Abstract: Two transgenic rice lines, KMD2 and Huachi B 6, both contain a synthetic cry1Ab gene from Bacillus thuringiensis (Bt) under the control of maize ubiquitin promoter, were used in the laboratory to examine the degradation of Cry1Ab toxin proteins from Bt transgenic rice in paddy soils. Ground leaves of KMD2 and whole leaf-blades of Huachi B6 were separately buried in each of three types of soil, i. e. pale paddy soil on quaternary red soil, blue clayey paddy soil and marine-fluvigenic yellow loamy paddy soil, and thereafter residues of Cry1Ab in the KMD2-leaf-mixed soils and Cry1Ab in the buried Huachi B 6 leaves were examined at an interval of 6-10 days. Cry1Ab in ground leaves of KMD2 degraded rapidly in all the soils during 36 days after treatment (DAT), particularly during the first six DAT, with the highest degradation rate in blue clayey paddy soil and the lowest in marine-fluvigenic yellow loamy paddy soil. During 6-36 DAT, the highest Cry1Ab residue was observed in marine-fluvig enic yellow loamy paddy soil, mediate in pale paddy soil on quaternary red soil, and the lowest in blue clayey paddy soil, with significant difference tested among soils at each of observation times; however, such difference decreased gradually as time proceeded thereafter, and became fairly little at 78 DAT. As the soil was flooded, the degradation of Cry1Ab in buried leaves of Huachi B 6 was significantly accelerated, and exhibited a similar pattern among all of the flooded soils. Such impacts of flooding occurred only in the first 12 DAT, and during most of the subsequent periods no significant difference could be observed in Cry1Ab residue between the flooded and unflooded treatments. Degradation kinetics of Cry1Ab toxin proteins were fitted to exponent equation in each treatment, and half life of the toxin protein was determined. Finally, impacts of micro-organism and organic matter content in soils on the degradation of Cry1Ab were discussed.

Key words: transgenic rice, toxin protein, paddy soil, degradation

摘要： 室内研究了转Bt基因水稻克螟稻2号和华池B6叶片中的Cry1Ab杀虫蛋白在稻田水稻土中的降解动态。分别将克螟稻2号的粉碎叶片和华池B6的整张叶片埋入3种土壤（即老黄筋泥田、青紫泥田和黄松田）中，此后每隔6~10 d测定土壤或叶片中的Cry1Ab含量。克螟稻2号粉碎叶片中的Cry1Ab均以处理后的前36 d, 尤其是前6 d的降解较快，其中在青紫泥田中最快，黄松田中最慢。在处理后6~36 d内，不同土壤中的Cry1Ab残留量有显著差异，黄松田中的明显最高，老黄筋泥田中的次之，青紫泥田中的为最低；此后土壤间的残留量差异逐渐缩小，至处理后78 d差异已不明显。土壤淹水可显著加快华池B6叶片中Cry1Ab的降解，且淹水后其降解动态在不同土壤之间十分相似；淹水对Cry1Ab降解的促进作用仅发生在前12 d之内，此后多数时间内残留量在淹水与非淹水处理间无显著差异。建立了各处理中Cry1Ab降解的动力学指数方程，相应地得出了其降解的半衰期。还讨论了土壤有机质和微生物等因子对土壤中Cry1Ab降解的影响。

关键词: 转基因水稻, 杀虫蛋白, 水稻土