Avaliação do Efeito do Extrato Etanólico de Piper umbellatum L. no Controle Alternativo de Rhizoctonia solani e Macrophomina phaseolina

Objetivou-se, neste trabalho, investigar o potencial do extrato da planta Piper umbellatum (Sin. Piper umbellata L.) no crescimento micelial de Rhizoctonia solani e Macrophomina phaseolina. Para avaliacao das habilidades fungicida e ou fungistatica, os fungos fitopatogenicos foram crescidos previamente em meio de cultura BDA (batata dextrose agar), tendo sido  realizado o teste de crescimento micelial, em meio de cultura BDA nas concentracoes de 800, 1200, 1600, 2000 e 2400 µg 100 mL-1. Foram vertidos 10 mL de meio das diferentes concentracoes em placas de Petri, com quatro repeticoes para cada concentracao. A avaliacao do crescimento micelial para todos os patogenos foi realizada por medidas diarias do diâmetro das colonias. Na prospeccao fitoquimica do extrato etanolico de P. umbellatum foi detectada a presenca majoritaria de compostos fenolicos (100%), seguido dos flavonoides, esteroides e alcaloides (75%), os taninos, triterpenos e acucares redutores (50%) e com menor frequencia as saponinas (25%). As concentracoes testadas nao inibiram o crescimento micelial dos fungos, no entanto se observou que houve interferencia no desenvolvimento da colonia de R. solani, pois nao foi observada a formacao de micro esclerodios, estruturas estas formadas na testemunha e em funcao da presenca de metabolitos secundarios no extrato que podem apresentar atividade antifungica, e recomendavel a continuacao do estudo fitoquimico de P. umbellatum, para isolamento e identificacao de substâncias responsaveis pela atividade e determinar suas fracoes ativas, visando o controle de agentes fitopatogenicos.   Palavras-chave: Plantas Fungicidas. Piperaceae. Estratos Vegetais. Rhizoctonia solani; Macrophomina phaseolina.       Abstract The objective of this work was to investigate the potential of Piper umbellatum (Sin. Piper umbellata L.) plant extract on the mycelial growth of Rhizoctonia solani and Macrophomina phaseolina. To evaluate fungicidal and or fungistatic abilities, phytopathogenic fungi were previously grown in BDA culture medium (potato dextrose agar), mycelial growth test was performed in BDA culture medium at concentrations of 800, 1200, 1600, 2000 and 2400 µg 100 mL -1. 10 mL of medium of the different concentrations were poured into Petri dishes, with four replicates for each concentration. Mycelial growth evaluation for all the pathogens was performed by daily measurements of colony diameter. Phytochemical prospecting of P. umbellatum ethanolic extract showed the presence of phenolic compounds (100%), followed by flavonoids, steroids and alkaloids (75%), tannins, triterpenes and reducing sugars (50%) and less frequently. the saponins (25%). The tested concentrations did not inhibit the mycelial fungi growth, however, it was observed that there was interference in the development of R. solani colony, as  the formation of micro sclerodes, structures formed in the control was not observed and due to the presence of secondary metabolites. In the extract that may present antifungal activity, the continuation of the phytochemical study of P. umbellatum is recommended for isolation and identification of substances responsible for the activity and to determine their active fractions, aiming at the control of phytopathogenic agents.   Keywords: Fungicidal plants; Piperaceae; Plant extracts; Rhizoctonia solani; Macrophomina phaseolina.