Atividade antifúngica de extratos vegetais dos frutos de Pterodon pubescens em Bipolaris oryzae

Abstract

Bipolaris oryzae is the causative agent of brown spot. This disease affects rice crops all over the world and is spread by seeds contaminated by coleoptiles. When brown spot is not efficiently controlled in rice crops, it can cause up to 90% of production to be lost. In this context, the present study obtained plant extracts from the fruits of Pterodon pubescens (sucupira-branca) using the cold extraction process by means of sonication using solvents of different polarities. Hexane, dichloromethane, ethyl acetate and ethanol were used for the extraction, and the yields of the plant extracts were: 14.69; 15.03; 14.43 and 15.18 respectively. The antifungal activity was determined on B. oryzae strain BRM 67786 (Embrapa). The antifungal activity test used was disk diffusion on a plate; the extracts were prepared in four concentrations (250 μg.mL-1 , 500 μg.mL-1 , 750 μg.mL-1 and 1000 μg.mL-1 ) and the mycelial growth halo was measured after seven and 14 days. Increasing the polarity of the extracting solvents influenced the color and consistency of the extracts, but there was no significant difference in the yield of the extracts. The extract obtained with the ethyl acetate solvent showed the greatest inhibition effect, the extract managed to inhibit more than 45% of the mycelial growth halo, while the extract obtained with the hexane solvent proved to be less efficient at inhibiting the growth of the mycelial halo. The medium-polarity extracts obtained from the fruits of P. pubescens have the potential to inhibit the mycelial halo of B. oryzae.