Plant regeneration from induced callus of improved Eucalyptus clones

Plant regeneration through indirect organogenesis was obtained from pieces of in vitro shoots, produced on semi-solid and RITA® systems, of Eucalyptus grandis and E. grandis × E. urophylla clones. Pieces of in vitro shoots (with axillary buds removed) developed callus when cultured on MS salts and vitamins, 30 g l− 1 sucrose, 4 g l− 1 Gelrite, 5 mg l− 1 IAA and 0.25 mg l− 1 BAP. This callus, although produced in small amounts, formed shoots on the same medium. Rooting was achieved when regenerated shoots were cultured in the presence of 1/4 MS, 15 g l− 1 sucrose, 0.1 mg l− 1 biotin, 0.1 mg l− 1 calcium pantothenate, 0.5 mg l− 1 IBA and 4 g l− l Gelrite for 4 weeks. Subsequent acclimatization was achieved (> 90%) when the plantlets were allowed to grow individually in pots containing a mixture of perlite and coir soaked with 1/3 MS salts, and subjected to gradual reductions in humidity. The use of the temporary immersion RITA® system as a source of in vitro shoots for initiation of callus cultures was not successful with one of the tested clones. This result was attributed to the large internodal size of the RITA®-produced shoots of the clone.