Abstract
In vitro cultural conditions were investigated for promoting differentiation and growth of bulblets from segments of various parts of plantlets regenerated through shoot-tip culture of lilies (Lilium spp.). The growth and flowering of the in vitro propagated bulblets were observed in soil culture, and diagnosis of virus was also performed under electron microscope and by sap inoculation to L. formosanum seedlings.
1. Bulblet differentiation from various tissue segments and the growth of bulblets were enhanced with addition of auxin, especially 0.1mg/l NAA, to the medium. Addition of cytokinin to the medium multiplied the differentiation of bulblet primordia (adventitious buds) remarkably, but retarded their development to bulblets.
2. Cutting bulb scales into segments increased total number of regenerated bulblets per scale.
3. High sucrose concentration of the medium (60-120g/l) and high incubation temperature (27-28°C) inhibited leaf elongation from bulblets and promoted enlargement of the base of scaly leaves.
4. Although both leaf and stem-node segments regenerated bulblets, bulb scales were most suitable material for in vitro propagation of lilies because of their high regeneration rate of bulblets and simplicity of their culture process.
5. In L. longiflorum, in vitro propagated bulblets flowered without cold treatment within one year after transplanting to soil, and bulbs with marketable size for cut-flower production were harvested in the first cultivation in soil. On the other hand, cold treatment to the bulblets of L. speciosum accelerated bolting in soil culture and reduced days to flowering. In the case of L.×formolongo and L. concolor, bulblets propagated by in vitro culture could flower earlier than by conventional cultivation methods in field conditions. Lilies like these two species are considered to be promising materials for practical production of bulblets through in vitro culture.
6. Diagnosis of virus in bulblets derived from shoot-tip culture of L. longiflorum indicated that these bulblets were freed from virus.
These results suggested that a large number of virus-free lily bulbs can be propagated in a short time by subculturing bulb scales of in vitro bulblets derived from shoot-tip culture, and that the cultivation time necessary to flowering-bulb production can be reduced remarkably by use of those bulbs.
