Resistance selection of Plutella xylostella by Cry1Ac toxin and Bt formulation and biological fitness of the resistant populations

Two diamondback moth populations, DBM.1Ac-R30 and DBM.Bt-R46, with resistant ratios of 24.36 to Cry1Ac and 38.16 to Bt were obtained after 30 and 46 generations of selection with Cry1Ac toxin and Bt formulation respectively in the laboratory. The basic biological properties, such as developmental, reproductive and survival characteristics, of the above two resistant populations and their unselected parent population DBM.Bt-S were studied. The results showed the DBM.1Ac-R30 and DBM.Bt-R46 had a fitness value of 0.75 and 0.65 relative to the susceptible DBM.Bt-S population, respectively. These resistant populations showed reproductive disadvantages, including lower number of eggs laid and hatching rate, prolonged larval period, lower sex ratio (♀∶♂), and shorter life-span and less number of female adults compared with the susceptible population.