Biological traits associated with Cry1Ac resistance in <em>Helicoverpa</em> <em>armigera</em> (Lepidoptera: Noctuidae)

722-727The cotton bollworm, Helicoverpa armigera (Hübner) is an important cotton pest worldwide, and it causes losses up to 30% of the total cotton production in India. Though the insecticidal crystal (Cry) proteins produced by Bacillus thuringiensis (Bt) have been effective against lepidopteran pests, evolution of resistance has become an issue of concern. Study of fitness costs associated with resistance to Bt Cry toxins gives an insight to resistance evolution and helps in effective resistance management. Here, we studied a number of biological traits of resistant and susceptible population of Helicoverpa armigera on Cry toxin treated and untreated diet to understand the association between Cry1Ac resistant and biological traits. Isofemale lines were obtained by single pairing of field collected H. armigera population. The F2 of the isofemale line were assayed at concentration of 1 and 10 µg of Cry1Ac/g of diet. The line which showed highest survival percentage was the resistant line DNDT-R and the line which showed the lowest survival percentage was the susceptible line M4-S. Biological traits were studied by conducting crosses and backcrosses of the resistant and susceptible line. The F1 progeny and resistant parent showed significantly better performance than the susceptible parent in various biological parameters. The per cent pupation and adult emergence were higher in F1 and F2 generations than the susceptible parent and also between resistant and F1 on both treated and untreated diet. This finding is important to know the fitness cost expressed by resistant population over susceptible population so as to delay resistance development