Insecticidal activity and receptor binding properties of Bacillus thuringiensis toxins to yellow and striped rice stem borers (Sciropophaga incertulas and Chilo suppresalis, respectively) were investigated. Yellow stem borer (YSB) was susceptible to Cry1Aa, Cry1Ac, Cry2A, and Cry1C toxins with similar toxicities. To striped stem borer (SSB), Cry1Ac, Cry2A, and Cry1C were more toxic than Cry1Aa ...

The Bacillus thuringiensis subsp. israelensis cytolytic protein Cyt1Aa was found to be toxic to an insecticide-susceptible laboratory population of Plutella xylostella. Cry1Ac-resistant populations of P. xylostella showed various degrees of resistance to Cyt1Aa. Cyt1Aa/Cry1Ac mixtures showed a marked level of synergism in the Cry1Ac-resistant populations.

Thirteen commercial varieties of transgenic Cry1Ac Bacillus thuringiensis Berliner (Bt) cotton were examined across two sites in 2000 for potential factors that impact endotoxin expression. In all cases, two varieties (NuCOTN 33B and DP 458B/RR, Delta & Pineland Co., Scott, MS) expressed more Cry1Ac than the other 11 varieties in various plant structures. These two varieties share the same pare...

Soybean tissue and arthropods were collected in Bt soybean fields in China at different times during the growing season to investigate the exposure of arthropods to the plant-produced Cry1Ac toxin and the transmission of the toxin within the food web. Samples from 52 arthropod species/taxa belonging to 42 families in 10 orders were analysed for their Cry1Ac content using enzyme-linked immunosor...

Two colonies of Asian corn borer, Ostrinia furnacalis (Guenée), artificially selected from a Bt-susceptible colony (ACB-BtS) for resistance to Cry1Ab (ACB-AbR) and Cry1Ac (ACB-AcR) toxins, were used to analyze inheritance patterns of resistance to Cry1 toxins. ACB-AbR and ACB-AcR evolved significant levels of resistance, with resistance ratios (RR) of 39-fold and 78.8-fold to Cry1Ab and Cry1Ac,...

Binding of the Bacillus thuringiensis Cry1Ac toxin to specific receptors in the midgut brush border membrane is required for toxicity. Alteration of these receptors is the most reported mechanism of resistance. We used a proteomic approach to identify Cry1Ac binding proteins from intestinal brush border membrane (BBM) prepared from Heliothis virescens larvae. Cry1Ac binding BBM proteins were de...

Transgenic crops producing Bacillus thuringiensis (Bt) toxins have been planted widely to control insect pests, yet evolution of resistance by the pests can reduce the benefits of this approach. Recessive mutations in the extracellular domain of toxin-binding cadherin proteins that confer resistance to Bt toxin Cry1Ac by disrupting toxin binding have been reported previously in three major lepi...

A synthetic laboratory population of the diamondback moth, Plutella xylostella (L.), was used to test the F2 screen developed for detecting the frequency of rare resistance alleles to Cry1Ac and Cry1C toxins of Bacillus thuringiensis (Bt). Of the 120 single-pair matings set up, 106 produced enough F2 families for screening of Cry1Ac or Cry1C resistance alleles using both transgenic broccoli and...

To delay evolution of pest resistance to transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt), the "pyramid" strategy uses plants that produce two or more toxins that kill the same pest. We conducted laboratory diet experiments with the cotton bollworm, Helicoverpa armigera, to evaluate cross-resistance and interactions between two toxins in pyramided Bt cotton (Cry...

Insecticidal proteins Cry1Ac and Cry2Ac7 from the bacterium Bacillus thuringiensis (Bt) belong to the three-domain family of Bt toxins. Commercial transgenic soybean hybrids produce Cry1Ac to control the larvae of the soybean looper (Chrysodeixis includens) and the velvet bean caterpillar (Anticarsia gemmatalis). The specificity of Cry1Ac is determined by loops extending from domain II and regi...