Molecular validation of the pollen-mediated transgene flow (PMTF) assessment method by testing seedlings from a subset of open-pollinated recipient trees during two years (2005 and 2006).

1Number of transgenic seedlings was determined by GUS expression in leaves and confirmed by PCR analysis of the uidA transgene. False GUS negative seedlings were not found in any case.
2PMTF frequency was calculated as the percentage of transgenic seedlings from the total number of seedlings analyzed per year.
3For each year, χ2 tests were performed to compare the PMTF frequencies obtained by this method with the PMTF frequencies obtained by testing GUS expression in seeds (Table 2). The critical value for 1 df at a 95% confidence level is 3.84.