ADVENTITIOUS SHOOT PRODUCTION FROM STRIPS OF STEM IN THE DUTCH ELM HYBRID COMMELIN - PLANTLET REGENERATION AND NEOMYCIN SENSITIVITY

The regenerative ability of small strips of stem of the Dutch elm hybr id 'Commelin' was tested as well as its sensitivity to neomycins. Camb ium explants (1 mm thick), were excised from woody stems collected in the field. Up to 20 buds/explant were induced within 2-3 weeks giving 2-5 rootable shoots/explant after 5-6 weeks. Shoot excision every week from week three improved the yield up to 7 shoots per explant. Fourte en and 2.9 mu M GA(3) promoted shoot growth. Cytokinins (1 mu M zeatin or 5 mu M BA or 0.05 mu M TDZ) completely inhibited shoot production and promoted callus formation. Kanamycin and paromomycin at between 24 0 and 360 mu M inhibited shoot formation as did geneticin at 80 mu M. The shoot-forming ability of the explants was high from leaf fall in t he autumn to the spring flush, but could be maintained up to September by using cold storage (5-7 degrees C). Ninety-six percent of the shoo ts rooted with 0.5 mu M IBA and were successfully acclimatized despite having a large basal callus.