Achievements and problems in the implementation of microcutting technology for clonaI rubber rootstock propagation

Microcutting is one of in vitro plant propagation methods and has been developed for rubber (Hevea brasiliensis) by using axillary buds from young seedlings as explant sources. There are some constraints to implement microcutting technology in mass propagation of Hevea such as high level of contamination, low proliferation rate, poor rooting, and difficulty in acclimatization process. Achievements and problems in the implementation this technique in Indonesia will be reported in this paper. Around 19.000 explants from 89 genotypes have been introduced in primary culture for almost 3 years (2006-2008), 40% of them loss during this stage due to contamination and no response of the explants. All healthy and good response explants had been transferred to multiplication phase. The multiplication rate was 1.3 to 1.6 per month for the best genotypes. In 2007 and 2008, around 6.000 new shoots had been introduced to conditioning phase, 80% of them have continued to rooting phase. These two stages produced about 4.000 plantlets which were then acclimatized to ex vitro conditions on different media and micro-environments. The suitable medium for vitroplants acclimatization was a mix of cocopeat, soil, sand and dung manure. Better growth and survival rate were achieved when the vitroplants were cultured inside a closed plastic tunnel placed under tree canopies. The survival rate of vitroplants, 1.5 month after weaning, has increased to 60% but still fluctuated and only 15% in average after 6 months. The survived plants with good root systems were then transferred to a shading nursery. Vitroplants and GT 1 seedlings were planted in the field for 7 months before budded with scions of PB 260 clone. All rootstocks from vitroplants and GT 1 seedlings were successfully budded with scions of PB 260. At present, budded and unbudded vitroplants are being planted in the field. (Résumé d'auteur