Isolation, Characterisation And Bioefficacy Analysis Of Bacillus Thuringiensis (Bt) Strains Against Dengue Vectors
| dc.contributor.author | Ho, Lai Yee | |
| dc.date.accessioned | 2022-03-14T03:11:28Z | |
| dc.date.available | 2022-03-14T03:11:28Z | |
| dc.date.issued | 2021-03 | |
| dc.description.abstract | A mounting public health concern over mosquito-borne diseases, a global economic burden, and failure of current control measures due to escalating development of insecticides resistance have intensified the search for alternative ecofriendlier vector control strategies. An investigation was conducted to explore the toxicity profiles of indigenous B. thuringiensis isolates from an ex-tin mining area. Verification was performed through microscopic identification and biochemical characterisations. Morphological features of the crystal proteins were assessed using scanning and transmission electron microscopy. Distribution of insecticidal genes and crystal protein classes were examined through PCR and SDS-PAGE analyses. Eventually, these isolates were screened for larvicidal and sublethal efficacies against laboratory strains of Ae. albopictus and Ae. aegypti. From the seven sampling sites, 13 B. thuringiensis isolates were obtained (A10C, D10D, N6Bss, 6a3s, 8a3, 8a3s, 8b3, R1, R2, R3, D1C, A2B and C6D) with an overall B. thuringiensis index of 0.07. Spherical-shaped crystal proteins were present in all isolates, while lesser numbers of ovoidal- and cuboidal-shaped crystal proteins were noted. Protein profiles revealed presence of eight classes of crystal proteins (Cry2, Cry4C/4D, Cry6A, Cry10, Cry11, Cry34, Cry35, Cyt1/2). Four of the isolates (N6Bss, 8a3, R1 and A2B) harboured all six of the examined insecticidal genes (cry1, cry2, cry4, cry10, cry11 and cyt2), which are known to produce Dipteran-specific delta-endotoxins. Nevertheless, results suggested minimal correlations between the examined characteristics of the B.thuringiensis isolates. Bioefficacy analysis showed varying degrees of toxicity, with three B. thuringiensis isolates (A10C, R2 and A2B) exhibited good larvicidal properties. Generated LC50 and LC95 values of all three isolates against Ae. albopictus and Ae. aegypti up to 48 hours’ post-treatment were below 0.3 mg/mL and 0.5 mg/mL, respectively. Sublethal evaluations of the three best isolates saw inversely impacted life parameters on treated Aedes spp. larvae, such as decreases in adult emergence, gender ratio, fecundity, fertility, and adult wing sizes; with R2 giving the highest adverse sublethal effects. Findings in this study support the idea that distribution of B. thuringiensis with combinations of insecticidal cry/cyt genes is associated with presence of targeted insects and may serve as potential broad-spectrum biopesticides to be incorporated as part of local vector control management programmes. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/14878 | |
| dc.language.iso | en | en_US |
| dc.publisher | Universiti Sains Malaysia | en_US |
| dc.subject | Dengue | en_US |
| dc.title | Isolation, Characterisation And Bioefficacy Analysis Of Bacillus Thuringiensis (Bt) Strains Against Dengue Vectors | en_US |
| dc.type | Thesis | en_US |
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