Expression and degradation of Cry1Ab protein in Bt hybrid rice and its impacts on ground-dwelling Entomobrya griseoolivata occurrence in postharvest seasons
Abstract:To assess the potential ecological risk of Bt rice plant straw returning to field on nontarget ground-dwelling springtails in postharvest seasons, field expression and postharvest degradation of Cry1Ab protein in Bt hybrid rice Donglong (DL) were determined by using standard ELISA test kits of US EPA. At the same time, the individual numbers of the predominant springtail Entomobrya griseoolivata (Packard) (Collembola: Entomobryidae) were compared between DL and their non-parental control rice lines Xianyou 46 (XY) or Xinongyou 1 (XN) in postharvest paddy fields. Results showed that the Cry1Ab concentrations in the leaf blades, stems and roots of DL were 2.49-16.13μg/g fresh weight in different developmental stages. The Cry1Ab could persist in DL plant litters for a long term after rice straw returning-to-field in postharvest seasons, and the Cry1Ab concentrations of the ground litters of stem and leaf, the rice plant stubbles and the root litters were 0.072, 0.074 and 0.033μg/g dry weight at 132 day, respectively. The population densities of E.griseoolivata between DL and XY or XN fields were not significantly different, and the population dynamics of E.griseoolivata in DL field is similar to the two controls in most cases.