EFFECTS OF PINK BOLLWORM RESISTANCE TO TRANSGENIC COTTON ON MOTH MATING, OVIPOSITION AND LARVAL PROGENY DEVELOPMENT, 2006

This experiment was conducted to determine the effects of the PBW selection for Bt resistance on adult oviposition, mating, egg hatch and survival of our Bt (Bt4R) resistant strain. We separated male and female fourth instar larvae reared on artificial diet containing Bt Cry1 toxic protein (10 μg/ml). Larvae were held in cylindrical waxed cardboard cages until pupal and adult emergence. Five Bt4R females were paired with 5 WCRL males, 5 WCRL females were paired with 5 Bt4R males and equal numbers of pairs of each strain paired and placed when 1 to 3 days old in mating-oviposition cages with oviposition substrates and sugar solution vials for adult food. Containers with moth pairs and oviposition substrates were held in 26.7°C cabinets (14:10, L:D photoperiod). Checks were WCRL larvae reared on artificial diet without Cry1Ac toxin and treated similarly in all other respects. The study was replicated 5 times in a RCB design. Oviposition substrates with the eggs from each of the reciprocal-cross matings of resistant and non-resistant moth pairs were collected after 10 days and examined and substrate pieces containing ~ 1⁄2 of the eggs were placed in 6.5 cm tall × 6.5 cm diameter cylindrical containers with ~ 2 gm of either artificial diet alone or artificial diet containing 10 μg Cry1Ac/ml. Adult females were collected, dissected and examined for the presence of spermataphores to verify mating. Cups with larvae and diet were returned to the 26.7°C cabinets in a RCB design for 21 days. Numbers of larval progeny and instar development on the artificial diet alone and artificial diet containing 10 μg/ml Cry1Ac protein were recorded. The study was also replicated 5 times. Data were analyzed using ANOVA for comparisons between moth strains for differences in immature larval survival, oviposition, egg hatch and larval mortalities. Significant F ratios were accepted at probabilities (P) of ≤ 0.05. Mortality percentages were corrected for check mortalities using Abbott’s formula. All percentages were arcsine transformed before statistical analysis. Means were separated using the method of Least Significant Differences at P levels of ≤ 0.05.