Cytochrome P450 Isoforms Transcriptional, Larval Growth and Development Responses to Host Allelochemicals in the Generalist Herbivore, Helicoverpa armigera (Hubner) (Lepidoptera:Noctuidae)

Helicoverpa armigera (Hubner) is a polyphagous pest causing severe yield loss in many important crops. Host plants produce allelochemicals to deter insect pests and in response, insects deploy cytochrome P450 monooxygenases (P450s) to detoxify allelochemicals. Understanding the response of P450s to allelochemical exposure is key to effective pest management. We studied the response of seven H. armigera P450 isoforms to different concentrations of three allelochemi-cals (gossypol, tomatine and xanthotoxin) and their effects on insect growth and survival. Allelochemicals strongly induced overexpression of some P450s. CYP6AE14 exhibited the highest overexpression in gossypol treatment. CYP6AE14 and CYP6B7 exhibited higher overexpression in xanthotoxin treatment and CYP6B7 showed the highest overexpression in tomatine treatment. Overall, CYP6AE14 and CYP6B7 were induced by all three allelochemicals. Higher (0.5 and 1.0 μg) concentrations of allelochemicals caused significant larval growth retardation. Interestingly, gossypol showed a hormetic effect, i.e. larval weight was approximately 10% higher at lower (0.025 μg) concentration. Highest larval mortality (53%) was observed in tomatine treatment. These findings would help in identifying suitable P450 isoforms in the management of H. armigera.