Sterilisation of fritillary bulbs is by 15-20 min in sodium hypochlorite (4–5%), 70% alcohol, 0.1% mercuric chloride, 2% chloramine and sterile distilled water. You can use sodium hypochlorite on its own. Also, see: 'Establishment of in Vitro Culture and Effect of Chilling Treatment of Mother Bulb On Bulblet Formation in Fritillaria thunbergii Miq.'.