Improvement of bulb formation in micropropagated tulips by treatment with NAA and paclobutrazol or ancymidol.

摘要

Bulb formation is an essential stage in tulip micropropagation via cyclic shoot multiplication because only bulbs show high rooting ability and good field performance. The stage of bulb formation in vitro consists of three phases: (1) development of bulb primordia in shoots at the end of the last subculture prior to cooling; (2) induction of bulbing process by cooling of shoots; (3) bulb formation at 23 degrees C. Shoots of tulips 'Prominence', 'Blenda' and 'Blue Parrot' multiplied on the medium with thidiazuron (TDZ), were used for the experiments. The effects of liquid media (with or without growth regulators) added into the shoot cultures prior to cooling were examined in relation to the efficiency of bulb formation. The liquid media were added at the end of the last eight-week-multiplication subculture. 1-naphthylacetic acid (NAA) at 2 mg L-1 and inhibitors of gibberellin biosynthesis, ancymidol or paclobutrazol (1-2 mg L-1) were used. The shoots were grown on double-phase media for six weeks. The control subculture prior to cooling was prolonged to 14 weeks, but the liquid medium was not added. The shoots were then transferred onto the sucrose-rich medium without growth regulators and cooled at 5 degrees C for three months. Subsequently, they were cultured for bulb formation at 23 degrees C for 2-5 months. The application of the liquid medium containing NAA and/or ancymidol or paclobutrazol significantly enhanced the efficiency of bulb formation expressed by the ratio of the properly formed bulb to shoot numbers x 100%. For 'Prominence', it varied from 42.9% noted in control to 60.1-104.2%, for 'Blenda' - from 68.8% in control to 121.7-125.0% and in 'Blue Parrot' bulbing was sporadic in control but on double-phase ranged from 14.5% to 41.6%..