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Master's Dissertation
DOI
10.11606/D.11.2013.tde-23042013-160451
Document
Author
Full name
Rodrigo José Sorgatto
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Piracicaba, 2013
Supervisor
Committee
Omoto, Celso (President)
Gomez, Daniel Ricardo Sosa
Sato, Mário Eidi
Title in Portuguese
Sobrevivência e desenvolvimento de Spodoptera frugiperda e Pseudoplusia includens (Lepidoptera: Noctuidae) em algodão Cry1Ac/Cry2Ab2 e Cry1Ac/Cry1F: Implicações para o Manejo da Resistência de Insetos
Keywords in Portuguese
Algodão
Lagartas - Resistência
Manejo integrado
Plantas transgênicas
Proteínas de plantas
Abstract in Portuguese
Spodoptera frugiperda (J. E. Smith) e Pseudoplusia includens (Walker) são importantes insetos-praga no algodoeiro (Gossypium hirsutum L.) devido às injúrias de desfolha e destruição de estruturas reprodutivas no caso de S. frugiperda. Os eventos de algodão Bt que expressam as proteínas Cry1Ac/Cry2Ab2 (Bollgard® II) e Cry1Ac/Cry1F (WideStrike(TM)) de Bacillus thuringiensis Berliner são ferramentas disponíveis para o controle dessas espécies-praga. A fim de subsidiar o Manejo da Resistência de Insetos (MRI) foram conduzidos estudos em laboratório para avaliar a sobrevivência e desenvolvimento de S. frugiperda e P. includens nos eventos de algodão Cry1Ac/Cry2Ab2 e Cry1Ac/Cry1F. Em bioensaios com discos de folhas, a eficácia de controle de neonatas nos dois eventos de algodão Bt foi superior a 80% para S. frugiperda e de 100% para P. includens. Em bioensaios com brácteas com neonatas de S. frugiperda, a eficácia de controle de ambos os eventos de algodão Bt também foi superior a 80%. As lagartas de S. frugiperda sobreviventes em algodão Bt apresentaram severa inibição de desenvolvimento larval em folhas (> 75%) e brácteas (> 44%). Em bioensaios com simulações de alimentação larval, as quais consistiam em grupos de lagartas alimentadas com o algodão Bt aos 0, 3, 6, 9, 12, 15 e 18 dias após a inoculação (DAI), S. frugiperda e P. includens demonstraram que a suscetibilidade dessas espécies diminuiu com o avançar do desenvolvimento larval. Para S. frugiperda, em todas as simulações de alimentação com o algodão Cry1Ac/Cry2Ab2 houve lagartas que atingiram as fases de pupa e adulto. Por outro lado, quando expostas ao algodão Cry1Ac/Cry1F, somente algumas das lagartas de 5º e 6º ínstares atingiram as fases de pupa e adulto. Para P. includens, somente lagartas no 6º ínstar atingiram as fases de pupa e adulto quando alimentadas com os dois eventos de algodão Bt. Os parâmetros biológicos de S. frugiperda sobreviventes em algodão Cry1Ac/Cry2Ab2 foram afetados negativamente com aumento da duração da fase larval (? 9 dias), baixa viabilidade larval (1,4%) e de insetos que completaram o ciclo biológico (0,9%), aumento no intervalo entre gerações (? 9 dias) e redução da taxa intrínseca de crescimento populacional (? 83%). Os eventos de algodão Cry1Ac/Cry2Ab2 e Cry1Ac/Cry1F são promissores no controle de S. frugiperda e P. includens. No entanto, a atividade inseticida dos dois eventos de algodão Bt em lagartas de S. frugiperda e P. includens diminui com o desenvolvimento larval e essa constatação deve ser considerada em programas de MRI, especialmente na disposição espacial do refúgio.
Title in English
Survival and development of Spodoptera frugiperda and Pseudoplusia includens (Lepidoptera: Noctuidae) in cotton Cry1Ac/Cry2Ab2 and Cry1Ac/Cry1F: Implications for Insect Resistance Management
Keywords in English
Caterpillars - Resistance
Cotton
Integrated management
Plant proteins
Transgenic plants
Abstract in English
Spodoptera frugiperda (J. E. Smith) and Pseudoplusia includens (Walker) are important insect pests in cotton (Gossypium hirsutum L.) due to damage on leaves and reproductive structures in the case of S. frugiperda. The events of Bt cotton expressing proteins Cry1Ac/Cry2Ab2 (Bollgard® II) and Cry1Ac/Cry1F (WideStrike(TM)) from Bacillus thuringiensis Berliner are tools available to control these pest species. To develop an Insect Resistance Management (IRM), we performed laboratory studies to evaluate the survival and development of S. frugiperda and P. includens. In fresh leaf discs bioassays, the control efficacy of neonates in both Bt cotton events was greater than 80% mortality for S. frugiperda and 100% for P. includens. In fresh bracts bioassays to neonates of S. frugiperda, the control efficacy of both Bt cotton events was over 80%. The surviving larvae of S. frugiperda in Bt cotton showed severe growth inhibition (weight and instar) in leaves (> 75%) and bracts (> 44%). In simulations feed bioassays with larvae, which consisted of groups of larvae fed on Bt cotton at 0, 3, 6, 9, 12, 15 and 18 days after inoculation (DAI), S. frugiperda and P. includens showed that the susceptibility of species decreases with advancing larval development. For S. frugiperda, in all feed simulations with cotton Cry1Ac/Cry2Ab2 had caterpillars that reached pupae and adult stages. Moreover, when exposed to cotton Cry1Ac/Cry1F, only some caterpillars of 5th and 6th instars reached pupae and adult stages. For P. includens, only some caterpillars of 6th instar reached pupae and adult stages when fed with two events of Bt cotton. The biological parameters of S. frugiperda fed on cotton Cry1Ac/Cry2Ab2 were negatively affected with increasing duration of the larval stage (? 9 days), reduced larval viability (1,4%) and insects that completed the life cycle (0,9%), increased the generation time (? 9 days) and decreased the intrinsic rate of increase (? 83%). The events of cotton Cry1Ac/Cry2Ab2 and Cry1Ac/Cry1F are promising for the control of S. frugiperda and P. includens. However, the insecticidal activity of both events of Bt cotton in larvae of S. frugiperda and P. includens decreases through larval development and this finding should be considered in programs of MRI, especially in the spatial arrangement of the refuge.
 
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Publishing Date
2013-05-08
 
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