Influence of glyphosate on growth parameters of Aspergillus parasiticus strains isolated from soil on in vitro assay.

BARBERIS C.L.; CARRANZA M.C.; CHIACCHIERA S.M.,; MAGNOLI C.E,

Mendoza

Congreso; Mycored- Argentina. Strategies to rteduce the impact of mycotoxins in Latin America in a global contex.,; 2011

Universidad Nacional de Río Cuarto

The organophosphonates as glyphosate are biogenic and xenobiotic compounds characterized by the presence of a stable carbon to phosphorus (C-P) bond. The C-P bond imparts upon these molecules a relative resistance to degradation and concern has been expressed over their environmental impact and possible ecotoxicity. The species of Aspergillus section Flavi as A. flavus and A. parasiticus produce secondary metabolites such as aflatoxins. Soil act as a reservoir for these species and these fungi can invade agricultural commodities such as corn, soybeans, peanuts, and cottonseed. The aim of the present study was to evaluate the effect of the herbicide glyphosate on (i) lag phase before growth and (ii) growth rate of A. parasiticus strains on corn meal extract agar under different environmental conditions. Four strains of A. parasiticus were used in these experiments (AP43, AP45, AP55 isolated from soil and the reference strain NRRL 2999). Corn meal extract agar (CMEA) was used at 3%. The aW of the basic medium was adjusted to 0.98, 0.95 and 0.93 with the addition of glycerol, the medium was autoclaved at 120ºC for 20 min. Before cooling to 50ºC different levels of glyphosate (0.5, 1.0, 1.5, 2.0, 5.0 and 10 mM) were added. The plates were centrally needle-inoculated and incubated for 30 days at 25ºC. All the treatments were done by triplicate and repeated three times. Two diameters of the colony at right angles to each other were measured. The radius of the colony was plotted against time, and a linear regression was applied in order to obtain the growth rate. The lag phase was obtained by extrapolation of this line to the x axis. In the control treatments there were a parallelism between the increment of lag phase and the reduction of growth rate when aW decreased for all strains. In the control treatments there were a parallelism between the increment of lag phase and the reduction of growth rate when aW decreased for all strains assayed. The glyphosate showed a further decrease in the lag phase at highest concentrations. A significant increase in growth rate was observed from 2 mM of herbicide at all aW levels assayed. At 0.5 and 1.0 mM and 0.98 aW, the glyphosate not affected significantly the growth parameters in all strains tested. These results suggest that determined concentrations of glyphosate could promote in vitro the growth of A. parasiticus strains.