Fungitoxidade de extratos de secreções de sapos sobre fitopatógenos isolados de Crotalária

Abstract

The work was executed using extract of glandular secretions from two species of frogs, named Substance 1 (S-1) and Substance 2 (S-2), in concentrations of 0,1 to 0,5 mg/mL. The plant pathogens, Choanephora infundibulifera, Sclerotium sp, Fusarium udum and Curvularia sp. were isolated from infected plants of crotalaria. In vitro test, the mycelial growth was performed using S-1 and S-2 extracts, distilled water (negative control) and epoxiconazole + pyraclostrobin (positive control). In Petri dishes (ø 8 cm) containing PDA medium, were added four filters of papers disks (6mm) with the treatments, and in the center of the plate were added the mycelium discs of the pathogens. After 48h began the assessment of mycelial growth, until the colony reaches 2/3 of the plate. The counting of spores of F. udum and Curvularia sp. was made with a Neubauer Chamber and the couting of sclerotias of Sclerotium sp., visually. The test of spores germinating of F. udum and Curvularia sp. was performed in ELISA plates, was added 40μL of suspension of spores (5x10 4 conídias/mL) and 40μL of the treatments. After 24 hours, the germinating was stopped with methylene blue, 20μL. Was counted 100 spores by repetition. In the test with S-2, the concentration 0,2mg/ml inhibited the mycelial growth of Sclerotium sp., F. udum and C. infundibulifera, and concentrations 0,3mg/mL and 0,5 mg/mL inhibited, Sclerotium sp. and C. infundibulifera, respectively.S-2 also, inhibited the germination of spores of F. udum at all concentrations, and spores of Curvularia sp. at concentrations of 0,3 to 0,5mg/ml. The treatment S-1 inhibited the germination of spores of F. udum at concentrations 0,4 and 0,5 mg/mL. It was concluded that, extract of glandular secretions of S-2 shows antifungal activity against C. infundibulifera, Sclerotium sp., Curvularia sp. and F. udum and S-1 shows antifungal activity under F. udum.