Detection of cry1 genes in Bacillus thuringiensis isolates from South of Brazil and activity against Aanticarsia gemmatalis (Lepidoptera:Noctuidae)

Abstract

The bacterium Bacillus thuringiensis (Bt) is characterized by its ability to produce proteic crystalline inclusions during sporulation. Cry1 protein has insecticidal activity and is highly specific to certain insects and not toxic to unrelated insects, plants or vertebrates. In this work, the patogenicity of twelve Bt isolates was tested against Anticarsia gemmatalis, one of the most important insect pests of soybeans. Spore-crystal complex was applied to the surface of artificial diets and the mortality of A. gemmatalis larvae was assessed seven days after each treatment. When compared to a control Bt isolate known by its high toxicity to A. gemmatalis larvae, four novel Bt isolates exhibited even higher toxic activities against the insect, resulting in more than 90% mortality. PCR was used to amplify DNA fragments related to known cry1 genes. Bt strains with high toxicity produced expected PCR products of around 280 bp, whereas non-toxic or low toxic strains did not produce any PCR product or showed amplified fragments of different sizes. Toxic Bt isolates also exhibited an expected protein profile when total protein extracts were evaluated by SDS-PAGE.

Selection and molecular characterization of Bacillus thuringiensis strains efficient against soybean looper (Chrysodeixis includens) and Spodoptera species

“…Several lepidopterans species respond differently to the proteins tested, allowing to divide into groups of more permissive or less permissive to the activation of B. thuringiensis toxins (Van Frankenhuyzen, 2009). An important aspect is the selection B. thuringiensis strains with high toxic activity for more than one pest and that produce proteins with different modes of action for obtaining new formulations to be used in agriculture (Bobrowski et al, 2001;Bobrowski et al, 2003).…”

cry Genes profiling and the toxicity of isolates of Bacillus thuringiensis from soil samples against American bollworm, Helicoverpa armigera

“…This heat shock step was repeated twice to lyse the cells. The resulting cell lysate was centrifuged at 12 406 g for 5 min (Minispin plus Eppendorf AG centrifuge 22331, Vernon Hills, IL), and freshly prepared supernatant was used as DNA sample in the PCR (Bobrowski et al 2001). For detection of eight different cry genes, specific primers (Table 1) were used (Ben-Dov et al 1997;Alberola et al 1999).…”

Bacillus thuringiensis isolates entomopathogenic for Culex quinquefasciatus (Diptera: Culicidae) and Anticarsia gemmatalis (Lepidoptera: Noctuidae)

“…Bioassays have been used to examine new B. thuringiensis isolates from soil, leaves and insects that induce mortality in dipterous and lepidopterous insects and are equal, or superior, to B. thuringiensis reference strain B.thuringiensis IPS-82 and kurstaki strain HD-1 (Bobrowski et al, 2001;Jara et al, 2006).…”

“…Regarding the isolates recovered from A. ignicans, it should be pointed out that Monnerat et al (2002) and Porcar and Caballero (2000) obtained isolates from lepidoptera with high toxic activity against S. frugiperda, H. armigera and S. littoralis. Several authors have also reported that soil can be a source of entomopathogenic B. thuringiensis isolates with toxicity against lepidoptera (Silva et al, 2004;Praça et al, 2004;Bobrowski et al, 2001).…”