Lack of cross-resistance to Cry19A from Bacillus thuringiensis subsp jegathesan in Culex quinquefasciatus (Diptera : Culicidae) resistant to cry toxins from Bacillus thuringiensis subsp israelensis

Culex quinquefasciatus mosquitoes with high levels of resistance to single or multiple toxins from Bacillus thuringiensis subsp. israelensis were test ed for cross-resistance to the Bacillus thuringiensis subsp. jegathesan pol ypeptide Cry19A. No cross-resistance was detected in mosquitoes that had be en selected with the Cry11A, Cry4A and Cry4B, or Cry4A, Cry4B, Cry11A, and CytA toxins. A low but statistically significant level of cross-resistance, three to fourfold, was detected in the colony selected with Cry4A, Cry4B, and Cry11A. This cross-resistance was similar to that previously detected w ith B. thuringiensis subsp. jegathesan in the same colony. These data help explain the toxicity of B. thuringiensis subsp. jegathesan against the resi stant colonies and indicate that the Cry19A polypeptide might be useful in managing resistance and/or as a component of synthetic combinations of mosq uitocidal toxins.