Efeito de fosfito de potássio no crescimento e na densidade micelial do Fusarium solani do maracujazeiro

Abstract

The aim of this study was to evaluate the effect of potassium phosphite on the mycelial growth and density of F. solani isolated from passion flower vines. Verification of the potassium phosphite effect on F. solani consisted in diluting 0, 1, 10, 50, 100, 250, 500, 750 and 1000 ppm of the product in PDA medium, subsequently evaluating the mycelial growth and density of the fungus. Influence of the pH of the PDA medium on F. solani growth was tested by diluting hydrochloric acid in the medium until the obtained pH values were identical to those of the plates containing the potassium phosphite concentrations. After ten days of incubation, fungal growth was measured. F. solani mycelial density was measured by reading the absorbance at 405 nm of discs containing fungal mycelium in an ELISA reader. The fungicide or fungistatic effect of potassium phosphite was tested by transferring F. solani, from the concentrations that had inhibited it, to pure PDA medium and by observing whether there was further growth or not. Potassium phosphite significantly inhibited the mycelial growth and density of F. solani, from 50 ppm. There was not any significant difference in F. solani growth within the tested pH range. F. solani grew on pure PDA medium, after its transference from the culture medium containing the potassium phosphite concentration that had inhibited it, which indicates a fungistatic effect on the fungus.