Controle biológico de Colletotrichum acutatum, agente causal da queda prematura dos frutos cítricos
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Data
2003-06-01
Autores
Kupper, Katia C. [UNESP]
Gimenes-Fernandes, Nelson [UNESP]
Goes, Antonio de [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Sociedade Brasileira de Fitopatologia
Resumo
O trabalho teve por finalidade estudar a potencialidade antagonística de isolados de Bacillus subtilis a Colletotrichum acutatum, agente causal da queda prematura dos frutos cítricos (Citrus spp.) (QPFC), sob condições de laboratório e de campo. Foram estudados 64 isolados de B. subtilis, quatro isolados de Bacillus spp. e um isolado de B. thuringiensis quanto à capacidade de inibir o desenvolvimento do patógeno em cultura pareada e quanto à produção de metabólitos com atividade antimicrobiana. Os isolados mais promissores foram testados em condições de campo para controle da doença. In vitro, todos os isolados de Bacillus spp. inibiram o crescimento de C. acutatum, não havendo diferenças significativas entre eles. Os isolados de Bacillus spp. produziram, in vitro, metabólitos capazes de inibir o crescimento micelial de C. acutatum, os quais mantiveram suas atividades capazes de causar a inibição, após autoclavagem a 120 ºC, durante 20 min. Dentre os sete isolados de B. subtilis testados para o controle da QPFC, em condições naturais, o ACB-69 diferiu da testemunha e de vários outros isolados, porém equiparou-se estatisticamente ao benomyl, proporcionando menor porcentagem de flores com sintomas e maior número médio de frutos efetivos. Ainda, sob condições de campo, isolados de cada uma das espécies Trichoderma viride, T. pseudokoningii e T. aureoviride foram ineficientes, apresentando o mesmo comportamento da testemunha. em relação aos métodos de avaliação da doença, a porcentagem de flores com sintomas foi mais eficiente do que o número médio de frutos efetivos (NMFE), uma vez que esses resultam do efeito direto do patógeno.
The present study evaluated the antagonistic potential of different isolates of Bacillus subtilis to Colletotrichum acutatum, causal agent of post-bloom fruit drop of citrus (Citrus spp.) (PFD), under laboratory and field conditions. Sixty four isolates of B. subtilis, four isolates of Bacillus spp. and one isolate of B. thuringiensis were evaluated in relation to their ability to inhibit the development of the plant pathogen in paired cultures and their production of metabolites with antimicrobial activity. The most promising isolates were tested for the control of the disease under field conditions. All the Bacillus spp. isolates induced strong inhibition on the growth of the plant pathogen. The isolates of Bacillus spp. produced, in vitro, metabolites capable of inhibiting the mycelial growth of C. acutatum, and they maintained their activities in enough concentrations to cause the inhibition, even after submitted to 120 ºC, for 20 min. The inhibition of C. acutatum by B. subtilis was due to antibiosis. Among seven isolates of B. subtilis tested for the disease control, in natural conditions, the BCA-69 differed from the control, and was statistically similar to benomyl, presenting lower percentage of symptomatic flowers and higher average number of effective fruits. An isolate of each of the species of Trichoderma viride, T. pseudokoningii and T. aureovirde were also tested, in field conditions, for controlling PFD, and none differed from the control. The percentage of symptomatic flowers was more efficient than the average number of effective fruits (ANEF) in determining the effect of the applications of the biocontrol agents on disease control.
The present study evaluated the antagonistic potential of different isolates of Bacillus subtilis to Colletotrichum acutatum, causal agent of post-bloom fruit drop of citrus (Citrus spp.) (PFD), under laboratory and field conditions. Sixty four isolates of B. subtilis, four isolates of Bacillus spp. and one isolate of B. thuringiensis were evaluated in relation to their ability to inhibit the development of the plant pathogen in paired cultures and their production of metabolites with antimicrobial activity. The most promising isolates were tested for the control of the disease under field conditions. All the Bacillus spp. isolates induced strong inhibition on the growth of the plant pathogen. The isolates of Bacillus spp. produced, in vitro, metabolites capable of inhibiting the mycelial growth of C. acutatum, and they maintained their activities in enough concentrations to cause the inhibition, even after submitted to 120 ºC, for 20 min. The inhibition of C. acutatum by B. subtilis was due to antibiosis. Among seven isolates of B. subtilis tested for the disease control, in natural conditions, the BCA-69 differed from the control, and was statistically similar to benomyl, presenting lower percentage of symptomatic flowers and higher average number of effective fruits. An isolate of each of the species of Trichoderma viride, T. pseudokoningii and T. aureovirde were also tested, in field conditions, for controlling PFD, and none differed from the control. The percentage of symptomatic flowers was more efficient than the average number of effective fruits (ANEF) in determining the effect of the applications of the biocontrol agents on disease control.
Descrição
Palavras-chave
Citrus sinensis, Controle biológico, substâncias antifúngicas
Como citar
Fitopatologia Brasileira. Sociedade Brasileira de Fitopatologia, v. 28, n. 3, p. 251-257, 2003.