Avaliação da sensibilidade in vitro de isolados de Colletotrichum lindemuthianum a fungicidas

Abstract

Colletotrichum lindemuthianum (Sacc. & Magn.) Scrib. e o agente causal da antracnose do feijoeiro (Phaseolus vulgaris L.), doenca fungica de grande importancia para a cultura, pois pode causar perdas de ate 100% na producao, quando sao utilizadas cultivares suscetiveis e sementes infectadas, sob condicoes ambientais favoraveis ao desenvolvimento de epidemias. O presente trabalho objetivou avaliar a sensibilidade in vitro de 20 isolados de Colletotrichum lindemuthianum, provenientes de diferentes regioes do pais, a cinco fungicidas de diferentes principios ativos e algumas misturas (carbendazin, chlorothalonil, tiofanato metilico, chlorothalonil + tiofanato metilico, trifloxystrobin, propiconazol, trifloxystrobin + propiconazol), em cinco diferentes concentracoes (0, 1, 10, 100 e 1000 -Êg.mL-1) adicionados em meio de cultura batata-dextrose-agar (BDA). Os isolados cresceram por sete dias a 25 -C no meio de cultura BDA e apos esse periodo, discos de 0,5 cm de micelio do fungo, foram transferidos para placas de Petri com o meio BDA contendo as diferentes concentracoes de fungicidas. As placas foram incubadas por sete dias a 25 -C, avaliado o crescimento medio do diametro das colonias (em cm) e calculado os valores de porcentagem de inibicao do crescimento micelial dos isolados em relacao ao tratamento testemunha. Os resultados mostraram que para os fungicidas carbendazin e tiofanato metilico, 11 isolados fungicos foram totalmente ou parcialmente inibidos na concentracao de 1 ou 10 -Êg.mL-1. Chlorothalonil mostrou-se menos eficiente que os demais produtos pelo fato de inibir o crescimento micelial de apenas tres isolados na concentracao de 1000 -Êg.mL-1. A mistura de chlorothalonil e tiofanato metilico mostrou a inibicao total do crescimento micelial de quatro isolados a 1 -Êg.mL-1, e, a 1000 -Êg.mL-1, oito isolados mostraram-se sensiveis a mistura desses produtos...

Colletotrichum lindemuthianum (Sacc. & Magn.) Scrib. is the causal agent of anthracnose in bean (Phaseolus vulgaris L.). This fungal disease has great importance in the crop, since it may cause yield losses of up to 100% when susceptible cultivars and infected seeds are used under environmental conditions that favor the development of epidemics. The aim of this work was to evaluate the in vitro sensitivity of 20 isolates of Colletotrichum lindemuthianum from different regions of the country, to five fungicides with different active principles and some mixtures (carbendazim, chlorothalonil, methyl thyophanate, chlorothalonil + methyl thyophanate, trifloxystrobin, propiconazole, trifloxystrobin + propiconazole), at five different concentrations (0, 1, 10, 100, and 1000 ìg.mL-1), added to potato-dextrose-agar (PDA) culture medium. The isolates were cultured for seven days at 25 °C in PDA medium, after which 0.5 cm disks of fungal mycelium were transferred to Petri dishes containing PDA medium and the various concentrations of fungicides. The Petri dishes were incubated for seven days at 25 °C. We evaluated the mean growth in diameter of the colonies (in cm) and calculated percentage values for mycelial growth inhibition of the isolates in relation to the control treatment. The results showed that 11 fungal isolates were completely or partially inhibited by the fungicides carbendazim and methyl thyophanate at concentrations of 1 or 10 ìg.mL-1. Chlorothalonil proved less effective than the other products, as it inhibited mycelial growth in only three isolates, at the concentration of 1000 ìg.mL-1. The chlorothalonil and methyl thyophanate mixture showed complete mycelial growth inhibition in four isolates at 1 ìg.mL-1, while eight isolates were sensitive to the mixture of these products at 1000 ìg.mL-1. The propiconazole and trifloxystrobin mixture was the most effective and inhibited growth... (Complete abstract click electronic access below)