A biochemical approach to potentiate the activity ofBacillus thuringiensis against corn borers |
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Authors: | M Hafez H S Salama A El-Moursy A Abdel Rahman |
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Institution: | (1) Faculty of Science, Cairo University, Dokki, Cairo;(2) National Research Centre, Tahrir St., Dokki, Cairo, Egypt |
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Abstract: | Due to the fact that the persistence ofBacillus thuringiensis (B.t.) is very short in the field as affected by exposure to ultraviolet radiation, some biochemical approaches have been adopted
in an attempt to increase potentiation of the pathogen against the two lepidopterous corn borers,Chilo agamemnon andOstrinia nubilalis. These approaches were based on the incorporation of some selected non-toxic chemical compounds with different modes of action
with the endotoxin ofB.t. fed to the larvae and thus resulting in its potentiation.
Among the compounds tested, some representatives of inorganic salts, organic acids, protein and lipid solubilizing agents,
amino acids and amides showed an obvious potentiation to the endotoxin activity against the target insects. Inorganic salts,
such as, calcium oxide, calcium carbonate, zinc sulphate and potassium carbonate at 0.1% potentiated the activity of the product
Dipel 2X (B.t. var.kurstaki) against the two tested species in varying degrees. With regard to protein solubilzing agents, urea, sodium thioglycollate
and EDTA enhanced the potency ofB.t. againstO. nubilalis with a fold increase of 1.4–2.3. The lipid emulsifying agent Tween 80 (0.5%), caused 1.3 fold increase in the potency ofB.t. With respect toC. agamemnon, sodium thioglycollate and EDTA (0.1%) were effective in potentiating the activity ofB.t. with fold increase of 3.1 and 1.2, respectively, while urea caused a decrease in the potency ofB.t as compared with the control. The lipid emulsifying agent Tween 80 (0.5%) caused 1.3 fold increase in the potency ofB.t. The potentiating effect of aromatic compounds is not obvious with respect to the tested insect species. With amino acids
and amides, it appears that some of the tested compounds enhanced the potency ofB.t. against the tested insect species but in varying degrees. The mode of action of the tested compounds has been discussed in
the light of the results obtained. |
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