Implantation of Aspergillus Section Flavi in French Maize and Consequences on Aflatoxin Contamination of Maize at Harvest: Three-Year Survey

The worldwide distribution of aflatoxin B1, a carcinogenic mycotoxin, is changing due to climate change. This frequent contaminant of crops in tropical and subtropical regions is an emerging threat in Europe. Its first appearance in French maize was reported in 2015, a year with exceptional climatic conditions. But, from this year, such conditions (drought during spring and hot summers) occurred regularly, raising the question of a possible durable implantation of aflatoxigenic fungal species in French maize fields. To answer this question, 554 maize samples were collected during three consecutive years (2018-2020) throughout the French territory. They were subjected to mycological analysis and strains belonging to the <i>Flavi</i> section of the <i>Aspergillus</i> genus were identified, and their toxigenic potential was determined. This survey demonstrates that <i>Aspergillus</i> section <i>Flavi</i> are now frequent contaminants of maize since they were observed in more than 50% of samples in 2018 and 2019. This prevalence sharply increased in 2020 to reach 80% contamination. In parallel, the frequency of contamination with aflatoxins also increased. While it was very limited during the first two years of the study, despite favorable climatic conditions, contamination with aflatoxins was present in 16% of samples analyzed in 2020, exceeding E.U. regulation by 5%. Even if <i>Aspergillus flavus</i> is the dominant species, representing more than 90% of isolated strains, <i>Aspergillus parasiticus</i> seems to play a major role in grain contamination, as demonstrated by the presence of AFG in 50% of contaminated samples. These findings highlight the need to rethink the monitoring and management of aflatoxin risk in France for the future.