Reduction of mycotoxigenic Aspergillus flavus infection and aflatoxin contamination in maize treated with the biological product AF-X1: second year of field trials

Aflatoxin contamination of maize, used for both human and animal consumption, is a serious constraint for final users health. Biocontrol is one of the measures that proved to be effective in aflatoxin reduction. This strategy is based on the application of non toxigenic Aspergillus flavus strains in maize fields to displace aflatoxin-producers during crop development. Field trials, for the second year running, in two different Tuscany locations using maize hybrids of maturity class FAO 400 and 600 were conducted. Georeferenced plots (1 ha) were treated or not treated with the biological product AF-X1 (25 kg ha-1) and kerne samples from plants at five sites on the two diagonals of each plot were collected. 100 maize kernels from each plot were surface sterilized and plated on PDA amended with streptomycin. Seeds mycoflora was assessed and all the Aspergillus spp. colonies were transferred on AFPA, CZ, CAM and YES media in order to determine toxigenic and non toxigenic A. flavus isolates. Moreover, maize flour samples were analyzed for aflatoxins by HPLC-FLD. The percentage range of non toxigenic A. flavus was higher in treated plots compared to untreated plots (31.5-91.3% vs 1.7-41%) and the average ratio of non toxigenic/toxigenic isolates was 79 and 6 in seeds from treated and non treated plots, respectively. The overall average aflatoxin B1 concentration in maize from treated plots was 1.8 μg kg-1 and in untreated plots was 9.5 μg kg-1. The percent reduction in aflatoxin B1 concentration ranged from 67.7% to 99.7%.