Transgenic Bacillus thuringiensis (Bt) cotton (Gossypium hirsutum) allomone response to cotton aphid, Aphis gossypii, in a closed-dynamics CO(2) chamber (CDCC)

Allocation of allomones of transgenic Bacillus thuringiensis Gossypium hirsutum (Bt cotton) (cv. GK-12) and non-Bt-transgenic cotton (cv. Simian-3) grown in elevated CO₂ in response to infestation by cotton aphid, Aphis gossypii Glover, was studied in a closed-dynamics CO₂ chamber. Significant increases in foliar condensed tannin and carbon/nitrogen ratio for GK-12 and Simian-3 were observed in elevated CO₂ relative to ambient CO_2, as partially supported by the carbon nutrient balance hypothesis, owing to limiting nitrogen and excess carbon in cotton plants in response to elevated CO₂. The CO₂ level significantly influenced the foliar nutrients and allomones in the cotton plants. Aphid infestation significantly affected foliar nitrogen and allomone compounds in the cotton plants. Allomone allocation patterns in transgenic Bt cotton infested by A. gossypii may have broader implications across a range of plant and herbivorous insects as CO₂ continues to rise. Gang Wu and Fa Jun Chen contributed equally to this work.