Chen Dehua

Effect on Stresses of 18℃ and Different Relative Humidities on Bt Protein Expression at Squaring Stage in Bt Cotton

The objective of this study was to investigate the effect of stresses of 18℃ and different relative humidities on the leaf resistance to the insect at squaring stage in Bt cotton. The two conventional cultivars (DP410B and Sikang 1) and two hybrids (Daiza 1 and Sikang 3) from the US and China, respectively, were used. The potted cotton plants were stressed at 18℃ and different relative humidities (90%, 70%, and 50%) for 6 hours and 48 hours, respectively, then we determined leaf Bt protein contents. The results showed that the short period (6 hours) stress of 18℃ and different relative humidities obviously had no effect on the leaf Bt protein contents. but the leaf Bt protein contents sharply reduced in the two Bt conventional cultivars after the longer period (48 hours) stress of 18℃ and different relative humidities compared with the control, with the reduction from 6.8% to 7.2%. The leaf Bt protein content of hybrid Sikang 3 markedly decreased while that of hybrid Daiza 1 remained unchanged. There was no difference in the effect between the high relative humidity and low relative humidity at 18℃, so the low temperature duration may affect the Bt cotton resistance to insect at squaring stage, which is closely related to cultivars.