Susceptibility of Two Populations of Leucinodes Orbonalis Guen. to Cry1 AC Toxin

Laboratory experiments were conducted at Indian Institute of Vegetable Research, Varanasi to standardise the artificial diet for rearing and conducting bioassay on the Cry 1 Ac-incorporated diets of Leucinodes orbonalis. Drying and disinfection of black gram-based diet in the feeding tubes improved the larval survival and adult emergence which was comparable to the brinjal fruits. There was no significant difference in mortality of BSFB larvae among the substrates i.e., brinjal fruit, brinjal flower and artificial diet. Irrespective of the substrates the presence of Cry1 Ac in transgenic plant and diet recorded significantly higher mortality over the normal plant and diet. Although Varanasi population was slightly more susceptible than Mirzapur population, the difference was non-significant. The LC₅₀ value of larvae collected from Mirzapur was also marginally more than the Varanasi population. In general the laboratory population was more susceptible to Bt protein than the field population. Although variation in susceptibility to Cry1 Ac was observed between the two populations (Varanasi and Mirzapur) of L. orbonalis, the magnitude of the difference was small.