Factors affecting micropropagation of pathogen-free stocks in Fritillaria thunbergii

Scale segments of Fritillaria thunbergii were cultured in Murashige-Skoog ( MS) medium supplemented with 3-5 mg/l kinetin to produce bulblets. Bulblets formation were promoted by the moisture storage of the mother bulbs at 10 degrees C for 4-6 weeks before the excision of explants. The inflorescence stem was the best explant source for the bulblet formation compared with ot hers. The best treatment for bulblet growth was the addition of 10-100 mg/l succinic acid 2,2-dimethylhydrazide (B-9) or chloromequet to the MS medium combined with high concentration of sucrose. The leaf emergence rate after transplanting the bulblets into the soil was remarkably promoted by long-t erm cold storage. It needed at least 6 weeks to break the dormancy of bulbl ets grown at 6% sucrose condition. By the incorporation of Vidaravine over 50 mg/l, symptoms of virus infection were drastically decreased even though survival rate declined. Plants showing such symptoms were severely infecte d by tobacomovirus.