Manejo de macrophomina phaseolina (tassi) goid. em sementes de feijoeiro (phaseolus vulgaris l.) com óleos essenciais e antagonistas
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Data
2018-01-22
Autores
Santos, Paula Leite dos [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O feijoeiro comum (Phaseolus vulgaris L.) está sujeito à ocorrência de doenças, cujos agentes causais podem ser transportados e transmitidos via sementes, além de comprometer o potencial fisiológico destas. Dentre os patógenos que influenciam negativamente, se presentes nas sementes de feijão, está o fungo Macrophomina phaseolina (Tassi) Goid., que pode ser transmitido às plantas, causando a podridão cinzenta da haste do feijoeiro, uma doença com sérios impactos na cultura. Apesar do tratamento químico de sementes ser uma prática eficiente no controle de patógenos, o emprego de substâncias naturais com ação fungicida e de antagonistas de fitopatógenos surge como uma opção de manejo sustentável. Diante do exposto, o objetivo desta pesquisa foi avaliar o efeito do tratamento de sementes de feijão com óleos essenciais (Capítulo I) e antagonistas (Capítulo II) sobre a incidência do fungo M. phaseolina e o potencial fisiológico das sementes tratadas. No primeiro capítulo, inicialmente, investigou-se a ação in vitro dos óleos essenciais de cravo da índia, pimenta preta e gerânio sobre o crescimento micelial e a esporulação do fungo. Dois tratamentos testemunha foram incluídos: fungicida tiofanato metílico + fluazinam e BDA puro. Verificou-se inibição total do crescimento micelial pelos óleos essenciais de cravo da índia e pimenta preta, com ação semelhante ao fungicida. O óleo essencial de gerânio não apresentou efeito inibitório satisfatório sobre o fungo. Os óleos essenciais de cravo de índia e pimenta preta foram então empregados no tratamento de sementes de feijão, para averiguar seu potencial de controle de M. phaseolina e possíveis efeitos na qualidade fisiológica das sementes tratadas. Os óleos essenciais foram comparados ao fungicida tiofanato metílico + fluazinam, sendo também avaliadas sementes inoculadas sem tratamento e sementes não inoculadas. Os óleos essenciais reduziram a incidência do fungo nas sementes, porém, o óleo essencial de cravo da índia provocou uma redução na germinação destas. Apesar disto, não houve interferência negativa deste óleo sobre o vigor das sementes, avaliado pela primeira contagem de germinação e índice de velocidade de emergência. O óleo essencial de pimenta preta, por sua vez, reduziu a incidência do fungo e não interferiu na germinação e vigor das sementes. O experimento de controle biológico (Capítulo II) também foi constituído inicialmente de uma etapa in vitro, para verificar a possível ação dos antagonistas Bacillus subtilis, B. pumilus e Trichoderma harzianum sobre M. phaseolina. Constatou-se a ação supressora dos antagonistas, com a formação de halo de inibição no teste de confronto em todos os tratamentos. Em seguida, foi realizado o tratamento de sementes com os antagonistas e o fungicida tiofanato metílico + fluazinam, sendo também incluídas no experimento sementes inoculadas e sementes não inoculadas, ambas sem tratamento. Foram avaliados a sanidade e o potencial fisiológico (germinação; primeira contagem de germinação; índice de velocidade de emergência; comprimento de plântulas). Os três antagonistas reduziram a incidência de M. phaseolina nas sementes. Em geral, B. subtilis e T. harzianum mostraram resultados consistentes e satisfatórios, quanto à germinação e primeira contagem de germinação. Não houve diferença entre os tratamentos quanto ao índice de velocidade de emergência e comprimento de plântulas. Pelos resultados obtidos, pode-se concluir que o óleo essencial de pimenta preta e os antagonistas B. subtilis e T. harzianum são alternativas viáveis para o manejo de M. phaseolina em sementes de feijoeiro.
Common bean crop (Phaseolus vulgaris L.) is subject to diseases occurrence, whose causal agents can be transported and transmitted through seeds, besides compromising their physiological potential. Macrophomina phaseolina (Tassi) Goid. is one of the pathogens that negatively influences this potential, if present in common bean seeds. This fungus can be transmitted to the plants, causing charcoal rot of common bean, a disease with serious impacts on this crop. Although the chemical treatment of seeds is an efficient practice in the pathogens control, the use of natural substances with fungicidal action and antagonists of phytopathogens appears as a sustainable management option. This research aimed to evaluate the effect of common bean seeds treatment with essential oils (Chapter I) as well as antagonists (Chapter II) on the incidence of M. phaseolina and the physiological potential of the treated seeds. In the first chapter, the in vitro action of clove, black pepper and geranium essential oils on mycelial growth and fungal sporulation was investigated. Two control treatments were included: methyl thiophanate + fluazinam fungicide and pure potato-dextrose-agar (PDA). Total inhibition of mycelial growth was verified by clove and black pepper essential oils, which showed a fungicide-like action. The geranium essential oil had no satisfactory inhibitory effect on the fungus. Clove and black pepper essential oils were used in the common bean seeds treatment in order to determine their potential for M. phaseolina control and possible effects on the physiological quality of treated seeds. The essential oils treatments were compared with the methyl thiophanate + fluazinam fungicide one. Inoculated and uninoculated seeds were also evaluated. The essential oils reduced the fungus incidence in the seeds, however, clove essential oil caused a germination reduction. In spite of this, there was no negative interference of this oil in seed vigor, evaluated by the first germination count and the emergence speed index. Black pepper essential oil reduced the incidence of the fungus and did not interfere in seeds germination and vigor. The biological control experiment (Chapter II) was also initially comprised an in vitro stage in order to verify the possible action of the antagonists Bacillus subtilis, B. pumilus and Trichoderma harzianum on M. phaseolina. The suppressive action of the antagonists was observed, with an inhibition halo production in the challenge test for all treatments. Then, seed treatment was performed by using antagonists and methyl thiophanate + fluazinam fungicide. Inoculated and uninoculated seeds were also included in the experiment, both without treatment. Seed health and physiological potential (germination, first germination count, emergence speed index and seedlings length) were evaluated. All the antagonists reduced the incidence of M. phaseolina in the seeds. In general, B. subtilis and T. harzianum showed consistent and satisfactory results regarding germination and first germination counting. There was no difference among the treatments for emergence speed index and seedling length. From the results obtained, it can be concluded that black pepper essential oil, B. subtilis and T. harzianum are viable alternatives for M. phaseolina management in common bean seeds.
Common bean crop (Phaseolus vulgaris L.) is subject to diseases occurrence, whose causal agents can be transported and transmitted through seeds, besides compromising their physiological potential. Macrophomina phaseolina (Tassi) Goid. is one of the pathogens that negatively influences this potential, if present in common bean seeds. This fungus can be transmitted to the plants, causing charcoal rot of common bean, a disease with serious impacts on this crop. Although the chemical treatment of seeds is an efficient practice in the pathogens control, the use of natural substances with fungicidal action and antagonists of phytopathogens appears as a sustainable management option. This research aimed to evaluate the effect of common bean seeds treatment with essential oils (Chapter I) as well as antagonists (Chapter II) on the incidence of M. phaseolina and the physiological potential of the treated seeds. In the first chapter, the in vitro action of clove, black pepper and geranium essential oils on mycelial growth and fungal sporulation was investigated. Two control treatments were included: methyl thiophanate + fluazinam fungicide and pure potato-dextrose-agar (PDA). Total inhibition of mycelial growth was verified by clove and black pepper essential oils, which showed a fungicide-like action. The geranium essential oil had no satisfactory inhibitory effect on the fungus. Clove and black pepper essential oils were used in the common bean seeds treatment in order to determine their potential for M. phaseolina control and possible effects on the physiological quality of treated seeds. The essential oils treatments were compared with the methyl thiophanate + fluazinam fungicide one. Inoculated and uninoculated seeds were also evaluated. The essential oils reduced the fungus incidence in the seeds, however, clove essential oil caused a germination reduction. In spite of this, there was no negative interference of this oil in seed vigor, evaluated by the first germination count and the emergence speed index. Black pepper essential oil reduced the incidence of the fungus and did not interfere in seeds germination and vigor. The biological control experiment (Chapter II) was also initially comprised an in vitro stage in order to verify the possible action of the antagonists Bacillus subtilis, B. pumilus and Trichoderma harzianum on M. phaseolina. The suppressive action of the antagonists was observed, with an inhibition halo production in the challenge test for all treatments. Then, seed treatment was performed by using antagonists and methyl thiophanate + fluazinam fungicide. Inoculated and uninoculated seeds were also included in the experiment, both without treatment. Seed health and physiological potential (germination, first germination count, emergence speed index and seedlings length) were evaluated. All the antagonists reduced the incidence of M. phaseolina in the seeds. In general, B. subtilis and T. harzianum showed consistent and satisfactory results regarding germination and first germination counting. There was no difference among the treatments for emergence speed index and seedling length. From the results obtained, it can be concluded that black pepper essential oil, B. subtilis and T. harzianum are viable alternatives for M. phaseolina management in common bean seeds.
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Palavras-chave
Podridão cinzenta da haste do feijoeiro, Patologia de sementes, Controle alternativo, Controle biológico, Charcoal rot of common bean, Seed pathology, Alternative control, Biological control