ANTIAUXIN ENHANCED MICROSHOOT INITIATION AND PLANT-REGENERATION FROM EPICOTYL-ORIGINATED THIN-LAYER EXPLANTS OF SUGAR-BEET (BETA-VULGARIS L)

An in vitro method was developed for microshoot initiation from thin-l ayer explants prepared from the elongated epicotyls of sugarbeet (Beta vulgaris L.). Intact epicotyls of 14-day-old seedlings were excised f rom the hypocotyls above the cotyledons and allowed to elongate on De Greef and Jacobs (1979) medium supplemented with 0.2 mg/l 6-benzyladen ine, 0.2 mg/l gibberellic acid and 0.1 mg/l indole-3-acetic acid in da rkness. After a 21-day-incubation, the elongated epicotyls were halved to obtain apical and basal segments prior to removing the leaves and lateral buds. Subsequently, 5-8 mm long, 2-3 mm wide and 0.8-1.0 mm th ick tangential sections were prepared longitudinally from the exterior parts of the halved epicotyls. These thin-layer explants were incubat ed on microshoot initiating media containing various growth regulators . The combination of 1.0 mg/l 6-benzyladenine and the antiauxin 2,3,5- triiodobenzoic acid (1.0 mg/l) resulted in maximum microshoot developm ent (6.3+/-0.2 microshoots/thin-layer explant). The final efficiency o f our tissue culture system was significantly increased by the NaCl (1 00 mg/l) initiated in vitro rooting of microshoot originated plantlets .