VEGETATIVE PROPAGATION OF ADULT EUCALYPTUS-GRANDIS X UROPHYLLA AND COMPARISON OF GROWTH BETWEEN MICROPROPAGATED PLANTLETS AND ROOTED CUTTINGS

Methods for the production of micropropagated plantlets and rooted cut tings were developed and used to vegetatively multiply adult Eucalyptu s grandis X urophylla. Rooting success was less than 5% when cuttings excised from twigs of 3-year-old trees were used. The rooted cuttings were grown in the greenhouse as explant- or cutting-donors and maintai ned at a height of 30 to 100 cm by trimming back periodically. Good ro oting success (95%) of cuttings was obtained for epicormic shoots prod uced from donor plants after trimming 5 times. Explants of both apical and axillary buds taken from the donor plants produced multiple shoot s when cultured in vitro. In vitro multiple shoot production was optim al on MS medium containing 0.1 mg/l BA and 0.01 mg/l NAA, averaging 13 .7 shoots per explant in a 40-day culture period. Shoot elongation was accelerated on a modified MS medium containing half strength potassiu m nitrate and sucrose. Elongated shoots excised at approximately 1.5 c m in length were successfully rooted on media with NAA or IBA concentr ations ranging from 0.1 to 10 mg/l. Root formation was optimal on medi um consisting of full strength MS basal macro elements and vitamins, h alf strength micro elements, 1% sucrose and supplemented with 0.3 mg/l IBA. In the field test, no significant differences were found in tree height and DBH between micropropagated plantlets and rooted cuttings at I and 3 years old, with the exception at 2 years old. A considerabl e difference arose between the 2 types of vegetative propagules in phy siological response to flowering, caused by dissimilar degrees of reju venation.