ABSTRACTBacillus thuringiensisis an important source of insect resistance traits in commercial crops. In an effort to prolongB. thuringiensistrait durability, insect resistance management programs often include combinations of insecticidal proteins that are not cross resistant or have demonstrable differences in their site of action as a means to mitigate the development of resistant insect populations. In this report, we describe the activity spectrum of a novelB. thuringiensisCry protein, Cry1Bh1, against several lepidopteran pests, including laboratory-selectedB. thuringiensis-resistant strains ofOstrinia nubilalisandHeliothis virescensand progeny of field-evolvedB. thuringiensis-resistant strains ofPlutella xylostellaandSpodoptera frugiperda. Cry1Bh1 is active against susceptible andB. thuringiensis-resistant colonies ofO. nubilalis,P. xylostella, andH. virescensin laboratory diet-based assays, implying a lack of cross-resistance in these insects. However, Cry1Bh1 is not active against susceptible or Cry1F-resistantS. frugiperda. Further, Cry1Bh1 does not compete with Cry1Fa or Cry1Ab forO. nubilalismidgut brush border membrane binding sites. Cry1Bh1-expressing corn, while not completely resistant to insect damage, provided significantly better leaf protection against Cry1Fa-resistantO. nubilalisthan did Cry1Fa-expressing hybrid corn. The lack of cross-resistance with Cry1Ab and Cry1Fa along with independent membrane binding sites inO. nubilalismakes Cry1Bh1 a candidate to further optimize for in-plant resistance to this pest.
Shared Midgut Binding Sites for Cry1A.105, Cry1Aa, Cry1Ab, Cry1Ac and Cry1Fa Proteins from Bacillus thuringiensis in Two Important Corn Pests, Ostrinia nubilalis and Spodoptera frugiperda