Fungos endofíticos e extratos vegetais no controle alternativo da mancha-alvo do tomateiro

Abstract

Secondary metabolites present in endophytic fungi and medicinal plants have several biological properties, including antifungal activity. In this context, 141 endophytic fungi isolated from guaraná leaves and seeds (Paullinia cupana Kunth), crude aqueous extracts of leaves of Picrolemma sprucei Hook.f (caferana), Croton cajucara Benth. (sacaca), Piper marginatum Jacq. (caapeba) and rhizome of Curcuma zedoaria (Christin.) Rosc (curcuma) prepared at the concentrations of 0 %, 10 %, 20 %, 30 %, 40 % and 50 %, and hexanic, ethyl acetate and methanolic fractions phytopathogen Corynespora cassiicola. Thirteen endophytic isolates showed inhibition between the antagonist and the pathogen, whereas the isolates 3012 R1 and 3031 R2 presented the highest inhibition value, showing their potential for future studies on the biocontrol of fungi of the genus Corynespora. In vitro bioassays (mycelial growth, sporulation, spore germination, direct bioautography and minimal inhibitory concentration) and in vivo (effect of the crude aqueous extract of P. marginatum on tomato seedlings) showed that the hexane and ethyl acetate fractions of P. marginatum reduced mycelial growth, sporulation and germination of the pathogen, and that the crude extract of P. sprucei presented the highest percentages of inhibition of these variables. In direct bioautography, zones of inhibition of mycelial growth were detected in the hexanic and acetate-ethylic fractions of P. marginatum, which presented a minimum inhibitory concentration (MIC) of 2.5 mg.mL-1. The in vivo test showed that control of the target spot in tomato was not feasible under the tested conditions of the crude extract of P. marginatum.