lorber,Béatrice Orlando

doi:10.3390/toxins10120525

Abstract

Aflatoxins (AFs) are secondary metabolites produced by Aspergillus section Flavi during their development, particularly in maize. It is widely accepted that AFB1 is a major contaminant in regions where hot climate conditions favor the development of aflatoxigenic species. Global warming could lead to the appearance of AFs in maize produced in Europe. This was the case in 2015, in France, when the exceptionally hot and dry climatic conditions were favorable for AF production. Our survey revealed AF contamination of 6% (n = 114) of maize field samples and of 15% (n = 81) of maize silo samples analyzed. To understand the origin of the contamination, we characterized the mycoflora in contaminated samples and in samples produced in the same geographic and climatic conditions but with no AFs. A special focus was placed on Aspergillus section Flavi. A total of 67 strains of Aspergillus section Flavi were isolated from the samples. As expected, the strains were observed in all AF+ samples and, remarkably, also in almost 40% of AF− samples, demonstrating the presence of these potent toxin producers in fields in France. A. flavus was the most frequent species of the section Flavi (69% of the strains). But surprisingly, A. parasiticus was also a frequent contaminant (28% of the strains), mostly isolated from AF+ samples. This finding is in agreement with the presence of AFG in most of those samples.

Highlights

Aflatoxins (AFs), and Aflatoxin B1 (AFB1), are the most dangerous mycotoxins identified to date
Our results demonstrate that Aspergillus section Flavi is frequently present in maize exposed to heat and drought and that, in the case of favorable environmental conditions, its development can lead to AF contamination
In most of the country, these high temperatures were accompanied by a rainfall deficit of more than 40% compared to the average, which dried out the top soil layer and caused heat stress in maize [40], especially during the flowering and silk tanning periods

Summary

Introduction

Aflatoxins (AFs), and Aflatoxin B1 (AFB1), are the most dangerous mycotoxins identified to date. AFB1 is the most potent natural carcinogenic compound, responsible for hepatocarcinoma in humans and classified by IARC in the group I of carcinogenic molecules for both humans and animals [1,2]. This toxin is immunosuppressive and has been associated with growth impairment in children [3,4]. AFs are secondary metabolites produced by Aspergillus section Flavi.

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