An experiment was conducted under laboratory condition to evaluate the
insecticidal activity of three newly compounds extracted from wastes from natural
origin, Cyano acetyl urea (CAU), Benzimidazolyl acetyl urea (BAU) from urea and
Cyano acetyl hydrolyzate (CAH) from rice straw, on cotton leaf worm (Spodoptera
littoralis) through exposure of fourth instar larvae to castor bean leaves which
immersed in different concentrations from tested compounds. In addition, the
morphogenic abnormalities were recorded.
The other objective of this study is to evaluate the potential of the random
amplified polymorphic DNA (RAPD) assay for the detection of genetic
polymorphism between control and treated S. littoralis larvae, which have been
exposed to the tested compounds at both LC25 and LC70. Five primers namely: OP-01,
OP-02, OP-03, OP-04, and OP-05 were used in this study.
The present findings clear that, LC25 estimates of fourth instar larvae ranged
from 0.092 to 0.154 % of (CAU), 0.191 to 0.225 % of (BAU) and 0.009 to 0.021 %
of (CAH) while, LC70 estimates of fourth instar larvae ranged from 1.289 to 2.009 %
of (CAU), 1.445 to 2.159 % of (BAU) and 0.339 to 0.627 % of (CAH).
In addition, five primers OP-01, OP-02, OP-03, OP-04, and OP-05 generated a
maximum of 26, 24, 20, 13 and 23 bands, respectively. RAPD profiles generated by
these primers revealed differences between control and treated samples with visible
changes in number and size of amplified DNA fragments. Polymorphism ranged from
44.4 to 100% as screened by the five primers among all samples. Taking all data
together, higher polymorphism was recorded at LC70 (77.8, 84.4, and 86.4%)
comparing corresponding values at LC25 (69.6, 80.3, and 79.4%) for larvae treated
with CAU, BAU and CAH, respectively. Based on LC70, the highest polymorphism
(86.4%) was observed in those treated with CAH comparing those either treated with
CAU (77.8%) or with BAU (84.4%). Definitely, RAPD data confirmed the
susceptibility test as well as the morphological study, and suggest that DNA damage
and the possible occurred mutations may appear to be the main factor influencing the
evident polymorphism between control and treated larvae.