Evaluation of biocontrol agent for the reduction of aflatoxin in peanuts in Argentina

BARROS, G.

Mendoza

Conferencia; . ISM 2011 Conference; 2011

Peanut (Arachis hypogaea L.) is an economically important crop in Argentina since our country ranks second as peanut exporter in the world. Most of the production is localised in the centre of Córdoba Province. Aflatoxin contamination of peanuts results from growth in peanut kernels by toxigenic strains of Aspergillus section Flavi. Contaminated lots of peanuts cannot be used for human consumption and therefore represent great economic losses for the peanut industry. One strategy that has been developed for reducing preharvest aflatoxin contamination of crops is biological control, which is achieved by applying competitive non-toxigenic strains to the soil of developing crops. Aspergillus species from section Flavi have been isolated from soil and peanuts cultivated in the main peanut production area in Argentina and characterized in relation to species distribution, toxigenic profile and genetic diversity. These studies allowed us to select strains with potential use as antagonists of toxigenic strains in biocontrol assays. We have conducted several studies of four harvest season (2008 to 2011) with the aim to evaluate an atoxigenic A. flavus strain (AFCHG2) naturally occurring in soil from Córdoba Province, as a potential biocontrol agent to reduce aflatoxin production in peanuts under field and storage conditions. Since atoxigenic A. flavus AFCHG2 colonies cannot be differentiated from wild-type strains, the evolution of the biocontrol agent during the studies was followed using the shift of the atoxigenic/toxigenic ratio in the treated in relation to control plots. The atoxigenic A. flavus strain was characterized previously as belong to vegetative compatibility group (VCG) infrequent in soil on Cordoba Province. In this way, the VCGs analysis was used to monitor the evolution of this strain among the soil A. flavus population recovered on maturation pod stage. The studies demonstrated that the atoxigenic strain applied remained on the soil, competed with mycoflora resident and was the dominant strain at pods ripening. The effectiveness of the atoxigenic strain applied at preharvest stage was demonstrated under conducive conditions for aflatoxin production by achieved coverage of the crop during pods ripening. Relative levels of aflatoxin B1 reduction ranged from 64% to 75%. This is the first study done using the exclusion competitive strategy to reduce the risk of aflatoxin contamination in peanuts done in Argentina using a biopesticide based on native A. flavus strain.