AFLATOXIN MINIMIZATION PROGRAMME IN ROMANIA BY SELECTION AND USE OF ATOXIGENIC ASPERGILLUS FLAVUS AS BIOCONTROL AGENT IN MAIZE FIELD

Recently, Aspergillus flavus arise as an emerging problem for maize in Southern Europe. After the first European aflatoxins outbreak in 2003, followed by severe contamination in 2012 and 2015, the prevention of aflatoxins in maize field became a relevant issue. Competitive exclusion of toxigenic Aspergillus flavus by atoxigenic strains is worldwide accepted as one of the most effective action to minimize aflatoxins risk. USA, Africa and Italy have developed some commercial biocontrol agent products and Eastern Europe countries start working in the same direction. This study aimed to select an A. flavus biocontrol agents in Romania. Therefore, Aspergillus section Flavi strains were isolated, identified and characterized, from 139 maize flour samples, representative of the whole Romanian maize growing areas. Deletions of the aflatoxins gene cluster were investigated by multiplex PCR analyses. Microsatellite alleles were bioinformatically analysed to depict the population structure. 169 strains were confirmed as A. flavus; 71 strains seems to lack at least one gene of the aflatoxins cluster. Competition tests, involved 7 chemically confirmed atoxigenic strains with huge deletions in aflatoxins cluster. Microsatellites analysis identify two main group by bayesian clustering, genetic distance-based analysis and population assignment. Strain 36.3 was selected as potential biocontrol agent, among the 7 atoxigenic strains that exhibited high aflatoxins reduction (80-96%) during in vitro competition tests. Thermally treated sorghum coated with the inoculum of this atoxigenic strain was distributed in maize field trials (approximately 1 ha) in Romania (2018 and 2019). Since, very low aflatoxins contamination was measured, even in untreated fields, during both years, the biocontrol efficacy needs to be confirmed by further field data.