Stable maintenance and expression of a foreign gene in transgenic pear shoots retrieved from in vitro conservation

Shoot-tips of transgenic pear were successfully conserved in vitro by slow-growth and cryopreservation methods. After 1 year of storage in slow growth conditions, all shoot-tips survived showing shoot re-growth. Similarly, shoot-tips showed high survival and regeneration rates after cryopreservation. The genetic stability of the transgenic GUS construct in shoots recovered from slow-growth and cryopreservation was assessed. The results from polymerase chain reaction and Southern blotting showed the stable maintenance of the GUS gene in genome, and the Single-Strand Conformation Polymorphism assay did not detect single base variation. X-Gluc staining suggested a normal expression of the GUS gene in shoots retrieved from these storage methods.