The agar is one of the most expensive componnts in a tissue culture medium when vitro propagation is concerned. This work was carried out in the tissue culture laboratory at EMBRAPA/CPACT, Pelotas RS. The objective of this work was to test the agar action and its partia1 substitution for cassava starch in the composition of the solidifying agent in the MS basal medium associated winth 0; 2.5; 5.0; 7.5 and 10.0µM indolyl butyric acid (IBA). The solidifying agents were as fallows: agar (6g.L-1) agar (3g.L-1) + cassava starch (50g.L-1). The MS basal medium was reduced to half strength and added to myo-inositol (100mg.L-1); sucrose (30g.L-1) and the pH adjusted to 5.9 before autoclaving. The explants were kept for 30 days in the growth room under 25±2°C, 16-hour photoperiod and about 2000 lux light intensity. The use of agar + starch promoted a higher number of roots, and a maximization was observed in the presence of 5µM IBA. It also antecipated the new roots in about 10 days. The consistency of the agar/starch was quite the same as agar e it appeared less transparent.
micropropagation; gelling agent; auxin; Malus
