Identificação através de PCR dos genes CryI de cepas de Bacillus thuringiensis Berliner eficientes contra a lagarta do cartucho, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

Abstract

An. Soc. Entomol. Brasil 29(1): 147-153 (2000) PCR Identification of Cry I Genes in Bacillus thuringiensis Strains that are Efficient Against Fall Armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)ABSTRACT -Fall armyworm, Spodoptera frugiperda (J. E. Smith), is the most important maize insect pest in Brazil and its damage can reduce yield up to 34%. The objective of this work was to utilize the PCR technique to Identify Bacillus thuringiensis (B.t) strains that control S. frugiperda in maize crops. Bioassays showed that 16 strains were very effective against S. frugiperda, 15 of them collected from soil samples and one (T09) obtained at the Institute Pasteur. The DNA of these strains were probed with cryI general primers and their proteins were analised by SDS-PAGE eletrophoresis. All strains present positive results for cryI genes. To further characterize these strains, specific cryI primers were employed. PCR technique showed that some strains harbour the same cryI genes. The only difference was the amplification of an unexpected fragment of approximately 160bp when a mixture of cryIB and cryID specific primers was used. Analysis by phase contrast microscope showed that crystal proteins produced by these strains were all bipyramidal crystals. Also, eltrophoretic analysis of proteins by SDS-PAGE showed the same protein banding pattern for most of the strains.

Requirement of Simultaneous Assessment of Crystal- and Supernatant-Related Entomotoxic Activities of Bacillus thuringiensis Strains for Biocontrol-Product Development

“…Moreover, previous studies had shown clear advantages for this specific composition of Cry proteins (including Cry1E) on the toxicity to S. frugiperda under tropical conditions [26]. Therefore, on the basis of preliminary studies [26,44] and on the laboratory and field bioassays of this work, the Btt 01 strain showed a great potential for use in biocontrol applications, mostly in the form of biopesticides based on parasporal inclusions of proteinaceous (hence thermolabile) nature.…”

“…Because of this health and environmental threat, the World Health Organization has prohibited the use of Bt strains producing this toxin in bioinsecticide formulations [50], though some countries still use β-exotoxin products in specific control programs of flies that are resistant to other insecticides [51]. Considering the positive results of this study in relation to the potential use of this tropical strain in biocontrol strategies, based on its δ-endotoxins composition [25,26,44] and action in the field, it is here postulated that the assessment of Bt collections also for the presence of β-exotoxins appears to be a necessary routine in research labs and companies producing Bt -based bioinsecticides. One can, for example, include tests with SN-heated aliquots [28,31,32] to assess for entomotoxicity and thermostability; once the latter is detected, further inactivation-based characterization such as those employed here can be used.…”

Molecular Characterization of Bacillus thuringiensis cyt Genes and Their Effect Against Fall Armyworm, Spodoptera frugiperda

“…The isolates containing cyt genes identified in this study showed different levels of toxicity against S. frugiperda (Valicente et al, 2000;Valicente & Barreto, 2003;Valicente & Fonseca, 2004;Valicente et al, 2010). Two isolates caused 100% mortality (isolates 1646JAB and 1656JAB) and one caused 79% of larval mortality (strain 1168C).…”

Bactérias isoladas de culicídeos (Diptera: Nematocera) hematófagos em Belém, Pará, Brasil

“…Studies performed 20 with mosquitoes bred in insectariums in Mexico and 24 Brazil showed the presence of Gram-negative bacteria in their intestines. Some bacteria are being used as biological 13,49,5,50 pest control of adult insects and larvae in plantations , while others are being tested as an alternative to controlling transmission by various insects . In a 2007 study , more than 20 bacteria species were isolated from horseflies and preserved, including those belonging to the Staphylococcus, Streptococcus and Serratia genera.…”