Efeito do tratamento de sementes de pimentão com óleos essenciais sobre o controle de Colletotrichum gloeosporioides e o potencial fisiológico das sementes
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Data
2017-02-21
Autores
Nascimento, Daniele Maria do [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O pimentão (Capsicum annum L.) é uma das hortaliças mais consumidas no mercado brasileiro, contudo, uma importante doença fúngica, a antracnose, pode dizimar todos os seus frutos em campo, caso ocorram condições favoráveis ao seu estabelecimento. A antracnose é causada por um complexo de espécies do gênero Colletotrichum, podendo o fungo ser transmitido via semente, constituindo-se essa em um importante meio de introdução e disseminação do patógeno em novas áreas. O tratamento das sementes torna-se, então, uma medida importante no manejo e controle desta doença. Visando diminuir a aplicação de produtos químicos, a pesquisa por substâncias naturais com ação antifúngica vem sendo estimulada. Neste trabalho, foi investigada a ação de oito óleos essenciais (alecrim, citronela, cravo, copaíba, eucalipto, hortelã, manjericão e tea tree) sobre Colletotrichum gloeosporioides, isolado do pimentão. Inicialmente, foi avaliada a atividade in vitro dos óleos essenciais sobre o fungo, adicionando-os ao meio de cultura batata-dextrose-ágar (BDA) contido em placas de Petri, nas concentrações 0,25%, 0,50% e 0,75%. Em seguida, o fungo foi transferido para o centro de cada placa de Petri contendo os tratamentos. O experimento foi conduzido em delineamento inteiramente casualizado, segundo o esquema fatorial 8x3 (oito óleos essenciais x três concentrações), e um tratamento testemunha (composto por BDA puro), e três repetições. O experimento foi conduzido em duplicata. As placas foram mantidas a 22°C e fotoperíodo de 12 horas. Para verificar o efeito dos óleos essenciais, o crescimento micelial (diâmetro das colônias), a porcentagem de inibição do crescimento (PIC) e a esporulação (número de esporos/mL) foram avaliados. Nos dois ensaios, os óleos essenciais de cravo, citronela, eucalipto, hortelã e manjericão, independente da concentração empregada, inibiram totalmente o patógeno, não permitindo a esporulação deste. A segunda etapa do trabalho objetivou estudar a ação dos cinco óleos essenciais anteriormente selecionados sobre a qualidade sanitária e fisiológica de sementes de pimentão infectadas por Colletotrichum gloeosporioides. Para o tratamento das sementes, cada óleo essencial foi emulsionado na concentração de 0,25% em solução de água destilada autoclavada + Tween 80. Foram avaliadas a qualidade sanitária das sementes (blotter test) e a qualidade fisiológica (germinação, comprimento de plântulas, emergência de plântulas, índice de velocidade de emergência e massa seca). O óleo essencial de cravo foi o mais eficiente em reduzir a incidência do fungo nas sementes, sem prejudicar a qualidade fisiológica destas. A ocorrência de C. gloeosporioides nas sementes tratadas com os demais óleos essenciais foi alta, tendo o de citronela também interferido negativamente na germinação.
Sweet pepper (Capsicum annum) is one of the most consumed vegetables in the Brazilian market, however, an important fungal disease, anthracnose, can decimate all its fruits in the field. The anthracnose is caused by a complex of species of the genus Colletotrichum, and the fungus can be transmitted by infected seeds, constituting an important means of introducing and disseminating the pathogen in new areas. Then, seed treatment becomes an important measure for anthracnose management and control. Aiming to reduce the application of chemical products in the culture, the research for natural substances with antifungal action has been stimulated. In this work, the action of eight essential oils (rosemary, citronella, clove, copaíba, eucalyptus, mint, basil and tea tree) on Colletotrichum gloeosporioides, isolated from the sweet pepper fruits, was investigated. Initially, the in vitro activity of the essential oils on the fungus was evaluated by adding these oils to the potato-dextrose-agar (PDA) culture medium, in petri dishes, at following concentrations: 0.25%, 0.50% e 0.75%. The fungus was then transferred to the center of each petri dish containing the treatments. The experiment was conducted in a completely randomized design according to the 8x3 factorial scheme (eight essential oils x three concentrations), and one control treatment (composed of pure BDA), and three replicates. The experiment was conducted in duplicate. Plates were maintained at 22°C and 12 hour-photoperiod. To verify the effect of the essential oils, mycelial growth (diameter of colony), percentage of growth inhibition (PIC) and sporulation (number of spores / mL) were evaluated. In both trials, the essential oils of clove, citronella, eucalyptus, mint and basil, regardless of the concentration, totally inhibited the pathogen, not allowing the its sporulation. The second stage of this research aimed to study the action of the five pre-selected essential oils (clove, citronella, eucalyptus, mint and basil) on the sanitary and physiological quality of sweet pepper seeds infected by Colletotrichum gloeosporioides. For the seeds treatment, each essential oil was emulsified at 0.25% concentration in autoclaved water solution + Tween 80. The sanitary (blotter test) and the physiological quality (germination, seedling length, emergence, rate of emergency speed and dry mass). The essential oil of clove showed the best performance in the treatment of seeds, reducing efficiently the incidence of C. gloeosporioides, without harming the physiological quality of the sweet pepper seeds.
Sweet pepper (Capsicum annum) is one of the most consumed vegetables in the Brazilian market, however, an important fungal disease, anthracnose, can decimate all its fruits in the field. The anthracnose is caused by a complex of species of the genus Colletotrichum, and the fungus can be transmitted by infected seeds, constituting an important means of introducing and disseminating the pathogen in new areas. Then, seed treatment becomes an important measure for anthracnose management and control. Aiming to reduce the application of chemical products in the culture, the research for natural substances with antifungal action has been stimulated. In this work, the action of eight essential oils (rosemary, citronella, clove, copaíba, eucalyptus, mint, basil and tea tree) on Colletotrichum gloeosporioides, isolated from the sweet pepper fruits, was investigated. Initially, the in vitro activity of the essential oils on the fungus was evaluated by adding these oils to the potato-dextrose-agar (PDA) culture medium, in petri dishes, at following concentrations: 0.25%, 0.50% e 0.75%. The fungus was then transferred to the center of each petri dish containing the treatments. The experiment was conducted in a completely randomized design according to the 8x3 factorial scheme (eight essential oils x three concentrations), and one control treatment (composed of pure BDA), and three replicates. The experiment was conducted in duplicate. Plates were maintained at 22°C and 12 hour-photoperiod. To verify the effect of the essential oils, mycelial growth (diameter of colony), percentage of growth inhibition (PIC) and sporulation (number of spores / mL) were evaluated. In both trials, the essential oils of clove, citronella, eucalyptus, mint and basil, regardless of the concentration, totally inhibited the pathogen, not allowing the its sporulation. The second stage of this research aimed to study the action of the five pre-selected essential oils (clove, citronella, eucalyptus, mint and basil) on the sanitary and physiological quality of sweet pepper seeds infected by Colletotrichum gloeosporioides. For the seeds treatment, each essential oil was emulsified at 0.25% concentration in autoclaved water solution + Tween 80. The sanitary (blotter test) and the physiological quality (germination, seedling length, emergence, rate of emergency speed and dry mass). The essential oil of clove showed the best performance in the treatment of seeds, reducing efficiently the incidence of C. gloeosporioides, without harming the physiological quality of the sweet pepper seeds.
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Palavras-chave
Antracnose, Atividade antifúngica, Capsicum annum, Substâncias naturais, Anthracnose, Antifungal activity, Natural substances