Effect of atrazine on growth and production of AFB 1 in Aspergillus section Flavi strains isolated from maize soils.

Atrazine is one of the most frequently used herbicides in Argentina for controlling broadleaf weeds and annual grasses. Currently, there is limited information on the impact of triazine herbicides on mycotoxin production and growth parameters of toxigenic fungi in maize. The objective of this study was to evaluate the effect of different concentrations of atrazine on the lag phase prior to growth, the growth rate, and on production of aflatoxin B1 (AFB1 ) of Aspergillus flavus and Aspergillus parasiticus strains, on maize meal extract agar (MMEA) under different water activities (aW ) and temperatures. A commercial formulation of atrazine was added to MMEA medium at 0, 5, 10, 50, or 100 mmol/l, adjusted to 0.98, 0.95, and 0.93 aW , and incubated at 28 °C and 37 °C for 21 days. AFB1 was determined by HPLC after 7, 14, and 21 days of incubation. In the control treatments, a significant increase in the time prior to growth was observed and as the aW decreased, at both temperatures, the growth rate of the strains also decreased. A significant increase in growth rate was observed as the concentration of atrazine in the medium increased, for all aW levels tested. The optimal conditions for the accumulation of AFB1 in the control treatments were 0.98 aW and 28 °C, after 7 days of incubation. As the concentration of herbicide increased, AFB1 production also increased (P < 0.05). These results add to the knowledge about consequences with regard to aflatoxin production of the use of excessive atrazine doses in extensive maize culture.