Seleção e caracterização de estirpes de Bacillus thuringiensis tóxicas à spodoptera eridania (Cramer), Spodoptera cosmioides (Walker) e Spodoptera frugiperda (smith) (Lepidoptera: noctuidae)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Among the pests of cultivated plants the species of the gender Spodoptera is one of the most important. Spodoptera cosmioides and Spodoptera eridania were reported as cotton (Gossypium hirsutum) and soybean pests (Glycine max), while Spodoptera frugiperda corn (Zea mays) and cotton pests. The objectives of this research were select strains of Bacillus thuringiensis could be effective against S. cosmioides, S. eridania and different geographical populations of S. frugiperda, besides identifying proteins Cry for the control of those species. The intention of this work also was characterized by morphologic and molecular methods, strains that can be used in the biological control of S. cosmioides, S. eridania and S. frugiperda through a formulation. One hundred strains that presented toxicity to insects of the order Lepidoptera had been tested against larvae of three species of Spodoptera through selective bioassay. Dose Bioassay was accomplished with strains of B. thuringiensis that caused mortality above 70% in the selective bioassay. The CL50 of S. eridania, S. cosmioides and populations of S. frugiperda of the states of Bahia and Paraná were determinated by strains of B. thuringiensis. After the molecular characterization, the proteins Cry, identified and common among the strains, were purified for the accomplishment of the dose bioassay against the three species. The strains that demonstrated are promising in the control of the three species Spodoptera were formulated. For the dose bioassay and evaluation of the formulated preliminaries, the concentrations were prepared and inoculated in artificial diet. The mortality evaluation of the caterpillars was accomplished in the second and fifth day after the dose bioassay and the formulation test. The strains S608, BR9, BR10, BR37 and BR45 showed high mortality to the larvae of S. eridania, S. cosmioides and S. frugiperda, were identified, through PCR, the genes cry1Aa, cry1Ab, cry1Ac, cry1B and cry2; cry1Aa, cry1Ab, cry1Ac, cry1B, cry2; cry1Aa, cry1Ab, cry1Ac, cry1B, cry3; cry1Aa, cry1Ab, cry1Ad, cry1C, cry1D, cry1E, cry2 and cry1Aa, cry1Ab, cry1Ac, cry1B, cry3 in DNA of the strains S608, BR9, BR10, BR37 and BR45 respectively. S. eridania and S. cosmioides were more susceptibility the protein Cry2A and Cry1Ab respectively, S. frugiperda presented high mortality to the proteins Cry1Aa and Cry1Ab. The formulations caused 100% mortality. The identification of strains of B. thuringiensis with high level of insecticidal activity of three species Spodoptera offers new perspectives of control.

ASSUNTO(S)

bacillus thuringiensis espodopteros microorganismos fitopatogênicos bacillus thurigiensis phytopathogenic micro-organisms

ACESSO AO ARTIGO

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