University of Khartoum

Characterization of Entomopathogenic Strains of Bacillus thuringiensis from Sudan

Characterization of Entomopathogenic Strains of Bacillus thuringiensis from Sudan

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Title: Characterization of Entomopathogenic Strains of Bacillus thuringiensis from Sudan
Author: Eltayeb Gorashi, Naiema
Abstract: The objectives of this research were to characterize soil isolates of Bacillus thuringiensis and to examine their potential in controlling insects of agricultural and medical importance. From a great number of Bacillus isolates obtained from soil and grain stores, 39 proved to be Bacillus thuringiensis (Bt) as confirmed by the presence of spores and protein crystals as well as by biochemical tests. These isolates were used to infect the larvae of three insects of agricultural and medical importance. These insects belonged to three different orders. The insects tested were: the red flour beetle (Tribolium castaneum; Coleoptera), the greater wax moth (Galleria mellonella; Lepidoptera) and the mosquito (Culex quinquefasciatus; Diptera). Approximately 59% of the 39 Bt isolates were found pathogenic (mortality ≥50%) to the red flour beetle with mortality reaching 85% with some isolates. About 58.9% of the Bt isolates were pathogenic to the greater wax moth, with some isolates causing 81% mortality in 10 days. With respect to mosquito, 69% of the Bt isolates were pathogenic in 42 hours only, some causing mortalities between 90 and 95%. About 23% of the isolates were pathogenic to all the three insects, 18% were pathogenic to the mosquito and the red flour beetle, 13% pathogenic to both the red flour beetle and the greater wax moth, and 15% were pathogenic to both the mosquito and the greater wax moth. Five percent of the isolates were not pathogenic to any of the test insects, 5% were specific to the red flour beetle only, 8% showed activity towards the greater wax moth only and 13% affected only the mosquito. The maximum reduction in the amount of food consumed by the treated larvae was 86.9% and recorded when the larvae of greater wax moth were exposed to isolate Po-2. Regression analysis revealed differences in the lethal times between different isolates towards the three insects, where mosquito was proved the most sensitive (Lt50 29.38 hours to isolate Om-5).
Description: 150 Pages
URI: http://khartoumspace.uofk.edu/handle/123456789/13446
Date: 2015-06-17


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