The effects of glyphosate on the in vitro linear growth of selected microfungi from a boreal forest soil

Abstract

Glyphosate-based herbicides are used extensively in forestry and agriculture to control broadleaf plant competition. A review of the literature offers conflicting results regarding the impact of glyphosate on fungal growth. This study investigated the effects of 7 glyphosate concentrations (1, 2, 5, 10, 50, 100, and 1000 µg·mL–1) of Roundup (35.6% glyphosate) on the number of colony-forming units (CFUs) of soilborne microfungi from a boreal forest soil sample and on the in vitro linear growth of 20 selected species of microfungi representative of this boreal forest soil. Concentrations of glyphosate at 50 µg·mL–1and higher significantly decreased the number of CFUs observed. At glyphosate concentrations equal to 5 µg·mL–1, 13 fungal species exhibited colony diameters less than 50% than that of their respective controls. Several species showed an inhibition of pigmentation and sporulation when subjected to glyphosate concentrations of 1 µg·mL–1. Differential sensitivity was observed among species at the various concentrations, suggesting the possibility of a shift towards tolerant species of fungi when they are exposed to glyphosate.