| Abstrakt: |
In this study, sublethal effects, toxicity of Bacillus thuringiensis δ-endotoxin (Cry1Ac) on development, reproductive behaviour, and life table characteristics of the tobacco cutworm, Spodoptera litura (S. litura) were assessed by leaf dip bioassay method. The SDS-PAGE of the B.t. endotoxin revealed a single band with 65 kDa size confirmed the presence of activated Cry1Ac protein. The bioassay of Cry1Ac toxin to S. litura was recorded and the LC25, LC50 and LC75 values were 5.78, 22.67 and 88.83 µg/mL, respectively. The results indicated that the biological and life table characters were significantly affected in dose-dependent manner. The influence on life table also revealed higher net reproductive rates (Ro), intrinsic rate of increase (r), finite rate of increase (λ), mean fecundity (F) and lower mean generation time (T) in control (183.8 females/generation, 0.157/day, 1.170/ day, 420.80 eggs/female and 33.05 days, respectively) followed by LC25 (161.9 females/generation, 0.145/day, 1.156/ day, 375.20 eggs/female and 34.25 days, respectively). Similarly, LC50 of Cry1Ac toxin (132 females/generation, 0.123/day, 1.131/ day, 334.00 eggs/female and 39.5 days, respectively). On the contrary, the lower net reproductive rates (Ro), intrinsic rate of increase (r), finite rate of increase (λ), mean fecundity (F) and higher mean generation time (T) were recorded in LC75 of Cry1Ac toxin (103.1 females/generation, 0.100/day, 1.105/day, 313.25 eggs/female and 46.09 days, respectively). Furthermore, the unhealthy larvae with longer developmental time may make them more susceptible to natural enemies and entomopathogens which indeed decrease the population growth and density of S. litura. [ABSTRACT FROM AUTHOR] |
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