Effects of temperature, water content and pH on degradation of Cry1Ab protein released from Bt corn straw in soil

We investigated the effects of soil temperature (15 °C, 25 °C, 35 °C), water content (20%, 33%, 50%) and pH (4.5, 7.0, 9.0) on the degradation of Cry1Ab protein released from the straw of Bt corn varieties 34B24 and 1246 × 1482 both expressing Cry1Ab protein. Our results showed that Cry1Ab protein released from both 34B24 and 1246 × 1482 straw was degraded in a similar way in all treatments, which demonstrated a rapid decline in the early stage but a slow decline in the middle and late stages. In the late stage (180 days after the experiment commenced) 0.03%–1.51% and 0.02%–0.91% of initial Cry1Ab protein released from 34B24 and 1246 × 1482 straw was detected in soil. In addition, degradation dynamics of Cry1Ab protein under different environmental conditions was well described by the shift-log model. DT50 of Cry1Ab protein released from 34B24 and 1246 × 1482 straw was 0.97–9.97 d and 0.75–10.89 d, respectively, and DT90 was 4.66–162.45 d and 6.44–57.46 d, respectively. The results suggested that soil temperature had significant effects on the degradation of Cry1Ab protein, with a higher degradation rate at higher temperature, but soil water content and pH had no obvious effects on the degradation of Cry1Ab protein.