Native mycota in agricultural soils exposed to pesticides and Aspergillus oryzae tolerance to chlorpyrifos in microcosms assays

Abstract

Chlorpyrifos (CPF) constitutes a class of older and riskier pesticides, with more than 50 years of use. After pesticide application, a low percentage reaches the target and the rest remain in the environment. Due to this, bioremediation strategies are being increasingly studied. The aims of the present study were to determine the competitiveness and the permanence of a non-toxigenic, CPF-degrading A. oryzae (AM 1) strain in agricultural soil microcosms. These microcosms were contaminated with commercial formulation of CPF (10, 20 and 50 mM) and conditioned at two water holding capacity (70 and 30 WHC). In addition, Aspergillus section Flavi counts of soils of three localities of southern Córdoba Province were evaluated, due to these soils were used to prepare the microcosms. In the microcosm's assays, together with the native mycota, A. oryzae was isolated from all the treatments and conditions assayed. Thus this strain was able to tolerate the different doses of CPF tested. Regarding the native mycota, Aspergillus sp., Trichoderma sp., Penicillium sp., Cladosporium sp. and Fusarium sp. were the most frequent genera isolated from the microcosms. The CPF treatments influenced in different ways the counts of the most frequent genera isolated. This study allowed knowing the in situ survival, under optimal and not optimal humidity conditions, of a CPF-degrading fungal strain in presence of the native mycota. These results are very important because the permanence in the environment of a potentially bioremediation agent is one of the main characteristic that must be evaluated.