Survey of Aspergillus section Flavi presence in agricultural soils and effect of glyphosate on nontoxigenic A. flavus growth on soil-based medium

Abstract

Aims: To evaluate the cultivable mycobiota from agricultural soils exposed to pesticides, the aflatoxigenic capacity of Aspergillus section Flavi strains and the effect of glyphosate on lag phase and growth rates of native nontoxigenic Aspergillus flavus under different water potential (MPa) conditions on soilbased medium. Methods and Results: Culturable mycobiota analysis from different agricultural soils was performed by the surface spread method. The effect of glyphosate (0-20 mmol l À1 ) on the growth of A. flavus strains was evaluated on a soil extract solid medium. Mycobiota analysis of crop soils showed the presence of twenty-one genera of filamentous fungi. Aspergillus flavus and Aspergillus niger aggregate strains were isolated from the three soil types. Ninety-two per cent of A. flavus strains were toxigenic. In vitro assay results showed that at À0Á70 MPa, a significant increase in growth rate in all strains was recorded at 5 and 20 mmol l À1 of glyphosate. At À2Á78 MPa, this parameter remained constant at all glyphosate concentrations, except in GM4 strain where an increase in growth rate was recorded with increasing pesticide concentrations. At À7Á06 MPa, a significant increase in growth rate has also been observed in GM 3 strain with 5 mmol l À1 and in GM 4 strain with 10 and 20 mmol l À1 . Conclusions: This study showed that the imperfecti fungi Aspergillus spp., Penicillium spp., Trichoderma spp., Cladosporium spp. and Paecilomyces spp. are isolated as prevalent groups in agricultural soil exposed to pesticides, and the capacity of nontoxigenic A. flavus strains to tolerate different glyphosate concentrations under different water potential (MPa) conditions. Significance and Impact of the Study: This manuscript makes a contribution to the knowledge of cultivable fungal populations from agricultural soils exposed to pesticides and the glyphosate tolerance of A. flavus strains.

Evaluation of Chlorpyrifos Tolerance and Degradation by Non-Toxigenic Aspergillus Section Flavi Strains Isolated from Agricultural Soils

“…In a previous work we evaluated the tolerance to three pesticides (among them chlorpyrifos) of Aspergillus section Nigristrains in soil-based medium (Carranza et al, 2014). Unlike the results observed in the present study, significant decreases in the growth rate of Aspergillus section Nigri strains with increasing chlorpyrifos concentrations (5, 10 and 20 mg L -1 ) were observed.…”

“…All strains tested were able to develop at the highest concentration assayed (500 mM) regardless the water availability condition (Carranza et al, 2016a). In addition, Aspergillus section Nigri strains also isolated from these soils, resulted tolerant to chlorpyrifos (Carranza et al, 2014). However, there is no information about chlorpyrifos tolerance or degradation by Aspergillus section Flavi strains isolated from these soils.…”

“…Three A.oryzae strains (AM 1, AM 2 and GM 3) and one A.flavus (GM 4) previously identified by molecular methods were used (Carranza et al, 2016a).These strains were previously isolated from fields destined to maize and soybean production (Carranza et al, 2014). These fields have been exposed to successive applications of pesticides during the last decade.…”

“…These fields have been exposed to successive applications of pesticides during the last decade. The ability of the strains tested to produce aflatoxins and cyclopiazonic acid was evaluated previously (Barberis et al, 2012;Carranza et al, 2014); and they resulted non-toxigenics. The strains belong to our culture collection at the Department of Microbiology and…”

“…is one of the most prevalent genera isolated from Argentinean agricultural soils (Carranza et al, 2014;2016a). Being Aspergillus section Flavi strains isolated in major frequency.…”