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.