Patogenicidade, efeito da temperatura no desenvolvimento e controle de isolados de Colletotrichum gloeosporioides, agente causador da antracnose da juçara (Euterpe edulis Mart.)

Abstract

The juçara palm tree (Euterpe edulis), native from the Atlantic Rainforest biome, has an enormous ecological and economic potential. It is used only to the production of palm, but its disordered exploration takes this palm species to risk of extinction. Due to this reason, several studies are being conducted in order to discover methods of extraction without destroying the plant. Recently more attention has been given to its fruits to pulp production similar to that açai produced in the Brazilian Amazon, however, with higher nutritional indexes. There are few studies of the diseases that attack the juçara palm tree. The main disease already reported is the anthracnose, which cause defoliation, dieback and fruit rotting. As the physiological characteristics of the isolates of the fungus Colletotrichum gloeosporioides in juçara are unknown, this study aimed to evaluate the pathogenicity of different isolates obtained from four locals of the municipalities of Paraty (RJ) and Ubatuba (SP), to evaluate the effect of temperature on the fungal development, in order to know the ideal temperature for the development of the pathogen on these locals, and evaluate the viability to use the essential oils in the control in vitro of C. gloeosporiodes. The experiments were carried out in the laboratory of Plant Pathology at the Universidade Federal Rural do Rio de Janeiro (Seropédica, RJ, Brazil). The growth of four isolates in vitro were evaluated under six temperatures at 20ºC, 25ºC, 28ºC, 30ºC, 32ºC, and 35ºC, using BOD chamber, with five replications. The optimal temperature for fungal growth was 28ºC for all isolates evaluated. Based on this temperature, tests in vitro was performed with essential oils of the botanical species: spiked pepper (Piper aduncum), clove (Caryophyllus aromaticus), and neem (Azadirachta indica) at different concentrations: 0, 100, 250, 500, 750, 1000, 1250 1500 μg/ml in order to evaluate the fungitoxic effect of these oils on the growth of C. gloeosporioides for seven days. It was observed that the oil of clove has higher fungitoxic effect than the other oils evaluated, inhibiting the mycelial growth at the lowest concentration (100 μg/ml), and followed by the oil of Piper aduncum. The neem oil showed partial inhibition of mycelial growth at all the concentrations evaluated.