Nematoides entomopatogênicos para o controle de nematoide-das-galhas Meloidogyne enterolobii
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Data
2019-03-28
Autores
Damascena, Alixelhe Pacheco
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Universidade Estadual Paulista (Unesp)
Resumo
Nos últimos anos, tem-se estudado o uso de nematóides entomopatogênicos (NEPs) como estratégia de controle de nematoides parasitas de plantas. No entanto, são necessários estudos que comprovem em quais fases do desenvolvimento dos nematoides fitoparasitas ocorre o efeito dos NEPs e os mecanismos envolvidos. Para verificar a influência Steinernema brazilense IBCB 06, S. feltiae (Filipjev) IBCB 47, S. rarum (Doucet) IB (Rhabditida: Steinernematidae), Heterorhabditis amazonensis IBCB 24 e H. bacteriophora (Poinar) IB (Rhabditida: Heterorhabditidae) na eclosão do fitonematoide M. enterolobii, 500 ovos e 1.000 juvenis infectantes de cada espécie de nematoide entomopatogênico foram colocados em um recipiente de plástico totalizando 25 mL de suspensão e mantidos em câmara incubadora a 25ºC. O número de juvenis eclodido na suspensão foi contado a cada dois dias totalizando 10 dias. Para contagem, foi retirado um mL de suspensão e o nematoide contado na câmara de Peters sob microscópio de luz. Para avaliar o efeito dos NEPs sobre a mortalidade de juvenis infectantes de M. enterolobii, 500 juvenis infectantes de e 1.000 juvenis de cada espécie de nematoide entomopatogênico foram colocados em um recipiente de plástico totalizando 25 mL de suspensão. A mortalidade foi avaliada a cada dois dias por um tempo de 10 dias. A avaliação da mortalidade de M. enterolobii foi realizada pela contagem dos nematoides móveis e imóveis adicionando-se duas gotas de NaOH 1N à suspensão de nematoides. A contagem foi feita logo a seguir, considerando-se mortos os nematoides retos e imóveis, e, vivos, os retorcidos. Os experimentos foram conduzidos em delineamento experimental inteiramente casualizados, em esquema de parcelas subdivididas no tempo, com seis repetições. Os dados foram submetidos à análise de variância, comparando-se as médias pelo teste Scott-Knott a 5% de probabilidade no programa R Development Core Team. Para avaliar o efeito dos NEPs sobre a infecção por M. enterolobii, mudas de tomateiro foram inoculadas com 500 ovos e juvenis infectantes de M. enterolobii e 0 (somente água), 100, 500, 1.000 e 5.000 juvenis de NEPs por vaso. Sessenta dias após a inoculação, o sistema radicular de cada planta foi lavado em água corrente e submetido à coloração com Floxina B para a obtenção dos índices de galhas (IG) e índices de massas de ovos (IMO). Além disso, o sistema radicular foi pesado e cortado em pedaços pequenos para extração dos ovos. O número total de ovos e juvenis de M. enterolobii por sistema radicular foi quantificado com o auxílio de um microscópio de luz e lâminas de Peters e posteriormente calculado o fator de reprodução. Os experimentos foram conduzidos em delineamento experimental inteiramente casualizados, em esquema de fatorial duplo, com seis repetições. Os dados foram submetidos à análise de variância, comparando-se as médias pelo teste de Tukey a 5% de probabilidade no programa R Development Core Team. Os resultados demonstraram que a utilização dos nematoides entomopatogênicos testados S. brazilense, S. feltiae, S. rarum, H. amazonensis e H. bacteriophora afetam a eclosão de M. enterolobii, proporcionando menor número de juvenis eclodidos. De forma geral os NEPs S. brazilense e S. rarum proporcionaram mortalidade no segundo dia após a instalação do experimento e H. bacteriophora afetou a mortalidade dos juvenis no 4º dia. Nas demais avaliações, não houve diferença estatística. Além disso, todos os NEPs proporcionaram redução do número de galhas, massa de ovos, número total de nematoides e fator de reprodução na concentração de 5.000 juvenis por vaso. Entretanto, S. feltiae em baixas concentrações (100 juvenis por vaso) se destaca por proporcionar redução nos mesmos parâmetros metodológicos avaliados. Os resultados obtidos demonstram o potencial da utilização de NEPs em programas de manejo integrado de M. enterolobii.
In recent years, the use of entomopathogenic nematodes (EPNs) has been studied as a strategy to control plant parasitic nematodes. However, studies are needed to prove in which phases of development of plant-parasitic-nematodes occurs the effect of EPNs and the mechanisms involved. To verify the influence of Steinernema brazilense IBCB 06, S. feltiae (Filipjev) IBCB 47, S. rarum (Doucet) IB (Rhabditida: Steinernematidae), Heterorhabditis amazonensis IBCB 24 e H. bacteriophora (Poinar) IB (Rhabditida: Heterorhabditidae) in the hatching of M. enterolobii, 500 eggs and 1.000 infective juveniles of each entomopathogenic nematode species were placed in a plastic container totaling 25 ml of suspension and kept in an incubator chamber at 25 °C. The number of juveniles hatched in the suspension was counted every two days totaling 10 days. For counting, one mL of suspension was withdrawn and the nematode counted in a Peters's chamber under light microscope. To evaluate the effect of EPNs on the mortality of M. enterolobii infective juveniles, 500 juvenile infective of 1000 juveniles of each entomopathogenic nematode species were placed in a plastic container totaling 25 mL of suspension. Mortality was assessed every two days for a time of 10 days. The evaluation of M. enterolobii mortality was performed by counting the mobile and immobile nematodes by adding two drops of 1N NaOH to the nematode suspension followed by counting, considering the dead straight and immobile nematodes, and, alive, the twisted ones. The experiments were conducted in a completely randomized experimental design, in a subdivided plots scheme with six replications. The data were submitted to analysis of variance, comparing the means by the Scott-Knott test to 5% probability in the R Development Core Team program.To evaluate the effect of EPNs on M. enterolobii infection, tomato seedlings were inoculated with 500 eggs and infective juveniles of M. enterolobii and 0 (water only), 100, 500, 1,000 and 5,000 juveniles of EPNs per pot. Sixty days after inoculation, the root system of each plant was washed in running water and subjected to floxin B staining to obtain gall indexes (GI) and egg mass indexes (IMO). In addition, the root system was weighed and cut into small pieces for egg extraction. The total number of eggs and juveniles of M. enterolobii by root system was quantified with the aid of a light microscope and Peters' slides and then the reproduction factor was calculated. The experiments were conducted in a completely randomized experimental design with a double factorial scheme with six replications. The data were submitted to analysis of variance, comparing the means by the Tukey test at 5% probability in the R Development Core Team program. The results showed that the use of the entomopathogenic nematodes tested S. brazilense, S. feltiae, S. rarum, H. amazonensis and H. bacteriophora affect the hatching of M. enterolobii, providing a smaller number of juvenile hatchlings. In general, EPNs S. brazilense and S. rarum provided mortality on the second day after the experiment, and H. bacteriophora affected juvenile mortality on the 4th day. In the other evaluations, there was no statistical difference. In addition, all EPNs reduced the number of galls, egg mass, total number of nematodes and reproduction factor at the concentration of 5.000 juveniles per pot. However, S. feltiae at low concentrations (100 juveniles per vessel) is notable for providing reduction in the same methodological parameters evaluated. The results demonstrate the potential of the use of EPNs in integrated management programs of M. enterolobii.
In recent years, the use of entomopathogenic nematodes (EPNs) has been studied as a strategy to control plant parasitic nematodes. However, studies are needed to prove in which phases of development of plant-parasitic-nematodes occurs the effect of EPNs and the mechanisms involved. To verify the influence of Steinernema brazilense IBCB 06, S. feltiae (Filipjev) IBCB 47, S. rarum (Doucet) IB (Rhabditida: Steinernematidae), Heterorhabditis amazonensis IBCB 24 e H. bacteriophora (Poinar) IB (Rhabditida: Heterorhabditidae) in the hatching of M. enterolobii, 500 eggs and 1.000 infective juveniles of each entomopathogenic nematode species were placed in a plastic container totaling 25 ml of suspension and kept in an incubator chamber at 25 °C. The number of juveniles hatched in the suspension was counted every two days totaling 10 days. For counting, one mL of suspension was withdrawn and the nematode counted in a Peters's chamber under light microscope. To evaluate the effect of EPNs on the mortality of M. enterolobii infective juveniles, 500 juvenile infective of 1000 juveniles of each entomopathogenic nematode species were placed in a plastic container totaling 25 mL of suspension. Mortality was assessed every two days for a time of 10 days. The evaluation of M. enterolobii mortality was performed by counting the mobile and immobile nematodes by adding two drops of 1N NaOH to the nematode suspension followed by counting, considering the dead straight and immobile nematodes, and, alive, the twisted ones. The experiments were conducted in a completely randomized experimental design, in a subdivided plots scheme with six replications. The data were submitted to analysis of variance, comparing the means by the Scott-Knott test to 5% probability in the R Development Core Team program.To evaluate the effect of EPNs on M. enterolobii infection, tomato seedlings were inoculated with 500 eggs and infective juveniles of M. enterolobii and 0 (water only), 100, 500, 1,000 and 5,000 juveniles of EPNs per pot. Sixty days after inoculation, the root system of each plant was washed in running water and subjected to floxin B staining to obtain gall indexes (GI) and egg mass indexes (IMO). In addition, the root system was weighed and cut into small pieces for egg extraction. The total number of eggs and juveniles of M. enterolobii by root system was quantified with the aid of a light microscope and Peters' slides and then the reproduction factor was calculated. The experiments were conducted in a completely randomized experimental design with a double factorial scheme with six replications. The data were submitted to analysis of variance, comparing the means by the Tukey test at 5% probability in the R Development Core Team program. The results showed that the use of the entomopathogenic nematodes tested S. brazilense, S. feltiae, S. rarum, H. amazonensis and H. bacteriophora affect the hatching of M. enterolobii, providing a smaller number of juvenile hatchlings. In general, EPNs S. brazilense and S. rarum provided mortality on the second day after the experiment, and H. bacteriophora affected juvenile mortality on the 4th day. In the other evaluations, there was no statistical difference. In addition, all EPNs reduced the number of galls, egg mass, total number of nematodes and reproduction factor at the concentration of 5.000 juveniles per pot. However, S. feltiae at low concentrations (100 juveniles per vessel) is notable for providing reduction in the same methodological parameters evaluated. The results demonstrate the potential of the use of EPNs in integrated management programs of M. enterolobii.
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Palavras-chave
Eclosão, Mortalidade, Infecção, Controle Biológico, Hatching, Mortality, Infection, Biological control