POLLEN DISPERSAL FROM 2 FIELD TRIALS OF TRANSGENIC COTTON IN THE NAMOI VALLEY, AUSTRALIA

The testing of transgenic crops in the field is a necessary part of th e validation of genetically engineered cultivars, but in the early sta ges of testing, biosafety procedures must be carefully monitored to en sure that the modified plants do not have deleterious effects on the e nvironment. This study was carried out over two seasons to determine t he effectiveness of containment procedures under australian environmen tal conditions by measuring the dispersal of pollen away from a test p lot of transgenic cotton into a surrounding buffer field of non-transg enic cotton plants whose function was to act as a sink for pollen carr ied by nectar feeding and pollen-gathering insects. Dispersal was esti mated by measuring the frequency of the dominant selectable marker tra nsgene, neomycin phosphotransferase (NptII) in the progeny of the buff er plants. The presence of nptii was determined by a sensitive radioac tive enzyme assay. Pollen dispersal was low in both years, but increas ed 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 t o below 0.08% at 4 m from the test plot. Outcrossing was highest withi n the central test plot where progeny from non-transgenic control plan ts, immediately adjacent to transgenic plants, had transgenic progeny at frequencies of up to 1.7% In the second year declined on average fr om 0.4% at 1 m to below 0.03% at 16 m into the buffer zone. These resu lts indicate that 20 m buffer zones would serve to limit dispersal of transgenic pollen from small-scale field tests.