| Abstract: |
Bacillus thuringiensis, is a gram positive bacteria known for it’s widely usage as bioinsecticide to control insect pests represent a threat for agriculture. Five local isolates of Bacillus thuringiensis have been isolated from soil samples collected from different areas in Sharkia governorate, Egypt. Morphological, biochemical and phenotypic characterization analyses and molecular biology methods were employed to identify these isolates. When crystal morphology of bacterial isolates was examined, isolates were found to produce distinct crystal proteins which were very similar to crystal proteins produced normally by Bacillus thuringiensis. The presence of different cry genes was determined in five isolates. Two cry genes, cry3 and cry8 could be detected in two isolates in BTRW2 and BTRW4; at least one cry gene could be detected. The most predominant crystal protein gene in the isolates tested was of cry3 group. from all five local isolate BTRW1 only showed vip1A specific (2.4kp). Moreover, when identification was performed using 16S rRNA gene sequencing, revealed that the isolates are Bacillus thuringiensis. Protein SDS-PAGE analysis of vegetative and sporulated cells of the five isolates showed that the protein banding pattern of the five isolates was different from each other. Insecticidal activity of the novel isolates have been tested against the red palm weevil (RPW), Rhynchophorus ferrugineus. The LC50s of the local isolates BTRW1, BTRW2, BTRW3, BTRW4 and BTRW5 against RPW have been determined and were 0.062, 0.252, 0.178, 0.060 and 0.061 µg/ml, respectively, In the same time, no insecticidal activity have been detected for these isolates against cotton leaf worm. Gene transfer among Bt bacteria can occur. Upon using conjugation as a mechanism of gene transfer to transfer cry gene into a different species such as (B. cereus).
|
|
|