Abstract

MARTINEZ O, WILSON; URIBE V, DANIEL  and  CERON S, JAIRO. Efecto tóxico de proteínas Cryl de Bacillus thuringiensis sobre larvas de Teda solanivora (Lepidoptera Gelechiidae)Bacillus thuringiensis Cryl proteins toxic effect against Teda solanivora (Lepidoptera: Gelechiidae). Rev. Colomb. Entomol. [online]. 2003, vol.29, n.1, pp.89-93. ISSN 0120-0488.

In the last decade Teda solanivora Povolny has become one of the most significant pest in Colombian potato growing áreas. In the past T. solanivora control strategies have been developed using chemical pesticides, although recently some alternative biológica! control and crop management practices have been used. The use of entomopathogenic microorganisms such as baculovirus and bacteria for T. solanivora control offers a new useful tool for developing an intégrate pest management program, Earlier works explored the potential use of Badllus thuringiensis strains in T, solanivora control. However, Bt Cry proteins specific to this insect have not been yet identified. In accordance with this, we analyzed the specificity of 7 Bt Cryl proteins (CrylAa, CrylAb, CrylAc, CrylBa, CrylCa, CrylDa and CrylEa) toward the first instar T. solanivora larvae. At the same time we designed an easy and reproducible bioassay method based in natural diet. Proteins were evaluated at 4 ug/cm² dose, which was the LC₅₀ of HD1 strain, used as a positive control in bioassays. Results showed a higher toxicity of CrylAc compared with the other Cryl proteins evaluated. CrylAc caused a 20% average mortality while no more than 7% were obtained with the rest of the proteins. In order to confirm these findings we evaluated HD73 strain which posses only CrylAc and Cry2A genes and recombinant E. coli strain with only Cry2A gene. As we expected, the bioassays indicated a high toxicity of HD73 and low toxicity of Cry2A protein, showing average moralities over 70% and below 10%, respectively. Results indicated that CrylAc is specific to T. solanivora, however, it seems that interaction with other proteins enhances CrylAc activity as observed in bioassays with HD1 and HD73 strains where Cryl proteins besides CrylAc are present.

Keywords : Polilla guatemalteca; Bioassays; Toxins; Biological control.

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