Anais do Congresso Paranaense de Microbiologia
IV Congress of Microbiology in Paraná

The fungus Fusarium oxysporum f.sp phaseoli is the causative agent of the disease known as fusarium wilt in common bean (Phaseolus vulgaris). The disease is capable of drastically reducing plant growth, compromising up to 70% of productivity. The growing resistance of phytopathogenic fungi to agrochemicals, highlights the importance of the search for new bioactive molecules. The objective of this work was to evaluate the antifungal action of the F4A fraction, produced by the secondary metabolism of the LV strain of Pseudomonas aeruginosa, against the fungus in question. The LV strain was cultivated in nutrient broth supplemented with 5mg/L of CuCl2, pH:6.8, 28°C, under forced aeration. After 10 days of cultivation, the broth was centrifuged (9,000 rpm, 15 min, 4 °C) to remove the cells. The supernatant was concentrated to approximately 1/20 of its initial volume in a ventilated oven at 60°C. To extract the compounds of interest, the concentrate was subjected to liquid-liquid partition with dichloromethane in a 2:1 ratio (v:v; dichloromethane: supernatant). The extract called dichloromethane phase (FD) was concentrated in a rotaevaporator at 45 °C. The FD phase was fractionated by vacuum liquid chromatography (CLV) in a glass column (20 mm in diameter, 350 mm in height) filled with silica gel 60 (0.063 - 0.200 mm, Merck), coupled to a vacuum pump at 300 mmHg. The mobile phase was constituted by an organic solvent sequence in increasing polarity scale, according to PISTORI et al. (2018). F4A corresponds to the seventh fraction isolated during the aforementioned process. The antifungal activity of F4A was evaluated using the disk diffusion test at three different concentration of 10, 40, and 60µg/disk. Each disc was placed on seeding (200µL) of conidia suspension (1x107 conidia per mL) in PDA (Potato Dextrose Agar), poured into a Petri dish, and incubated at 28°C in BOD. The halo of inhibition was measured, in mm, on the fourth day. According to the results observed, the discs promoted inhibition halos of 3, 5, and 18mm at concentrations of 10, 40, and 160µg/disc, respectively. Currently, our research group seeks to enable the application of F4A in field conditions as an alternative for the control of this disease.