Autor(es): El-kersh, T. A.; Al-akeel, R. A.; Al-sheikh, Y. A.; Alharbi, S. A.

Resumo: A total of 157 environmental samples were collected from 11 ecological regions across Saudi Arabia to isolate native Bacillus thuringiensis (Bt) strains. Bt isolates (n=103) were recovered by the 50% (v/v) ethanol treatment method with Bt index range of 0.01 to 0.4. Most of Bt isolates showed spherical crystals (54%), while, irregular, bi-pyramidal, and spore-attached crystal constituted 27, 16 and 3% respectively. PCR analysis with eight general and specific dipteran primers of Cry and Cyt genes, revealed positive amplification for cry4 & cyt1, and cry4A, cry4B and cyt2, and cry 10 and cry 11 genes in 28%, 26%, 22%, and 25% of tested strains respectively; whereas cry2 gene was not detected except with the reference Bt kurstaki HD-1 strain. Bioassays against Aedes caspuis and Culex pipiens larvae indicated that 11 strains displayed better larvicidal activity compared with Bacillus thuringiensis H14 (Bti) reference (LC50 0.6 mu g/ml) strain against Ae. caspuis, but only two strains (620A & 633R1, LC50 of 0.09 mu g/ml & 0.064 mu g/ml) that gave significant enhancement. Additionally, one strain (633R1) showed LC50 similar to that of Bti H14 (LC50 0.064 mu g/ml) against Cx. pipiens. With the exception of cyt primers, Sequenced DNA of all positive primers amplicons revealed 95 to 99% identity in GenBank with Bacillus thuringiensis subsp. israelensis plasmid pBtoxis and also correlated with its SDS-PAGE expressed protein profiles analysis. It is hoped that our wild bio-insecticide Bt strains can be explored in future in the control of mosquito-vector borne diseases in Saudi Arabia.

Palavras-Chave: Culex-Quinquefasciatus; Insecticidal Activity; Aedes-Aegypti; Subsp Israelensis; Toxicity; Larvae; Soil; Diversity; Synergism; Protein

Imprenta: Tropical Biomedicine, v. 31, n. 4, p. 616-632, 2014

Descritores: Aedes aegypti - DNA

Data de publicação: 2014