Caracterização da resistência de Rachiplusia nu (Guenée, 1852) (Lepidoptera: Noctuidae) a proteína inseticida Cry1Ac expressa em soja

• Ano de defesa: 2024
• Autor(a) principal: Reis, Alexandre Castro
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• dARK ID: ark:/26339/001300001b5xt
• Idioma: por
• Instituição de defesa: Universidade Federal de Santa Maria; Brasil; Produção Vegetal; UFSM; Programa de Pós-Graduação em Agronomia; Centro de Ciências Rurais
• Palavras-chave em Português: Falsa-medideira; Soja Bt; Padrão de herança; Manejo da resistência; Sunflower looper; Bt soybean; Inheritance pattern; Resistance management; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA
• Link de acesso: http://repositorio.ufsm.br/handle/1/33105

Rachiplusia nu (Guenée, 1852) (Lepidoptera: Noctuidae) was historically a secondary soybean pest in Brazil. From 2021 onwards, unexpected damage of R. nu has been detected in soybean fields expressing the Cry1Ac insecticidal protein from Bacillus thuringiensis (Berliner, 1911) in Brazil and Argentina. On this basis, the goal of this study was to select resistant and susceptible strains of R. nu to Cry1Ac expressed in soybean. After selection, studies were carried out to evaluate the survival of resistant and susceptible strains in Cry1Ac soybean leaves and non-Bt soybean. Then, the inheritance of resistance, cross-resistance of Cry1Ac with Cry1A.105 and Cry2Ab2 and fitness cost of resistance to Cry1Ac in R. nu was characterized. To characterize the inheritance of resistance, diet-overlay bioassays was carried out to estimate the lethal concentrations of Cry1Ac against resistant, susceptible and F1 progeny of reciprocal crosses (heterozygotes). To evaluate cross-resistance, resistant and susceptible strains to Cry1Ac were exposed to Cry1A.105 and Cry2Ab2 in diet-overlay bioassays. The fitness cost of resistance was estimated by comparing the biological parameters of resistant, susceptible and heterozygous strains when they developed on non-Bt soybean leaves. Neonates of the Cry1Ac-resistant strain of R. nu were able to develop on Cry1Ac soybean leaves and emerge as fertile adults, while neonates from the susceptible and heterozygotes strains did not survive beyond 10 d. The resistance ratio to Cry1Ac estimated in diet-overlay bioassays in the resistant strain was >736.92-fold. The inheritance pattern of Cry1Ac resistance in R. nu was characterized as autosomal recessive and monogenic. The Cry1Ac-resistant strain of R. nu also exhibited high resistance to Cry1A.105 (resistance ratio >159.87-fold), but negligible resistance to Cry2Ab2 (resistance ratio = 1.25-fold). Life history data showed that the resistance to Cry1Ac in R. nu is not linked with a substantial fitness cost. The inheritance pattern of Cry1Ac resistance in R. nu is autosomal recessive, monogenic and not associated with obvious fitness costs. Cross-resistance occurred between Cry1Ac and Cry1A.105 in R. nu but no cross-resistance to Cry2Ab2, indicating that the Cry1A.105/Cry2Ab2/Cry1Ac soybean is a valuable and effective tool to manage Cry1Ac resistance in R. nu. This is the first study reporting the genetic basis of Cry1Ac resistance in R. nu.