Low Bt toxin concentration in seeds results in low insecticidal efficacy in transgenic Bt cotton. In order to improve the insecticidal efficacy of seeds, two treatments with different amino acid combinations (5 amino acids comprising aspartic acid, glutamic acid, proline, methionine, and arginine; and 21 amino acids) were applied to two Bt cotton cultivars at peak boll stages in 2021 and 2022. The results showed that the amino acid treatments enhanced the seeds’ Bt toxin concentration by 13.5–34.2% compared with the untreated control in a two-year study. However, the difference for the Bt toxin was not significant between the two amino acid treatments. In the seeds, Bt toxin levels correlated positively with amino acid and soluble protein contents, as well as Glutamic-Pyruvic Transaminase (GPT) and Glutamate Oxaloacetate Transaminase (GOT) activities. Conversely, negative correlations were observed between the Bt toxin and the activities of protease and peptidase. Compared with the control, hazard boll rates were also reduced following application of the two amino acid combinations, while no difference was observed between the two amino acid treatments. Because the two treatments performed similarly, these results suggest that applying a simpler combination of five amino acids is an effective and efficient strategy for enhancing the insecticidal efficacy of cotton seeds.
Ji et al. (Mon,) studied this question.