Rapid selection and characterization of Cry1F resistance in a Brazilian strain of fall armyworm

Abstract

Transgenic maize (Zea mays L., Poaceae) event TC1507, producing the Cry1F protein of Bacillus thuringiensis Berliner, has been used for management of the fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), in Brazil since 2009. A strain of S. frugiperda, obtained from field collections of larvae in TC1507 maize in Minas Gerais state in 2010, was selected in the laboratory for resistance to Cry1F using leaves of TC1507 maize in two selection regimes. Continuous exposure of larvae to Cry1F was more effective than exposure for 6, 8, and 10 days in the selection of resistant S. frugiperda individuals. With only four generations of laboratory selection, a strain with high levels of resistance to Cry1F was obtained, as indicated by the survival of insects reared on leaves of TC1507 maize plants and by the more than 300‐fold resistance level measured in bioassays with the purified Cry1F protein. Importantly, reciprocal crosses between control and the Cry1F‐selected strains revealed that the resistance is autosomal and incompletely recessive, and the response obtained in the backcross of the F1 generation with the resistant strain was consistent with simple monogenic inheritance. Additionally, there were no apparent fitness costs associated with resistance either for survival or larval growth on non‐Bt maize leaves. Our findings provide experimental evidence for rapid evolution of Cry1F resistance in S. frugiperda in the laboratory and further reinforce the potential of this species to evolve field resistance to the TC1507 maize as previously reported. The resistant strain isolated in this study provides an opportunity to estimate the resistance allele frequency in the field and to determine the biochemical and molecular basis of the resistance, which should provide further information to assist in the resistance management of S. frugiperda on transgenic maize producing B. thuringiensis proteins.

Efficiency of biological control for fall armyworm resistant to the protein Cry1F

“…After five days, the caterpillars were separated in 50 mL cups containing artificial diet and sealed with acrylic lids until the emergence of adults. Neonate S. frugiperda caterpillars selected in terms of resistance to the protein Cry1F were maintained according to Leite et al (2016).…”

Transfer of Cry1F from Bt maize to eggs of resistant Spodoptera frugiperda

“…The Cry1F resistant population of S . frugiperda used in this work was selected by Leite et al [ 18 ]. It was reared in the laboratory of Ecotoxicology and Insect Management (Embrapa Maize and Sorghum) at 25± 2°C, 12:12 h L:D and 60 ±10% RH, according to the methodology used by the same authors [ 18 ].…”

“…frugiperda used in this work was selected by Leite et al [ 18 ]. It was reared in the laboratory of Ecotoxicology and Insect Management (Embrapa Maize and Sorghum) at 25± 2°C, 12:12 h L:D and 60 ±10% RH, according to the methodology used by the same authors [ 18 ]. This population can complete development on excised leaves of Bt maize, and resistance is autosomal, incompletely recessive with simple monogenic inheritance [ 18 ], similar to resistance in this species found throughout Brazil [ 15 , 19 , 20 ].…”

“…It was reared in the laboratory of Ecotoxicology and Insect Management (Embrapa Maize and Sorghum) at 25± 2°C, 12:12 h L:D and 60 ±10% RH, according to the methodology used by the same authors [ 18 ]. This population can complete development on excised leaves of Bt maize, and resistance is autosomal, incompletely recessive with simple monogenic inheritance [ 18 ], similar to resistance in this species found throughout Brazil [ 15 , 19 , 20 ]. Indeed, eight Brazilian resistant colonies that were independently isolated from all areas of the maize growing region of the country (from Bahia, in the northeast, to Paraná, in the south) were found to carry the same resistance allele [ 15 ], so the genetic basis of resistance for S .…”

Produção de microescleródios de >i<Metarhizium>/i< spp. para inoculação de sementes de milho visando o controle de >i<Spodoptera frugiperda>/i< (Lepidoptera: Noctuidae)

“…Entretanto, relatos no Brasil e no mundo da evolução no processo de populações de insetos resistentes à tecnologia comprometeram a eficácia da utilização desses eventos (STORER et al, 2010;FARIAS et al, 2014;LEITE et al, 2016 (NAULT, 1980;OLIVEIRA et al, 1998 (WEBB et al, 1999;CHRISTENSEN et al, 2005;HOGENHOUT et al, 2008 , 2004;BATISTA-PEREIRA et al, 2006;BAUDRON et al, 2019). As lagartas durante o processo de alimentação danificam plantas de milho desde a emergência da plântula até a formação de espigas (CRUZ, 1995 Produção de conídios foi superior (8,5×10 9 conídios g -1 de MS) quando o MS foi obtido em meio mais rico em nitrogênio (relação C:N de 30:1) que MS obtido em meio mais pobre com relação C:N de 50:1 (5,5×10 9 conídios g -1 de MS) (BEHLE; JACKSON, 2014).…”