Abstract
Chemical insecticides may be toxic and cause environmental degradation. Consequently, biological control for insects represents an alternative with low ecological impact. In this work, three soil isolates (A21, A51 and C17) from different regions of the Cuban archipelago were identified, characterized and evaluated against Aedes aegypti and Culex quinquefasciatus. The new isolates were compared with reference IPS82 strain and two strains isolated from biolarvicides Bactivec and Bactoculicida, respectively. The differentiation was done by morphological, biochemical, bioassays activity and molecular methods (SDS-PAGE, plasmid profile and random amplified polymorphic analysis). All isolates were identified as Bacillus thuringiensis. The A21, A51 and C17 isolates showed higher larvicide activity than Bactivec's isolated reference strain, against both A. aegypti and C. quinquefasciatus. A21 isolate had a protein profile similar to IPS82 and Bactivec strain. A51 and C17 isolates produced a characteristic proteins pattern. A21 and A51 isolates had plasmid patterns similar to IPS82 standard strain, while C17 isolate had different both plasmid profile and protein bands. All the studied isolates showed a diverse RAPD patterns and were different from the strains previously used in biological control in Cuba.
Highlights
The biological control has been accepted as an alternative as part of the integrate pest management, with a low environmental impact (Nunes & Fiuza 2003)
All the native isolates showed a better CL50 against both A. aegypti and C. quinquefasciatus than reference strain (Bactivec)
The phenotypic methods used for classifying B. thuringiensis, H-serotyping and biochemical characters, have both contributed to the establishment of an useful classification (Iriarte et al 2000, Khyami-Horani et al 2003)
Summary
The biological control has been accepted as an alternative as part of the integrate pest management, with a low environmental impact (Nunes & Fiuza 2003). The use of entomopathogenic bacteria like Bacillus thuringiensis as larvicides is a viable alternative for insect control. Intensive screening programs have isolated and characterized B. thuringiensis from soil samples, plant surface, dead insects, stored grains and aquatic habitats (Bravo et al 1998, ReyesRamirez & Ibarra 2005, Reyes-Ramirez & Ibarra 2008). The entomopathogenic activity of this bacterium is principally due to the presence of proteinaceous inclusions known as insecticidal crystal proteins (Cry proteins). These Cry proteins are coded by cry genes harbored in megaplasmid and they exhibit a variety of biological actions, including cytolitic, haemolytic action, in addition to entomocidal activities (Lima et al 2002). We identified, characterized and evaluated the insecticidal activity of Bacillus environmental isolates from different regions of the Cuban archipelago
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