D3375: Bacillus thuringiensis-derived pesticidal proteins toxic to the whitefly

The sweet potato whitefly, Bemisia tabaci, is a highly destructive, invasive agricultural pest. Damage results from direct feeding, mold associated with honeydew excretion, and the transmission of numerous plant viruses impacting a wide range of host plants including vegetables, field and ornamental crops. Whitefly management entails extensive use of chemical pesticides, particularly neonicotinoids, and insecticide resistance is now widespread. While pesticidal proteins from Bacillus thuringiensis (Bt) and other entomopathogenic bacteria potentially provide environmentally friendly alternatives to chemical pesticides, only one protein was known to be active against B. tabaci. Here we report on the toxicity of 11 Bt-derived pesticidal proteins from several different structural classes against B. tabaci Middle East-Asian Minor 1 (MEAM1). These proteins were either expressed in Bt and purified from crystals, or expressed in Escherichia coli and purified from inclusion bodies or by His-tag affinity chromatography. The toxicity of purified proteins was first assessed by feeding adult whiteflies on a single dose followed by lethal concentration (LC₅₀) determination for proteins with significant mortality relative to the buffer control. The proteins Tpp78Aa1, Tpp78Ba1, and Cry1Ca were toxic to B. tabaci with LC₅₀ values of 99, 96, and 351 µg/mL, respectively. These proteins provide valuable tools to mitigate losses associated with B. tabaci and the numerous plant viruses transmitted by this insect.