Abstract: 【Objective】The environmental fate of Bt insecticidal protein released by Bt rice plants in paddy soils is a key issue in its ecological risk assessment. 【Method】 In the present study, impacts of soil water content, pH and temperature on the degradation of Cry1Ab protein expressed in leaves of Bt rice KMD2 were studied in the laboratory. Three types of paddy soils were used, i.e., blue clayey paddy soil, pale paddy soil on quaternary red soil, and marine-fluvigenic yellow loamy paddy soil. Ground powders of KMD2 leaf-blades were mixed with each type of soil, and degradation dynamics of Cry1Ab were determined using standard ELISA QuantiplateTM kit (EnviroLogix, USA).【Result】The degradation rate of Cry1Ab was high at the early experimental stage, but it slowed down steadily at middle and later stages, which could be described by exponential equations with the half-life period of degradation determined as 1.8-4.0 d. 【Conclusion】The soil water content, pH and temperature could affect the degradation of Cry1Ab, but soil pH and temperature were relatively greater. In general, Cry1Ab degradations were slower under lower soil pH and temperature conditions, especially for marine-fluvigenic yellow loamy paddy soil.

Key words: Transgenic Bt rice, Cry1Ab insecticidal protein, Paddy soil, Degradation, Environmental factor