Dinâmica populacional, infestação natural e aspectos biológicos de Chrysodeixis includens (Walker: 1857) e Spodoptera spp. (Lepidoptera: Noctuidae) em cultivares de soja e algodoeiro Bt que expressam proteínas Cry
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Data
2018-02-16
Autores
Viana, Daniela de Lima [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O cenário agrícola no Centro Oeste conta com os chamados sistemas de produção, nos quais os cultivos ocorrem de forma constante e sucessiva durante um mesmo ano agrícola. No entanto, isso tem propiciado problemas cada vez mais frequentes relacionados a alguns grupos de pragas, dentre eles os lepidópteros. Espécies como Chrysodeixis includens e o complexo de Spodoptera vem crescendo de importância, causando prejuízos, principalmente em culturas como a soja e o algodoeiro. Dentre os métodos mais utilizados para o controle de insetos-praga no Brasil, destaca-se o uso de OGM, a partir da inserção de genes da bactéria Bacillus thuringiensis (Bt), com expressão de proteínas com ações inseticidas. Entretanto, um dos grandes problemas é a seleção de populações de pragas resistentes aos cultivos Bt devido ao uso contínuo e inadequado da tecnologia. Diante disso, os objetivos do presente estudo foram avaliar os efeitos de cultivares Bt de soja e algodoeiro, que expressam proteínas inseticidas Cry, sobre os aspectos biológicos de C. includens em laboratório, como também avaliar a dinâmica populacional e a infestação natural de lagartas de C. includens e de Spodoptera spp. em condições de campo, no estado do Mato Grosso. Para o estudo dos aspectos biológicos, utilizou-se lagartas neonatas que foram alimentadas com folhas das cultivares de soja e algodoeiro não Bt e Bt de diferentes tecnologias. Os experimentos de campo foram realizados em área experimental do IMAmt na safra 2016/2017, utilizando cultivares de soja e algodoeiro não Bt e Bt com expressão de diferentes proteínas Cry. As cultivares de soja Bt, que expressam a proteína Cry1Ac, afetam os parâmetros biológicos de C. includens, controlando de maneira eficiente, tanto em laboratório quanto em campo. Em relação às lagartas de Spodoptera spp. observou-se que as cultivares de soja Bt não controlam eficientemente esses lepidópteros. A cultivar de algodoeiro que expressa a proteína Cry1Ac, causa pouco efeito sobre as lagartas de C. includens, não apresentando controle satisfatório, tanto nos aspectos biológicos observados em laboratório quanto na infestação em campo, se comportando de forma similar à cultivar de algodoeiro não Bt. As cultivares de algodoeiro Bt piramidadas, Cry1Ac+Cry1F, Cry1Ac+Cry2Ab2 e Cry1Ab+Cry2Ae, apresentaram controle de C. includens, afetando a sobrevivência de lagartas pequenas em laboratório e campo. Por outro lado, a piramidação de cultivares por si só não é suficiente, por exemplo, para as lagartas de Spodoptera spp. Nos eventos de algodão Bt em campo, verificou-se que as cultivares que expressam as proteínas Cry1Ac e Cry1Ac+Cry1F, não suprimem suas infestações, enquanto que nas cultivares piramidadas que expressam Cry1Ac+Cry2Ab2 e Cry1Ab+Cry2Ae a supressão foi considerada eficiente.
The agricultural scenario in the brazilian midwest counts on the socalled production systems, in which crops occur constantly and successively during the same agricultural year. However, this has caused increasingly frequent problems related to some groups of pests, among them the Lepidoptera. Species such as Chrysodeixis includens and the Spodoptera complex have been increasing in importance, causing damage, especially in crops such as soybean and cotton. Among the most used methods for the control of insect pests in Brazil, the use of GMOs, from the insertion of genes of the bacterium Bacillus thuringiensis (Bt), with expression of proteins with insecticidal actions, stands out. However, one of the major problems is the selection of populations of pests resistant to Bt crops due to the continuous and inadequate use of the technology. The objectives of the present study were to evaluate the effects of Bt cultivars of soybean and cotton, which express insecticidal Cry proteins, on the biological aspects of C. includens in the laboratory, as well as to evaluate the population dynamics and the natural infestation of caterpillars C. includens and Spodoptera spp. under field conditions, in the state of Mato Grosso. For the study of the biological aspects, we used caterpillars that were fed with leaves of the cultivars of soybean and non-Bt and Bt cotton of different technologies. Field experiments were carried out in the experimental area of the IMAmt in the 2016/2017 season, using soybean and cotton cultivars non-Bt and Bt with different Cry protein expression. Soybean Bt cultivars, which express the Cry1Ac protein, affect the biological parameters of C. includens, efficiently controlling both in the laboratory and in the field. In relation to the caterpillars of Spodoptera spp., it was observed that Bt soybean cultivars do not efficiently control these lepidoptera. The cotton cultivar that expresses the Cry1Ac protein causes little effect on the caterpillars of C. includens, not showing satisfactory control, both in the biological aspects observed in the laboratory and in the infestation in the field, behaving in a similar way to the cultivar of non-Bt cotton. Cotton Bt cultivars, Cry1Ac+Cry1F, Cry1Ac+Cry2Ab2 and Cry1Ab+Cry2Ae, showed control of C. includens, affecting the survival of small caterpillars in the laboratory and in the field. On the other hand, the pyramiding of cultivars alone is not sufficient, for example, for the caterpillars of Spodoptera spp. In the field cotton Bt events, it was found that cultivars expressing the Cry1Ac and Cry1Ac+Cry1F proteins do not suppress their infestations, whereas in pyrite cultivars expressing Cry1Ac+Cry2Ab2 and Cry1Ab+Cry2Ae suppression was considered efficient.
The agricultural scenario in the brazilian midwest counts on the socalled production systems, in which crops occur constantly and successively during the same agricultural year. However, this has caused increasingly frequent problems related to some groups of pests, among them the Lepidoptera. Species such as Chrysodeixis includens and the Spodoptera complex have been increasing in importance, causing damage, especially in crops such as soybean and cotton. Among the most used methods for the control of insect pests in Brazil, the use of GMOs, from the insertion of genes of the bacterium Bacillus thuringiensis (Bt), with expression of proteins with insecticidal actions, stands out. However, one of the major problems is the selection of populations of pests resistant to Bt crops due to the continuous and inadequate use of the technology. The objectives of the present study were to evaluate the effects of Bt cultivars of soybean and cotton, which express insecticidal Cry proteins, on the biological aspects of C. includens in the laboratory, as well as to evaluate the population dynamics and the natural infestation of caterpillars C. includens and Spodoptera spp. under field conditions, in the state of Mato Grosso. For the study of the biological aspects, we used caterpillars that were fed with leaves of the cultivars of soybean and non-Bt and Bt cotton of different technologies. Field experiments were carried out in the experimental area of the IMAmt in the 2016/2017 season, using soybean and cotton cultivars non-Bt and Bt with different Cry protein expression. Soybean Bt cultivars, which express the Cry1Ac protein, affect the biological parameters of C. includens, efficiently controlling both in the laboratory and in the field. In relation to the caterpillars of Spodoptera spp., it was observed that Bt soybean cultivars do not efficiently control these lepidoptera. The cotton cultivar that expresses the Cry1Ac protein causes little effect on the caterpillars of C. includens, not showing satisfactory control, both in the biological aspects observed in the laboratory and in the infestation in the field, behaving in a similar way to the cultivar of non-Bt cotton. Cotton Bt cultivars, Cry1Ac+Cry1F, Cry1Ac+Cry2Ab2 and Cry1Ab+Cry2Ae, showed control of C. includens, affecting the survival of small caterpillars in the laboratory and in the field. On the other hand, the pyramiding of cultivars alone is not sufficient, for example, for the caterpillars of Spodoptera spp. In the field cotton Bt events, it was found that cultivars expressing the Cry1Ac and Cry1Ac+Cry1F proteins do not suppress their infestations, whereas in pyrite cultivars expressing Cry1Ac+Cry2Ab2 and Cry1Ab+Cry2Ae suppression was considered efficient.
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Palavras-chave
Bacillus thuringiensis, Cry1Ac, Falsa-medideira, Proteínas piramidadas, Transgênicos, Soybean looper, Pyramidal proteins, Transgenic