ABSTRACT
The use of antibiotics in agriculture is limited when compared to their applications in human and veterinary medicine. On the other hand, the use of antimicrobials in agriculture contributes to the drug resistance of human pathogens and has stimulated the search for new antibiotics from natural products. Essential oils have been shown to exert several biological activities including antibacterial and antifungal actions. The aim of this study was to determine the activity of 28 essential oils from medicinal plants cultivated at CPMA (Medicinal and Aromatic Plants Collection), CPQBA/UNICAMP, against Colletotrichum gloeosporioides (Penz.) Sacc., the anthracnose agent in yellow passion fruit (Passiflora edulis Sims f. flavicarpa Deg), as well as evaluating their effect in the control of post-harvest decay. The oils were obtained by water-distillation using a Clevenger-type system and their minimal inhibitory concentrations (MIC) determined by the micro-dilution method. According to the results, 15 of the 28 essential oils presented activity against Colletotrichum gloeosporioides, and the following four oils presented MIC values between 0.25 and 0.3 mg/mL: Coriandrum sativum, Cymbopogon citratus, Cymbopogon flexuosus and Lippia alba. The evaluation of Cymbopogon citratus essential oil in the control of post-harvest decay in yellow passion fruit showed that the disease index of the samples treated with the essential oil did not differ (P < 0.05) from that of the samples treated with fungicide. The present study shows the potential of Cymbopogon citratus essential oil in the control of the anthracnose agent in yellow passion fruit.
Subject(s)
Food Contamination/analysis , Microbial Sensitivity Tests , Plant Oils/analysis , Plant Structures , Plants, Medicinal , Food Samples , Methods , Passiflora , MethodsABSTRACT
Citrus fruits are affected by the black spot disease caused by Guignardia citricarpa. Resistance induction is an alternative control measure and chitosan exhibits potential as resistance inducer. The effect of chitosan on G. citricarpa was evaluated in vitro and in 'Valencia' oranges. Citrus fruit were immersed into different chitosan concentrations. Chitosan (2 percent), combined with or without thiabendazole and the citric acid was also investigated. All the chitosan concentrations inhibited G. citricarpa mycelial growth and affected morphologically the conidial germination and appressorium formation. Chitosan inhibited the development of new lesions in oranges at room condition or under refrigeration. Thiabendazole and citric acid did not reduce the formation of lesions. Biochemical analysis revealed that chitinase, β-1,3-glucanase, peroxidase and polyphenoloxidase activities were increased in chitosan-treated fruits. Thus, the effect of chitosan on the reduction of black spots in 'Valencia' oranges could be due to the germicidal effect on the pathogen and/or resistance induction in the fruit.
Frutos cítricos são afetados pela mancha preta dos citros, causada por Guignardia citricarpa.A indução de resistência é uma alternativa de controle e a quitosana exibe potencial como indutor de resistência. O efeito da quitosana sobre G. citricarpa foi avaliado in vitro e em laranjas 'Valência'. Frutos cítricos foram imersos em diferentes concentrações de quitosana. Quitosana (2 por cento), associada ou não com tiabendazol e ácido cítrico, foi também avaliada. Todas as concentrações de quitosana inibiram o crescimento micelial de G. citricarpa e afetaram morfologicamente a germinação dos conídios e a formação de apressórios. Quitosana inibiu o desenvolvimento de novas lesões em laranjas em condições ambiente e sob refrigeração. Tiabendazol e ácido cítrico não reduziram o aparecimento de novas lesões. Análises bioquímicas revelaram que atividades de quitinase, β-1,3-glucanase, peroxidase e polifenoloxidase aumentaram em frutos tratados com quitosana. Portanto, a capacidade da quitosana na redução da mancha preta em laranja 'Valência' pode ser devida ao efeito germicida sobre o patógeno e/ou a indução de resistência no tecido do fruto.
ABSTRACT
Laranjas 'Pêra' foram submetidas a tratamento pós colheita por imersäo durante um minuto em soluções de imazalil (Magnate 500 CE), tiabendazole (Tecto 600PM) e mistura de ambos, em diferentes concentrações. Após o tratamento as amostras foram armazenadas durante 28 dias