EFFECT OF GELLING AGENTS AND ANTIBIOTICS ON ADVENTITIOUS BUD REGENERATION FROM IN-VITRO LEAVES OF PEAR

The effect of the type of gelling agent and of several antibiotics on the adventitious bud regeneration from in vitro leaves was tested on e ight pear genotypes. The use of gellan gum (Phytagel(TM)) in the mediu m instead of agar had a very strong positive effect on the rate of adv entitious bud regeneration for all pear genotypes tested in this study . This gelling agent induced faster cell divisions than agar, thus mor e callus was produced on wound sites and subsequently more buds regene rated. Incubation on gellan gum medium during the first 20 d of bud in duction was sufficient to induce a stimulatory effect on regeneration and limited the production of hyperhydric buds. In the prospect of Agr obacterium transformation, the effect of several antibiotics was teste d. Cefotaxime (200 mg/l) plus ticarcillin/clavulanic acid (100 mg/l) c ould be used in the culture medium without affecting the frequency of bud regeneration. The inhibition of bud regeneration was obtained with different kanamycin concentrations according to the gelling agent in the medium. On gellan gum medium, a concentration of 100 mg/l of kanam ycin was suitable. These conditions can be recommended for experiments on Agrobacterium-mediated transformation of pear, where bacterial ino culation and presence of antibiotics generally reduce and delay bud re generation.