Biosafety Assessment of Transgenic Crops in the Soil Environment

Abstract

Transgenic papaya expressing the PRSV gene is the first transgenic crop developed in Taiwan. This paper describes the horizontal gene transformation (HGT) of the kanamycin-resistant gene, nptII , from transgenic papaya, and the persistence of transgenes in the soil. Two strains of Acinetobacter spp., BD413and BD413 (pFG4AnPtID, were used as recipient cells. Our experiments suggested that HGT of genomic DNA transfer might be less likely to occur in soil. The persistence of transgenes in the soil was evaluated by seven soil DNA extraction methods, and the method of using CTAB/SDS/gel (cetyltrimethylammonium bromide/sodium dodecyl sulfate/gel purification) was the best with 45.8% DNA recovery. The detection limit of transgenic DNA in soil for real-time polymerase chain reaction (PCR) was 0.3 ng/g soil (dry). Specific transgenic sequences inserted in the genome of transgenic papaya were detected in soil for 5 months, and the persistence of the 398-bp fragment (pBll21/N05-t) in soil samples was less than 0.16 Pg/g soil, whereas the residues of the 769-(355*P/PRSV-CP) and 200-bp fragments (NOS-P/nptII) were less than2.0x 10-4 " g/g soil. concentrations of the nptII gene in soil were very low; therefore, the risk for horizontal gene transfer of the nptll gene in soil is very low.