Effect of NaCl-Stressed Bt Cotton on the Feeding Behaviors and Nutritional Parameters of Helicoverpa armigera

Saline-alkali soil is an arable land resource on which transgenic Bt cotton has been planted on a large scale in accordance with food security strategies, but there are concerns about the insecticidal effects of Bt cotton on target insect pests. In this study, a Bacillus thuringiensis (Bt) cotton variety, GK19, and its nontransgenic parent variety, Simian-3, were used as experimental materials to study the effect of the expression of exogenous insecticidal proteins in Bt cotton under NaCl stress on the feeding behavior and nutritional parameters of Helicoverpa armigera. The results showed that the expression of exogenous insecticidal proteins in GK19 was significantly inhibited under NaCl stress. However, on GK19 Bt cotton, the feeding, crawling, resting and spinning down of the 5th instar H. armigera larvae, as well as the food consumption and feces amount of these larvae, did not markedly differ under different NaCl concentrations. In contrast, the mean relative growth rate (MRGR), relative growth rate (RGR), approximate digestibility (AD), efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD) of the larvae decreased markedly in response to NaCl stress. Under the same concentration of NaCl, the nutritional parameters of the bollworm larvae on GK19 Bt cotton or Simian-3 nontransgenic cotton were different. However, the interaction between salt stress and cotton variety had no significant effect on the feeding behavior or nutritional parameters of H. armigera larvae. These results may provide a scientific basis for determining the effect of exogenous insecticidal protein expression in Bt cotton under NaCl stress on H. armigera and can therefore be useful for the effective application of Bt cotton in saline-alkali soils to prevent and control H. armigera.