Fungicidal activity of extracts of Piper sp. against fungi Rhizoctonia solani and Sclerotium rolfsii

Abstract

The search for mechanisms that may help in the control of phytopathogens has been recurrent, having as a source the biological diversity, due to its variability, providing compounds with diverse pharmacological action, such as in the fight against microorganisms. Studies report the use of extracts against phytopathogenic fungi in order to maintain a balance of these pathogens, as they cause great damages in several agricultural crops. Therefore, this work aims to test extracts of Piper sp. against the fungi Rhizoctonia solani and Sclerotium rolfsii, pathogens of extreme importance in the bean crop. In this way, stems and leaves of Piper sp. were collected in the greenhouse of Embrapa Rondônia. Extracts, in the proportion 1:10 (w/v, g/mL), were obtained in extraction solution 0.1 M PBS buffer. The extracts were added to the semi-solid BDA medium in the ratio 1/100 (V/V) and then homogenized and poured into petri dishes. In the center of the plates, mycelial discs of the pathogens were deposited, being sealed and incubated in chamber B.O.D. for up to 96 hours, under controlled temperature and photoperiod conditions. Fungal growth evaluations were performed daily, using a pachymeter, from the second day of incubation until control group plates measurement, with PBS buffer, reached total growth. The antifungal activity of the extracts was also evaluated in an in vivo experiment conducted under greenhouse conditions. For that, bean seedlings were inoculated with the pathogens and tested with different concentrations of Piper sp. Six concentrations were evaluated, with 5 replicates per treatment. As controls, 0.1 M PBS buffer and Amistar and Vitavax fungicides were used, as recommended. From the extracts tested, stem extract promoted inhibition of R. solani growth statistically superior to that of the commercial fungicide, whereas against S. rolfsii, although the extract was efficient, the effect was lower than that of the tested fungicide. This work allows to infer that extracts of Piper sp. presented significant activities against the fungi Rhizoctonia solani and Sclerotium rolfsii. Further testing will be performed to verify its in vivo efficiency (field).