T5 PM Emerging Pollutants
Tuesday, 15 November 2005: 1:50 PM - 5:30 PM in 321-323

(GAG-1115-728736) Occurrence and persistence of Bacillus thuringiensis Cry1Ab genes in the aquatic environment near a transgenic corn field.

Gagné, F.¹, Douville, M.¹, André, C.¹, Blaise, C.¹, ¹ Environment Canada, Montréal, Québec, Canada

ABSTRACT- Genetically modified corn crops are being used to control pest infestations from insects of the Lepidoptera family. Cry1Ab endotoxin derived from Bacillus thuringiensis ssp. Kurstaki (Bt) have successfully inserted in corn crops. The aims of this study were to examine for the occurrence and persistence of Cry1Ab genes in aquatic environments in the vicinity of Bt-corn fields. First, an optimal DNA preparation and extraction method was developed to allow gene analysis by real time polymerase chain reaction from various environmental samples. Second, in vitro spiking experiments with Bt or Bt corn DNA to surface waters and sediments were examined to evaluate their relative persistence in the environment. Third, Soil, sediment and water samples were collected before seeding, 1-2 weeks after pollen release and after harvesting and composting for the presence of Cry1Ab gene and protein. The results showed that DNA was readily extracted and relatively pure i.e., high absorbance at 260 nm/absorbance at 230 nm ratio and absence of PCR inhibiting substances from soil, sediments and surface waters. Persistence experiments revealed that Cry1Ab in surface waters and sediments persisted for more than 21 and 40 days respectively. The removal of bacteria by filtration in surface waters did not increase significantly the t1/2 of the transgene but their levels were 5 fold more abundant than with unfiltered water at the end of exposure time. In sediments, Cry1Ab from either Bt and Bt-corn were still detected after 40 days in clay and sand rich sediments. Field surveys revealed that Cry1Ab transgene (corn) and from naturally-occurring Bt products were more prevalent in the sediment compartment than with surface waters. The Cry1Ab transgene was detected down to the Richelieu and St-.Lawrence rivers suggesting multiple sources of these genes and/or transport on large scale. Sediment associated Cry1Ab from Bt-corn tended to decreased downstream to the cultivation field and was significantly correlated with Cry1Ab in surface waters (R=0.82; p<0.01). The data indicate that released DNA from Bt-corn and Bt are fairly persistent in the aquatic environments and are detected in aquatic environments draining agricultural areas.

Key words: Cry1Ab gene, Transgenic corn, Aquatic ecosystems