Efficiency of Using Some New Insecticides against Cotton Leaf Worm (Spodopteralittoralis) Based on Biochemical and Molecular Markers

Heidi A. Ali , Ahmed M. Kordy, Ahmed E. Khaled, Nabeill A. Hassan, Nader R. Abdelsalam

Bioassays were carried out for evaluating the toxicity of different insecticides against the susceptible strain of cotton Leafworm, Spodoptera littoralis (Boisd.). Toxicity data based on LC50 values indicated that the proclam® is more toxic insecticide against the laboratory strain, while, the OP syclon®was less toxic. Esterase isozymes exhibited a wide range of variability among the pupae and larvae. Two common bands were detected among all samples in pupae and larvae. Proclam showed one band in pupae (Es.C2) compared with other treatments and in larvae detected one band in (Es.C3) and detecte the highest band number (6 bands) comparing with other insectcides. The results of biochemical analysis showed that there is arelationship between the resistance to insecticide and the increase of enzyme activity such as esterase enzyme. Five out of ten oligonucleotide primers (50%) used in the RAPD analysis gave unique markers. Out of the five primers, two detected single unique markers (OPA-02 and OPA-15), two gave two markers (OPA-05 and opc-02), and one yielded three unique markers (OPC-12).Additionally, compared with the control worms, cotton leaf worm exposed to insecticides recorded the emergence of 7 new fragments from 98 total fragments. So, the total number of fragments which disappeared in response to both treatments was 98 fragments. Exposure to insecticides at all concentrations revealed the increase or decrease the number of amplified polymorphic DNA and increased gene expression in comparison to control cotton leaf worm.