Growth and development of Bacillus thuringiensis Cry1Ab-susceptible and Cry1Ab-resistant sugarcane borer on diet and conventional maize plants

摘要

The sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), is a dominant maize borer pest and a major target of Bacillus thuringiensis (Bt)-maize in Louisiana and the Gulf Coast area of Texas (USA). Growth and development of D. saccharalis on non-toxic diet, diet treated with three low concentrations (0.01, 0.05, and 0.1 og gp#) of Cry1Ab toxin, and on non-Bt maize plants were compared for five insect genotypes: a Bt-susceptible strain (BT-SS), a Cry1Ab-resistant strain (BT-RR), a back-crossed and re-selected resistant strain (BT-R'R'), and two F progeny of the BT-SS and BT-R'R' strains. Fitness of the five genotypes was examined by infesting neonates on diet with/without Cry1Ab toxin in the laboratory and on intact non-Bt maize plants in the greenhouse. Biological parameters measured were neonate-to-pupa development time and pupation rate, larval survival, larval and pupal weight, and sex ratio. Larvae of BT-SS and BT-R'R' on non-toxic diet and non-Bt maize plants grew normally and there were no significant differences between the two strains in all measured parameters, suggesting a lack-of-fitness cost of the Cry1Ab resistance in D. saccharalis. Except for the development time on non-Bt diet, all other parameters on both non-Bt diet and non-Bt maize plants were similar among the five genotypes. Larval development of BT-SS was significantly affected on diet treated with Cry1Ab toxin at 0.05 and 0.1 og gp#, whereas the effect to BT-RR and BT-R'R' was not significant. Pupal weight and sex ratio reared on Cry1Ab-diet were similar and there were no significant differences among the five genotypes. Neonate-to-pupation rate decreased as Cry1Ab concentrations increased but the decrease was more significant for BT-SS than for the other four genotypes. The lack-of-fitness costs of Bt resistance in D. saccharalis imply a greater challenge in managing Bt resistance for this maize borer species.