Efficient shoot organogenesis of begonia (Begonia rex Putz.) induced by thidiazuron

The effects o f thidiazuron (TDZ) on adventitious shoot bud formation from leaf and peti­ ole explants excised from in-vitro-grown plantlets o f a begonia were tested by a two-step procedure: a short exposure (5 to 120 min) to 40 pM TDZ in liquid MS medium followed by culture on agar-solidified MS medium without growth regulators. Exposure of explains for five min to TDZ induced bud formation, but the number o f buds was in­ creased with prolonged exposure. Sixty min exposure to TDZ resulted in the highest mean number o f regenerated shoots (24/leaf disc: 44/petiole segment after five weeks o f cul­ ture). Shoots generated after two weeks in culture without, or with a small amount of, cal­ lus. During the third and fourth week in culture shoots developed small roots, and from the mother explant separated shoots elongated and further developed. The sucrose concentra­ tion in the basal expression medium influenced the efficiency of shoot organogenesis. The frequency of shoot formation tended to increase when the medium was supplemented with 2% sucrose instead with 3%.