Functional dominance and monitoring of Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) resistance to Bt technologies in Brazil

Plantas transgênicas que expressam toxinas de Bacillus thuringiensis Berliner (Bt) têm sido amplamente utilizadas para o controle de Spodoptera frugiperda (J. E. Smith) no Brasil. Entretanto, a evolução da resistência é um dos maiores entraves para a continuidade do uso desta tecnologia. Para subsidiar programas de Manejo da Resistência de Insetos (MRI), foram conduzidos estudos para o aprimoramento dos programas de manejo da resistência de S. frugiperda a tecnologias Bt. Foram realizadas estudos para determinar a dominância funcional da resistência de S. frugiperda a tecnologias Bt mediante a avaliação da sobrevivência de larvas neonatas provenientes das linhagens de S. frugiperda resistentes ao milho Herculex® que expressa a proteína Cry1F (HX-R), ao milho YieldGard VT PRO™ que expressa as proteínas Cry1A.105 e Cry2Ab2 (VT-R), ao milho PowerCore™ que expressa as proteínas Cry1A.105, Cry2Ab2 e Cry1F (PW-R), e ao milho Agrisure Viptera™ que expressa a proteína Vip3Aa20 (Vip-R), além da linhagem suscetível (Sus) e de suas respectivas linhagens heterozigotas em diversas tecnologias de milho e algodão Bt. Posteriormente, um método prático para o monitoramento fenotípico da suscetibilidade a diferentes tecnologias de milho e algodão Bt foi testado a partir da avaliação da sobrevivência de larvas neonatas em folhas de plantas Bt em populações de S. frugiperda provenientes dos Estados do Rio Grande do Sul, Paraná, São Paulo, Goiás e Bahia na safra agrícola 2014/15. E por último, a estimativa da frequência de alelos de resistência de S. frugiperda a Vip3Aa20 foi validada pelo método de F1 screen. Em geral, observou-se alta mortalidade dos heterozigotos nas tecnologias Bt testadas, comprovando que a resistência de S. frugiperda a proteínas Bt é funcionalmente recessiva o que suporta a estratégia de refúgio em programas de MRI. Verificou-se também que linhagens resistentes a eventos que expressam proteínas Cry não sobrevivem em tecnologias que expressam proteína Vip. No monitoramento prático da suscetibilidade a tecnologias Bt, sobrevivência larval superior a 70% foi observada para populações de campo do Paraná, Goiás e Bahia no milho Herculex®. Em tecnologias de milho PowerCore™ e YieldGard VT PRO™ houve sobrevivência larval variando de 1,1 a 17,9%. Em contraste, não houve sobreviventes em tecnologias de milho Viptera™. Em algodão WideStrike® que expressa as proteínas Cry1Ac e Cry1F, sobrevivência acima de 41% foi observada para populações de campo de S. frugiperda. A sobrevivência larval em Bollgard II® que expressa as proteínas Cry1Ac e Cry2Ab2 variou de 14 a 40%. No algodão TwinLink® que expressa as proteínas Cry1Ab e Cry2Ae, a sobrevivência larval das populações foi menor que 20%. O método de F1 screen foi eficiente na detecção de alelos de resistência a Vip3Aa20 em populações de S. frugiperda provenientes de diferentes regiões produtoras de milho no Brasil na safra 2014/2015. De 263 isofamílias testadas, foram detectadas três isofamílias positivas oriundas do Paraná, Mato Grosso e Goiás. A frequência de resistência estimada a Vip3Aa20 variou de 0,0140 a 0,0367 nas populações avaliadas, sendo que a frequência total foi de 0,0076. Neste estudo, fornecemos informações para refinar as estratégias de MRI, além de introduzir novas técnicas para monitorar a resistência de S. frugiperda a tecnologias Bt no Brasil.Transgenic plants expressing toxins from Bacillus thuringiensis Berliner (Bt) have been widely used to the control of Spodoptera frugiperda (J. E. Smith) in Brazil. However, the resistance evolution is one of the major threats to the continuous use of this technology. To subsidize Insect Resistance Management (IRM), studies were conducted to improve S. frugiperda resistance management programs to Bt technologies. Studies to determine functional dominance of resistance of S. frugiperda to Bt technologies were conducted by evaluating neonate larval survival of S. frugiperda strains resistant to Herculex® maize expressing Cry1F protein (HX-R), to YieldGard VT PRO™ maize expressing Cry1A.105 and Cry2Ab2 proteins (VT-R), to PowerCore™ maize expressing Cry1A.105, Cry2Ab2 and Cry1F proteins (PW-R) and to Agrisure Viptera™ maize expressing Vip3Aa20 protein (Vip- R), in addition to susceptible strain (Sus) and the respective heterozygous strains in several Bt maize and cotton technologies cultivated in Brazil. Then, a practical method for phenotypic resistance monitoring of several Bt maize and cotton were tested, based on neonate larval survival on Bt leaf tissue in S. frugiperda populations collected from Rio Grande do Sul, Paraná, São Paulo, Goiás and Bahia States. Finally, the F1 screen method was validated to estimate the frequency of Vip3Aa20 resistance alleles in S. frugiperda. In general, high mortality of heterozygous individuals was observed on Bt technologies, confirming that resistance of S. frugiperda to Bt proteins is functionally recessive and supporting the importance of refuge areas in IRM programs. No larval survival on Vip expressing maize was found with strains of S. frugiperda resistant to maize expressing Cry toxins. In the practical resistance monitoring, more than 70% of larval survival in field populations of S. frugiperda from Paraná, Goiás and Bahia was detected in Herculex® maize. Larval survival on PowerCore™ and YieldGard VT PRO™ maize technologies ranged from 1.1 to 17.9%. In contrast, no larval survival of field populations was observed on Viptera™ maize technologies. On WideStrike® cotton, more than 41% larval survival was observed in field populations of S. frugiperda. The larval survival was on Bollgard II® ranged from 14 to 40%. In TwinLink® the larval survival was lower than 20%. The F1 screen method was efficient in detecting Vip3Aa20 resistance alleles in field populations of S. frugiperda. From a total of 263 isofamily lines tested, three positive isofamily lines from Paraná, Mato Grosso and Goiás were found. The frequency of Vip3Aa20 resistance alleles ranged from 0.0140 to 0.0367, with overall frequency of 0.0076. In this study, we provide valuable information to improve IRM strategies and propose new methods to monitor resistance of S. frugiperda to Bt technologies in Brazil

Dinâmica de lepidópteros-praga e abordagem filogeográfica de três espécies de Spodoptera (Lepidoptera: Noctuidae) na cultura da soja no Brasil

Soybean is one of the most important sources of oil and protein worldwide. The area planted with soybean significantly increased in the last 50 years, and currently, Brazil is the largest producer. Several agricultural innovations were needed to increase production such as no-tillage system cultivation, soil acid correction and fertilization, new crop varieties adapted to a range of latitudes, inoculation of nitrogen-fixing bacteria, multi-crop system with at least two cropping seasons per year and the use of genetically modified plants. The soybean technology MON 87701 × MON 89788, expressing Cry1Ac and conferring tolerance to glyphosate has been widely adopted in Brazil since 2013. However, pest shifts or resistance evolution could reduce the benefits of this technology. Despite the importance to Integrated Pest Management, knowledge on the population dynamics, shifts and genetic structure of agriculture pest populations in Brazil are still incipient. Here, is presented evidence of the regional reduction in insecticide use across areas in Brazil where Cry1Ac soybean is grown, with up to 50% reduction in the number of insecticide applications for managing lepidopteran pests on non-Bt soybean observed at specific locations. Furthermore, a reduced number of Chrysodeixis includens moths were captured across years in a pest-monitoring study in four mesoregions. The number of Helicoverpa spp. moths captured also were reduced at three mesoregions. In a large-scale sampling of larvae on commercial soybean fields during the 2019 and 2020 crop seasons, C. includens was the main lepidopteran pest in non-Bt fields. More than 98% of larvae found in Cry1Ac soybean were Spodoptera spp., although the numbers of Spodoptera spp. were similar between Cry1Ac soybean and non-Bt fields. Cry1Ac soybean provided a high level of protection against Anticarsia gemmatalis, C. includens, Chloridea virescens and Helicoverpa spp. To investigate the population genetic diversity, population structure, and demographic pattern of Spodoptera eridania, Spodoptera cosmioides and Spodoptera frugiperda, a mitochondrial COI sequence-based analyzes were performed. High genetic diversity was observed for S. eridania sampled on soybean in Brazil. The genetic diversity index of S. eridania was higher than that observed for S. cosmioides and S. frugiperda. Low genetic structure was observed for the three Spodoptera species. The highest 𝝫ST observed was for S. cosmioides (0.058) followed by for S. eridania (0.058) and S. frugiperda (0.017). There is evidence that the three Spodoptera species evaluated in this study are in demographic and spatial expansion. The results of the study also suggest that corn strain is the major lineage of S. frugiperda occurring in soybean in Brazil. This research clarified and updated the knowledge of insect pest populations attacking soybean in Brazil. A regional suppression of lepidopteran pests and reduced insecticide use with the widespread adoption of Cry1Ac soybean has been observed, bringing economic and environmental benefits. Chrysodeixis includens and A. gemmatalis continue to be primary lepidopteran pests of soybean in Brazil and Cry1Ac soybean continues to effectively manage the target lepidopteran pests. Increase in the relative abundance of non-target Spodoptera spp. larvae in both non-Bt and Cry1Ac soybeans confirmed the emerging importance of this genera in soybean. Finally, these Spodoptera species show low genetic structure and are at demographic and spatial expansion, probably driven by agriculture expansion, especially soybean fields.A soja é uma das fontes mais importantes de óleo e proteína em todo o mundo. A área plantada com soja aumentou significativamente nos últimos 50 anos e, atualmente, o Brasil é o maior produtor mundial. Várias inovações agrícolas foram necessárias para aumentar a produção, tais como o sistema de plantio direto, correção da acidez do solo e adubação, novas variedades adaptadas a várias latitudes, inoculação de bactérias fixadoras de nitrogênio, sistema de multiculturas com pelo menos duas safras por ano e o uso de plantas geneticamente modificadas. A tecnologia de soja MON 87701 × MON 89788, que expressa a proteína Cry1Ac e confere a tolerância ao herbicida glifosato, vem sendo amplamente adotada no Brasil desde 2013. No entanto, mudanças na composição de pragas ou a evolução de resistência podem reduzir os benefícios desta tecnologia. Apesar da importância no Manejo Integrado de Pragas, o conhecimento sobre a dinâmica populacional, mudanças na composição e a estrutura genética das populações de pragas agrícolas no Brasil ainda são incipientes. Neste trabalho, são apresentadas evidências da redução regional no uso de inseticidas em áreas no Brasil onde a soja Cry1Ac é cultivada, com redução de até 50% no número de aplicações de inseticidas para o manejo de lepidópteros-praga em soja não-Bt, observado em locais específicos. Além disso, um número reduzido de adultos de Chrysodeixis includens foi capturado ao longo dos anos em um estudo de monitoramento de pragas em quatro mesorregiões. O número de adultos de Helicoverpa spp. capturados também foi reduzido em três mesorregiões. Em uma amostragem em larga escala de lagartas em lavouras comerciais de soja durante as safras de 2019 e 2020, C. includens foi o principal lepidóptero-praga presente em áreas não-Bt. Mais de 98% das lagartas encontradas na soja Cry1Ac foram representadas por Spodoptera spp., embora os números de Spodoptera spp. foram semelhantes entre os campos de soja Cry1Ac e não-Bt. A soja Cry1Ac resultou em um alto nível de proteção contra Anticarsia gemmatalis, C. includens, Chloridea virescens e Helicoverpa spp. Para investigar a diversidade genética, estrutura populacional e demografia de Spodoptera eridania, Spodoptera cosmioides e Spodoptera frugiperda, foram realizadas análises baseadas na sequência do COI mitocondrial. Alta diversidade genética foi observada para S. eridania amostrada em soja no Brasil. O índice de diversidade genética de S. eridania foi superior em relação aos valores observados para S. cosmioides e S. frugiperda. Baixa estrutura genética foram observadas para as três espécies de Spodoptera. O maior &#120683ST observado foi para S. cosmioides (0,058) seguido por S. eridania (0,058) e S. frugiperda (0,017). Há evidências de que as três espécies de Spodoptera avaliadas neste estudo estão em expansão demográfica e espacial. Os resultados do estudo também sugerem que a linhagem milho é a principal linhagem de S. frugiperda que ocorre na cultura da soja no Brasil. Esta pesquisa clarificou o conhecimento sobre as populações de insetos-praga que atacam a cultura da soja no Brasil. Foi observado uma supressão regional de lepidópteros-praga e redução do uso de inseticidas relacionado com a alta adoção da soja Cry1Ac, trazendo benefícios econômicos e ambientais. Chrysodeixis includens e A. gemmatalis continuam sendo os principais lepidópteros-praga da soja no Brasil e a soja Cry1Ac continua a oferecer proteção contra as pragas-alvo. O aumento da abundância relativa de Spodoptera spp. em soja não-Bt e Cry1Ac confirmou o aumento da importância deste gênero na soja. Por fim, estas espécies de Spodoptera apresentam baixa estrutura genética e estão em expansão demográfica e espacial, provavelmente impulsionadas pela expansão da agricultura, principalmente com lavouras de soja

Biological activity of Bt proteins expressed in different structures of transgenic corn against Spodoptera frugiperda

ABSTRACT: Spodoptera frugiperda (J. E. Smith) is the main target pest of Bt corn technologies, such as YieldGard VT PRO(tm) (Cry1A.105/Cry2Ab2) and PowerCore(tm) (Cry1A.105/Cry2Ab2/Cry1F). In this study, it was evaluated the biological activity of Bt proteins expressed in different plant structures of YieldGard VT PRO(tm) and PowerCore(tm) corn against S. frugiperda . Complete mortality of S. frugiperda neonates was observed on leaf-disc of both Bt corn technologies. However, the mortality in silks and grains was lower than 50 and 6%, respectively. In addition, more than 49% of the surviving larvae in silks and grains completed the biological cycle. However, all life table parameters were negatively affected in insects that developed in silks and grains of both Bt corn events. In summary, the low biological activity of Bt proteins expressed on silks and grains of YieldGard VT PRO(tm) and PowerCore(tm) corn can contribute to the resistance evolution in S. frugiperda populations

Transcript expression plasticity as a response to alternative larval host plants in the speciation process of corn and rice strains of Spodoptera frugiperda

Our main purpose was to evaluate the expression of plastic and evolved genes involved in ecological speciation in the noctuid moth Spodoptera frugiperda, the fall armyworm (FAW); and to demonstrate how host plants might influence lineage differentiation in this polyphagous insect. FAW is an important pest of several crops worldwide, and it is differentiated into host plant-related strains, corn (CS) and rice strains (RS). RNA-Seq and transcriptome characterization were applied to evaluate unbiased genetic expression differences in larvae from the two strains, fed on primary (corn) and alternative (rice) host plants. We consider that genes that are differently regulated by the same FAW strain, as a response to different hosts, are "plastic". Otherwise, differences in gene expression between the two strains fed on the same host are considered constitutive differences. Individual performance parameters (larval and pupal weight) varied among conditions (strains vs. hosts). A total of 3657 contigs was related to plastic response, and 2395 contigs were differentially regulated in the two strains feeding on preferential and alternative hosts (constitutive contigs). Three molecular functions were present in all comparisons, both down-and up-regulated: oxidoreductase activity, metal-ion binding, and hydrolase activity. Metabolization of foreign chemicals is among the key functions involved in the phenotypic variation of FAW strains. From an agricultural perspective, high plasticity in families of detoxifying genes indicates the capacity for a rapid response to control compounds such as insecticides18CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPsem informação2012/16266-7; 2011/00417-

Transcript expression plasticity as a response to alternative larval host plants in the speciation process of corn and rice strains of Spodoptera frugiperda

Abstract Background Our main purpose was to evaluate the expression of plastic and evolved genes involved in ecological speciation in the noctuid moth Spodoptera frugiperda, the fall armyworm (FAW); and to demonstrate how host plants might influence lineage differentiation in this polyphagous insect. FAW is an important pest of several crops worldwide, and it is differentiated into host plant-related strains, corn (CS) and rice strains (RS). RNA-Seq and transcriptome characterization were applied to evaluate unbiased genetic expression differences in larvae from the two strains, fed on primary (corn) and alternative (rice) host plants. We consider that genes that are differently regulated by the same FAW strain, as a response to different hosts, are “plastic”. Otherwise, differences in gene expression between the two strains fed on the same host are considered constitutive differences. Results Individual performance parameters (larval and pupal weight) varied among conditions (strains vs. hosts). A total of 3657 contigs was related to plastic response, and 2395 contigs were differentially regulated in the two strains feeding on preferential and alternative hosts (constitutive contigs). Three molecular functions were present in all comparisons, both down- and up-regulated: oxidoreductase activity, metal-ion binding, and hydrolase activity. Conclusions Metabolization of foreign chemicals is among the key functions involved in the phenotypic variation of FAW strains. From an agricultural perspective, high plasticity in families of detoxifying genes indicates the capacity for a rapid response to control compounds such as insecticides

Cross-Resistance between Cry1 Proteins in Fall Armyworm (Spodoptera frugiperda) May Affect the Durability of Current Pyramided Bt Maize Hybrids in Brazil.

Genetically modified plants expressing insecticidal proteins from Bacillus thuringiensis (Bt) offer valuable options for managing insect pests with considerable environmental and economic benefits. Despite the benefits provided by Bt crops, the continuous expression of these insecticidal proteins imposes strong selection for resistance in target pest populations. Bt maize (Zea mays) hybrids have been successful in controlling fall armyworm (Spodoptera frugiperda), the main maize pest in Brazil since 2008; however, field-evolved resistance to the protein Cry1F has recently been reported. Therefore it is important to assess the possibility of cross-resistance between Cry1F and other Cry proteins expressed in Bt maize hybrids. In this study, an F2 screen followed by subsequent selection on MON 89034 maize was used to select an S. frugiperda strain (RR) able to survive on the Bt maize event MON 89034, which expresses the Cry1A.105 and Cry2Ab2 proteins. Field-collected insects from maize expressing the Cry1F protein (event TC1507) represented most of the positive (resistance allele-containing) (iso)families found. The RR strain showed high levels of resistance to Cry1F, which apparently also conferred high levels of cross resistance to Cry1A.105 and Cry1Ab, but had only low-level (10-fold) resistance to Cry2Ab2. Life history studies to investigate fitness costs associated with the resistance in RR strain revealed only small reductions in reproductive rate when compared to susceptible and heterozygous strains, but the RR strain produced 32.2% and 28.4% fewer females from each female relative to the SS and RS (pooled) strains, respectively. Consistent with the lack of significant resistance to Cry2Ab2, MON 89034 maize in combination with appropriate management practices continues to provide effective control of S. frugiperda in Brazil. Nevertheless, the occurrence of Cry1F resistance in S. frugiperda across Brazil, and the cross-resistance to Cry1Ab and Cry1A.105, indicates that current Cry1-based maize hybrids face a challenge in managing S. frugiperda in Brazil and highlights the importance of effective insect resistance management for these technologies

Comparison of fitness components of life stages of <i>S</i>. <i>frugiperda</i> strains reared on non-Bt corn.

<p>Within each development stage, bars with the same letter are not significantly different (LSD <i>t</i>-test; <i>P</i> > 0.05).</p

Concentration-response and growth inhibition response (MIC₅₀ and EC₅₀; ng/cm²) of <i>S</i>. <i>frugiperda</i> in diet-overlay bioassays with purified Cry1A.105 and Cry2Ab2 proteins.

<p>^a MIC₅₀: Concentration that inhibits molting to second instar in 50% of individuals after 7 days.</p><p>^b<i>P</i> > 0.05 in the goodness-of-fit test.</p><p>^c Resistance Ratio = (MIC₅₀ or EC₅₀ of indicated strain)/(MIC₅₀ or EC₅₀ of SS strain).</p><p>^d EC₅₀: Effective concentration of protein required to cause 50% growth inhibition at 7 days.</p><p>Concentration-response and growth inhibition response (MIC₅₀ and EC₅₀; ng/cm²) of <i>S</i>. <i>frugiperda</i> in diet-overlay bioassays with purified Cry1A.105 and Cry2Ab2 proteins.</p

Survival of <i>S</i>. <i>frugiperda</i> on leaf discs of different Bt and non-Bt maize plants.

<p>Values represent means ± SE. A separate ANOVA (Tukey’s test, <i>P</i>≤0.05) was conducted for treatments within each column (means followed by the same letter in column are not significantly different).</p><p>^a Mean weight of survivors.</p><p>^b Weight reduction compared to control (non-Bt).</p><p>n.a. Not applicable</p><p>Survival of <i>S</i>. <i>frugiperda</i> on leaf discs of different Bt and non-Bt maize plants.</p