Citronella essential oil in the control and activation of coffee plants defense response against rust and brown eye spot

Abstract

The rust and brown eye spot are the main coffee diseases. The losses are due to intense defoliation of plants, which has reduced its production and longevity. The brown eye spot also occurs in fruits, with negative effects on the beverage quality. Some essential oils have presented promising results in the control of plant diseases, as an alternative to the use of fungicides. The objective of this study was to evaluate citronella essential oil in the control of rust and brown eye spot and in the activation of coffee plants defense responses. Twelve-month-old plants were sprayed with citronella oil 1000 μL L -1 , acibenzolar-S-methyl 200 mg L -1 and tebuconazole fungicide 200 mg L -1 . Plants were inoculated with Hemileia vastatrix and Cercospora coffeicola seven days later. The application was repeated after 30 days. Plants with five months were sprayed with the same treatments to assess the induced defense responses. Citronella oil controlled rust and brown eye spot with efficiencies of 47.2% and 29.7%, respectively, while tebuconazole presented control of 96.5% and 90.5%, respectively. Acibenzolar-S-methyl reduced brown eye spot by 55.9% and showed no significant control of rust. Citronella oil increased peroxidase and chitinase activities in five months coffee plants 336, and 24 and 336 hours after spraying, respectively. Acibenzolar-S-methyl increased peroxidase, chitinase and β -1,3-glucanase activities 192, 288 and 336; 24 and; 240 hours after spraying, respectively. The treatments did not increase accumulation of phenols, but a significant increase in lignin was observed in plants sprayed with citronella oil.

A ferrugem e a cercosporiose são as principais doenças de cafeeiro. Os prejuízos se devem a intensa desfolha das plantas que têm sua produção e longevidade reduzidas. A cercosporiose também ocorre nos frutos, com reflexos negativos na qualidade da bebida. Alguns óleos essenciais têm apresentado resultados promissores no controle de doenças em plantas, em alternativa ao uso de fungicidas. Neste trabalho, objetivou-se avaliar o óleo essencial de citronela no controle da ferrugem e cercosporiose e na ativação de respostas de defesa em cafeeiro. Plantas com 12 meses foram pulverizadas com o óleo de citronela 1.000 μL L -1 , acibenzolar-S-metil 200 mg L -1 e fungicida tebuconazole 200 mg L -1 e inoculadas com Hemileia vastatrix e Cercospora coffeicola sete dias após. Repetiu-se a aplicação após 30 dias. Plantas com cinco meses foram pulverizadas com os mesmos tratamentos para avaliar as respostas de defesa induzidas. O óleo de citronela controlou a ferrugem e a cercosporiose com eficácias de 47.2% e 29,7%, respectivamente, enquanto tebuconazole apresentou controles de 96,5% e 90,5%, respectivamente. Acibenzolar-S-metil reduziram em 55,9% a cercosporiose da ferrugem e não apresentou controle significativo da ferrugem. O óleo de citronela aumentou as atividades de peroxidase e quitinase em mudas de cafeeiro 336 e; 24 e 336 horas após pulverização, respectivamente. Acibenzolar-S-metil aumentou as atividades de peroxidase, quitinase e β -1,3-glucanase 192, 288 e 336 e; 24 e; 240 horas após pulverização, respectivamente. Os tratamentos não promoveram aumento de fenóis, mas aumento significativo no teor de lignina foi observado em plantas pulverizadas com óleo de citronela.