Eficiência da filtração lenta na redução da infestação por Fusarium sp. na solução nutritiva

Abstract

Fusarium sp. is a common phytopathogenic fungus in various crops, causing diseases that can compromise plant development and productivity. This study aimed to evaluate the efficiency of slow sand filtration, with and without UV radiation, in controlling Fusarium sp. in irrigation water for application in nutrient solution in closed hydroponic systems. The experiment was conducted at Embrapa Agroindústria Tropical in Fortaleza (Brazil), using a slow sand filter with a capacity of 200 liters of water, an average flow rate of 100 L/h, a medium grain size (0.42 to 1.20 mm in diameter), and a 25 W UV filter. A factorial arrangement (3×5) was used, with the filtration type factor at three levels (no filtration, slow sand filtration, and slow sand filtration with UV radiation) and the filtration time factor at five levels (0, 1, 2, 3, and 4 hours). Fusarium sp. was isolated from bell pepper (Capsicum annuum) roots showing symptoms of root necrosis. A suspension of fungal spores was inoculated into 100 liters of irrigation water, reaching a final concentration of 1 × 10^4 spores/mL, and then introduced into a slow sand filter. Water samples were collected from the filter influent and effluent and subsequently distributed using the Spread Plate technique in Petri dishes containing PDA (potato dextrose agar) medium. After a five-day incubation period, colony counts were performed. The results showed that only the positive control samples presented significant growth of Fusarium sp. colonies, while the samples after slow sand filtration and slow sand filtration with UV did not show significant growth. It is concluded that slow sand filtration, either alone or combined with UV radiation, is efficient in the disinfestation of Fusarium sp., with an efficiency greater than 99%.