Pollen dispersal from two field trials of transgenic cotton in the Namoi Valley, Australia

Abstract

The testing of transgenic crops in the field is a necessary part of the validation of genetically engineered cultivars, but in the early stages of testing, biosafety procedures must be carefully monitored to ensure that the modified plants do not have deleterious effects on the environment. This study was carried out over two seasons to determine the effectiveness of containment procedures under australian environmental conditions by measuring the dispersal of pollen amay from a test plot of transgenic cotton into a surrounding buffer field of non-transgenic cotton plants whose function was to act as a sink for pollen carried by nectar feeding and pollen-gathering insects. Dispersal was estimated by measuring the frequency of the dominant selectable marker transgene, neomycin phosphotransferase (NptII) in the progeny of the buffer plants. The presence of nptii was determined by a sensitive radioactive enzyme assay. Pollen dispersal was low in both years, but increased with an increase in the size of the source plot in the second year. In the first year outcrossing averaged from 0.15% of progeny at 1 m to below 0.08% at 4 m from the test plot. Outcrossing was highest within the central test plot where progeny from non-transgenic control plants, immediately adjacent to transgenic plants, had transgenic progeny at frequencies of up to 1.7%. In the second year, with a bigger source of transgenic plants, outcrossing declined on average from 0.4% at 1 m to below 0.03% at 16 m into the buffer zone. These results indicate that 20 m buffer zones would serve to limit dispersal of transgenic pollen from small-scale field tests.