[Accumulation of Cry proteins in soil released from Bt rice after planting for multiple years].

protein residue and accumulation in soil are two important components of the environmental safety assessment for the plantation of transgenic crops. Several rice lines with good commercial prospects have been developed in China, but it is unclear whether proteins will accumulate in soils after multiple years of rice cultivation. We planted the transgenic rice lines Minghui 63 (Huahui No. 1) and Minghui 63 for 9 years in the same field. The proteins in the rhizosphere soil were estimated with enzyme linked immunosorbent assay (ELISA) at tillering stage and on the 60th day after harvest in each year. The protein residues during the seedling, flowering and ripening stages were estimated in the first year (2012) and the last year (2020) of the experiment. In 2012, the concentration of in the rhizosphere soil of Huahui No. 1 was 1.25, 1.77, 1.97, 1.71 and 0.30 ng·g at the seedling, tillering, flowering, ripening stages and on the 60th day after harvest, respectively. In 2020, the corresponding values were 1.30, 1.69, 2.03, 1.77, and 0.43 ng·g. In 2012, the concentration of in rhizosphere soil of line Minghui 63 was 0.91, 1.52, 1.53, 1.37, and 0.12 ng·g at the seedling, tillering, flowering, ripening stages and on the 60th day after harvest, respectively. The corresponding values in 2020 were 0.95, 1.43, 1.61, 1.40, and 0.15 ng·g. Results of multi-way ANOVA showed that the effect of year was not significant, but the effects of rice variety and growth stage were significant. Our results indicated that proteins could be detected in rhizosphere soil during the growth stages of rice, but would be degraded by 60 d after harvest, and that the concentrations of proteins in the soil would not accumulate across multiple planting years.