Influence of a glyphosate-based herbicide on growth parameters and aflatoxin B₁ production by Aspergillus section...

Glyphosate-based herbicides (GBH) are the main pesticides applied worldwide on maize production. Glyphosate-resistant weeds led to the repeated application of high doses of the pesticide. In addition to environmental conditions, the presence of GBH affects the development of Aspergillus species and aflatoxin B₁ (AFB₁) production under in vitro conditions. The aim of this work was to evaluate the influence of a commercial GBH on growth and AFB₁ production by Aspergillus flavus and Aspergillus parasiticus strains under different water activity (a_W) conditions. The following concentrations of active ingredient glyphosate were evaluated: 20, 50, 200 and 500mM. The lag phase prior to growth and growth rate did not change at 20 and 50mM (that is, at field recommended doses) at 0.98 and 0.95 a_W; however, at increasing GBH concentrations, between 200 and 500mM, the growth rate decreased at all a_W conditions. In general, as the GBH concentration increased, AFB₁ production decreased. However, a significant increase in toxin accumulation was found only at one of the a_W conditions (0.95) at 21 days with 50mM of GBH in A. flavus and 20 and 50mM of GBH in A. parasiticus. These results show that, even though Aspergillus section Flavi growth did not increase, AFB₁ production increased on maize grains at GBH concentrations similar to those of field recommended doses under favorable water availability and temperature conditions.