Genetics of resistance to Cry1C toxin from Bacillus thuringiensis in Spodoptera litura (Fab.)

The present study was undertaken to determine the genetics of Cry1C resistance in Spodoptera litura. Selection of S. litura (Fab.) with Cry1C was done for eight generations to develop resistance. Reciprocal crosses between resistant and susceptible populations were made to understand the population genetics of Cry1C resistance in S. litura. Generation wise selection with Cry1C was evaluated for resistance development in S. litura. The LC₅₀ of Cry1C was 0.14 µg/cm² for the first selected generation and it increased to 23.98 µg/cm² after eight selected generations, which is a 285.47-fold increase in resistance compared with the susceptible strain. The estimated realized heritability (h²) after eight generations of selection with Cry1C insecticidal protein was 0.44. The number of generations required for the tenfold increase in LC₅₀ (1/R) was estimated to be 3.33. Response to Cry1C selection in S. litura was 0.30, the estimated selection differential was 0.69 and the pheonotypic standard deviation (dP) was 0.24. Reciprocal crosses between Cry1C resistant and susceptible strain of S. litura showed autosomal resistance.