Up to 4 generations of plants from selfing and outcrossing have been examined in lines containing stable integrated genes. In these lines, segregation ratios conformed to expected Mendelian inheritance and no loss of activity of the introduced characters was detected. It was concluded that the selection of stable lines for use in plant breeding would be possible.
Beta glucuronidase was found to be a useful marker for use in field grown plants, showing little increase in background levels during a trial. Variation in activity within a plant, between replicate plants and in relation to environmental factors has been quantified.
The plant lines grown in the field trials were 2 to 4 generations after transformation. These had been previously selected in containment to have normally morphology. This was maintained in the field of no abnormality associated with the modifications was found. A small but consistent difference was present between the lines in plant height; the nonmodified lines were shorter than the modified lines at an early stage but not after flowering. The plant height was associated with differences between the lines in the time of flowering.
A cordon of nonmodified plants surrounding the experimental plants was included in several of the trials. Seed samples from these plants have been screened for kanamycin resistance, to examine the extent of cross pollination with the modified plants. Kanamycin resistance was found to be a useful selectable marker for this procedure in tobacco, enabling largenumbers of progeny (100000 per trial) to be screened rapidly. The frequency of resistance progeny and the distribution of their parental plants in the field have been analysed in relation to the environmental factors that may have influenced pollen dispersal.