Genetic Variability of Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) Populations from Latin America Is Associated with Variations in Susceptibility to Bacillus thuringiensis Cry Toxins

Abstract

Bacillus thuringiensis strains isolated from Latin American soil samples that showed toxicity against three Spodoptera frugiperda populations from different geographical areas (Mexico, Colombia, and Brazil) were characterized on the basis of their insecticidal activity, crystal morphology, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of parasporal crystals, plasmid profiles, and cry gene content. We found that the different S. frugiperda populations display different susceptibilities to the selected B. thuringiensis strains and also to pure preparations of Cry1B, Cry1C, and Cry1D toxins. Binding assays performed with pure toxin demonstrated that the differences in the toxin binding capacities of these insect populations correlated with the observed differences in susceptibility to the three Cry toxins analyzed. Finally, the genetic variability of the three insect populations was analyzed by random amplification of polymorphic DNA-PCR, which showed significant genetic diversity among the three S. frugiperda populations analyzed. The data presented here show that the genetic variability of S. frugiperda populations should be carefully considered in the development of insect pest control strategies, including the deployment of genetically modified maize in different geographical regions.Fall armyworm, Spodoptera frugiperda (J. E. Smith), is a worldwide pest of economic importance for different crops. This species has a highly polyphagous feeding behavior, which includes the consumption of different cultivated plants, such as maize (Zea mays L.), cotton (Gossypium hirsutum L.), and rice (Oryza sativa L.). To date, the most common method for controlling this pest relies on the use of synthetic insecticides such as methomyl, carbaryl, and cypermethrin (10), in spite of the damage they cause to the environment and to nontarget organisms. Two distinct strains of S. frugiperda, one associated with maize and the other with rice, have been already identified in the United States (17, 19). The detection and characterization of genetic diversity among insect populations is a critical issue for the improvement of pest management strategies, since the evolution of resistance to insecticides among insect populations is dependent on the frequency of resistant alleles, the inheritance of resistance, the relative fitness cost, and the gene flow.Bioinsecticides are viable alternatives for insect control in agriculture, and among them, Bacillus thuringiensis is the most widely used. B. thuringiensis is compatible with sustainable and environmentally friendly agricultural practices. This bacterium produces insecticidal proteins (Cry protoxins) during sporulation as parasporal crystals, which are highly specific to their target insects; safe for humans, other vertebrates, and plants; and biodegradable (12). Moreover, recombinant DNA technology using cry genes has developed insect-resistant transgenic plants that are used extensively for cotton, corn, and rice production, among others (23).Information regarding the suscept...

Comportamento de híbridos de milho transgênicos e respectivos híbridos isogênicos convencionais em relação à infestação de Spodoptera Frugiperda (j. E. Smith,1727) (Lepidoptera: Noctuidae) em duas localidades e épocas de semeadura

“…As pragas encontram-se dentre os inúmeros fatores que afetam a produtividade das plantas e, entre elas, destaca-se a lagarta-do-cartucho Spodoptera frugiperda (J. E. Smith, 1727) (Lepidoptera: Noctuidae), espécie de grande importância, não somente pelos danos que provoca, mas também pela dificuldade e baixa eficiência do controle químico (Boiça Junior et al, 1993;roel;Vendramim, 2006). Esse inseto ataca preferencialmente o cartucho das plantas de milho, consumindo grande parte da área foliar antes de as folhas se desenvolverem.…”

“…e a lagarta-da-espiga Helicoverpa zea (Boddie, 1850) (milfin, 1996;sieBert et al, 2008a Assim sendo, neste trabalho, objetivou-se avaliar o desempenho de híbridos comerciais de milho convencionais e seus isogênicos híbridos transgêni-cos que expressam as toxinas Cry1Ab (tecnologias Yieldgard® e Total Liberty®) e Cry1F (tecnologia Herculex®), com relação à infestação de lagartas de S. frugiperda e injúrias causadas às plantas, em sua fase fenológica de desenvolvimento em dois locais na estação de primavera-verão, e em uma região de cultivo na estação de outono ("safrinha").…”

Mitochondrial markers to distinguish Spodoptera frugiperda populations associated with corn and cotton crops

“…Other S. frugiperda mass-reared individuals were obtained from: Embrapa Recursos Genéticos e Biotecnologia, located in Brasília, DF, Brazil; Universidad Autónoma de México, located in Cuernavaca, Mexico; Corporación para Investigaciones Biológicas, located in Medellin, Colombia; and Universidad de Costa Rica, located in San José, Costa Rica. All these rearing strains were established with insects collected from corn crops in each country, and the insects were reared in artificial diet under laboratory conditions, at 28±2°C and 65±5% relative humidity, under a 12:12 (light-dark) photoperiod (Monnerat et al, 2006). DNA was extracted from insect samples according to the procedure in Agusti et al (1999).…”

“…For RAPD molecular analysis, approximately ten immature stages (second or third instar) of S. frugiperda were collected from different corn and cotton field crops. The RAPD reactions were done following the procedures described by Monnerat et al (2006), using the primers: OPA-01, OPA-02, OPA-03, OPA-04, OPA-05, OPA-07, OPA-10, OPA-11, OPA-13, OPA-14, OPA-15, OPA-17, OPA-20, OPE-01, OPE-03, OPE-07, OPE-08, OPE-14, OPE-15, OPR-01, OPR-02, OPR-03, OPR-04, OPR-05, OPR-07, OPR-10, and OPR-14; however, since seven (OPA-05, OPA-15, OPA-17, OPA-20, OPE-01, OPE-15, and OPR-05) of these primers did not generate useful PCR products, only 20 were analyzed. This experiment was repeated three times using randomly collected individuals.…”

Avaliação do risco de resistência de lepidópteros-praga (Lepidoptera: Noctuidae) à proteína Cry1Ac expressa em soja MON 87701 x MON 89788 no Brasil

“…Tempo ( (MONNERAT et al, 2006). Adicionalmente, uma quantidade insuficiente e/ou fraca ligação da proteína inseticida nos sítios de ligação do intestino médio também pode afetar a suscetibilidade a Cry1Ac, isso foi demonstrado para S. frugiperda a Cry1Ab (ARANDA et al, 1996) e S. exigua a Cry1C (de MAAGD et al, 2000), também pode estar relacionada com a inativação da proteína inseticida por proteases (MIRANDA; ZAMUDIO; BRAVO, 2001;RAHMAN et al, 2012 …”