Antiauxin enhanced microshoot initiation and plant regeneration from epicotyl-originated thin-layer explants of sugarbeet (Beta vulgaris L.)

An in vitro method was developed for microshoot initiation from thin-layer explants prepared from the elongated epicotyls of sugarbeet (Beta vulgaris L.). Intact epicotyls of 14-day-old seedlings were excised from the hypocotyls above the cotyledons and allowed to elongate on De Greef and Jacobs (1979) medium supplemented with 0.2 mg/l 6-benzyladenine, 0.2 mg/l gibberellic acid and 0.1 mg/l indole-3-acetic acid in darkness. 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 thick tangential sections were prepared longitudinally from the exterior parts of the halved epicotyls. These thin-layer explants were incubated 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 development (6.3±0.2 microshoots/thin-layer explant). The final efficiency of our tissue culture system was significantly increased by the NaCl (100 mg/l) initiated in vitro rooting of microshoot originated plantlets.Abbreviations AC activated charcoal - asdp apical segment derived plantlet - asTLE apical segment derived thin-layer explant - BA-6 benzyladenine - bsdp basal segment derived plantlet - bsTLE basal segment derived thin-layer explant - EEM1-4 epicotyl elongation media - GA₃ gibberellic acid - GM germinating medium - IAA indole-3-acetic acid - IBA indole-3-butyric acid - KN kinetin - MES morpholino-ethanesulfonic acid - MSI1-6 microshoot initiating media - NAA -naphthalene acetic acid - PG_oB De Greef and Jacobs (1979) medium - RM1-3 rooting media - SDM shoot developing medium - SE standard error - TIBA 2,3,5 triiodobenzoic acid - TLE thin-layer explant - ZEA zeatin