Isolation And Characterization Of Bacillus Thuringiensis And Its Larvicidal Activity Against Mosquito

Application of chemical insecticides poses a wide range of problems in the environment. Theyare non specific and are implicated as carcinogens hence the need to search for an eco-friendlybiological control agent such as the use of Bacillus thuringiensis habouring insecticidal crystals.In this study, Bacillus thuringiensis were isolated from different soil types in Zaria. The 12isolates from these obtained from different soil types were screened for the presence of cry geneby PCR using primers specific for cry2 and cry4 (diptera-active cry genes). Of the 12 isolates, 1isolate had only cry2 gene, 4 isolates had cry4 gene, 1 isolate had both of the genes while 6isolates had none of the two genes. Bioassay to assess the insecticidal activity of the isolates wascarried out using Culex quinquefasciatus and Aedes aegypti larvae using 3 differentconcentrations of spore crystal mixture (100, 75 and 50 ppm) alongside one control. In each case,10 larvae of Cx. quinquefasciatus and A. aegypti were exposed to spore crystal mixture intriplicates for both. The isolates differ greatly in their larvicidal activity against the larvae of Cx.quinquefasciatus and A. aegyti. The mortality of Cx. quinquefasciatus larvae when exposed to100ppm concentration of the isolates’ spore crystal mixture ranged between 33.33% and 96.00%while the range of mortality for A. aegyti was between 40.00% and 100.00%. The concentrationsof the spore crystal mixture which kill 50% of the exposed populations in standard bioassays(LC50) were determined by probit analyses. The LC50 using Culex quinquefasciatus was between135.95ppm and 37.48ppm while it was between 118.03ppm and 55.79ppm for Aedes aegypti.The results of this research shows that the isolates habouring the diptera-active cry gene from thesoils in Zaria can serve as biocontrol agent for the control of mosquito by targeting their larvaestage hence controlling the diseases they spread.

Get Full Work

Report copyright infringement or plagiarism