Seleção e caracterização de isolados de Bacillus thuringiensis para o controle de Thyrinteina arnobia (Stoll, 1782) (Lepdoptera: Geometridae)
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Data
2012-11-05
Autores
Horta, André Ballerini [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Bioinseticidas a base de Bacillus thuringiensis são utilizados há décadas no controle de Thyrinteina arnobia (Stoll, 1782) (Lepidoptera: Geometridae) em plantios de eucalipto no Brasil. No entanto, não há relatos de quais genes cry são eficientes para o controle desta praga. Neste sentido, 74 isolados de B. thuringiensis foram caracterizados por PCR para a detecção dos genes cry1, cry1Ab e cry1Ac e sua eficiência no controle de T. arnobia verificada por bioensaios. Os isolados Br9, Br69 Br74, Br81 e R26 apresentaram elevada mortalidade e sua CL50 foi determinada. Os genes cry1Ab e cry1Ac ocorreram isoladamente em 16% e 45% dos isolados, respectivamente, quando presentes em conjunto o controle das lagartas foi superior a 50%, e os valores de CL50 foram os mais elevados. Ambos os genes ocorreram em 11% dos isolados, os níveis de controle foram superiores a 80% e a CL50 era mais baixa, o que sugere que sua presença em conjunto confere maior toxicidade. É evidente que mais estudos em relação à detecção dos genes presentes em isolados de B. thuringiensis e sua contribuição no controle para T. arnobia são fundamentais para esclarecer quais genes conferem maior toxicidade e como eles atuam isoladamente ou em conjunto no controle dessas lagartas, visando a construção de plantas geneticamente modificadas, formulação de bioinseticidas ou desenvolvimento de programas de manejo de resistência destes insetos para a cultura do eucalipto no Brasil
Biopesticides based on Bacillus thuringiensis have been used for decades to control Thyrinteina arnobia (Stoll, 1782) (Lepidoptera: Geometridae) in eucalyptus plantations in Brazil. However, there are no reports of which cry genes are efficient to control this insect pest. In this study, 74 strains of B. thuringiensis were characterized by PCR for detection of cry1, cry1Ab and cry1Ac genes and its efficiency in controlling T. arnobia was verified by bioassays. The strains Br9, Br69, Br74, Br81 and R26 showed the highest mortality rates and their LC50 was determined. The cry1Ab and cry1Ac genes occurred separately in 16% and 45% of the isolates, respectively, and when present together the larvae control was above 50%, and the LC50 values were the highest. Both genes occured in 11% of the isolates, the control levels exceeded 80% and the LC50 was lower, suggesting that their presence together confers higher toxicity. It became evident that further studies regarding the detection of the genes present in isolates of B. thuringiensis, and its contribution to control T. arnobia are essential to clarify which genes confer higher toxicity and how they act individually or together to control these caterpillars, aiming the construction of genetically modified plants, biopesticides formulation or development of more effective resistance management programs for these insects for the cultivation of eucalyptus in Brazil
Biopesticides based on Bacillus thuringiensis have been used for decades to control Thyrinteina arnobia (Stoll, 1782) (Lepidoptera: Geometridae) in eucalyptus plantations in Brazil. However, there are no reports of which cry genes are efficient to control this insect pest. In this study, 74 strains of B. thuringiensis were characterized by PCR for detection of cry1, cry1Ab and cry1Ac genes and its efficiency in controlling T. arnobia was verified by bioassays. The strains Br9, Br69, Br74, Br81 and R26 showed the highest mortality rates and their LC50 was determined. The cry1Ab and cry1Ac genes occurred separately in 16% and 45% of the isolates, respectively, and when present together the larvae control was above 50%, and the LC50 values were the highest. Both genes occured in 11% of the isolates, the control levels exceeded 80% and the LC50 was lower, suggesting that their presence together confers higher toxicity. It became evident that further studies regarding the detection of the genes present in isolates of B. thuringiensis, and its contribution to control T. arnobia are essential to clarify which genes confer higher toxicity and how they act individually or together to control these caterpillars, aiming the construction of genetically modified plants, biopesticides formulation or development of more effective resistance management programs for these insects for the cultivation of eucalyptus in Brazil
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Palavras-chave
Eucalipto - Doenças e pragas - Controle biológico, Lagarta, Lepidoptero, Bactérias gram-positivas, Proteinas de bacterias, Agricultural pests - Biological control
Como citar
HORTA, André Ballerini. Seleção e caracterização de isolados de Bacillus thuringiensis para o controle de Thyrinteina arnobia (Stoll, 1782) (Lepdoptera: Geometridae). 2012. iii, 30 p. Dissertação (mestrado) - Universidade Estadual Paulista, Faculdade de Ciências Agrárias e Veterinárias, 2012.