Title: Enhancement of Insecticidal Protein Activity by Spores of Bacillus thuringiensis against the Diamondback Moth, Plutella xylostella, Developing Resistance to Insecticidal Protein.
Abstract: The diamondback moth, Plutella xylostella that was 2,400-fold resistant to insecticidal proteins of Bacillus thuringiensis serovar kurstaki HD-1 was selected from the susceptible strain. Against the resistant strain, spore combination enhanced the activity of kurstaki HD-1 insecticidal proteins 8,800-fold, which was significantly higher than the enhancement (160-fold) against the susceptible strain. When recombinant Cry1Aa, Cry1Ab or Cry1Ac toxin was fed to the susceptible strain, the spore combination enhanced the activity only 3 to 8-fold. Against the resistant strain, however, the spore combinations with recombinant proteins enhanced the activities more than 900-fold. These results show that the spore combination with insecticidal proteins is also effective to control the diamondback moth larvae that developed resistance to the insecticidal proteins of B. thuringiensis.