High frequency shoot induction and plant regeneration from cotyledonary hypocotyl explants of cucumber (Cucumis sativus L.) seedlings

A method of high frequency shoot induction was established using excised hypocotyl segments bearing cotyledons (referred to as cotyledonary hypocoryl explants) of cucumber (Cucumis sativus L.) seedlings. Adventitious shoots were obtained from the upper excised hypocotyls of cucumber seedlings incubated on Murashige and Skoog (MS) medium containing 2.0 mg/L zeatin. The effects of cotyledon size and hypocotyl length of seedlings on shoot organogenesis were also examined. A higher frequency (80–90%) of adventitious shoots was obtained from explants of 3- and 5-day-old seedlings with either 1 cotyledon or 2 half-cotyledons, and a short hypocotyl length (2 mm). However, explants with long hypocotyls and 2 cotyledons produced fewer shoots. Adventitious shoots from cotyledonary hypocotyl explants were removed and rooted in MS medium containing 1.0 mg/L IAA. The rooted plantlets developed into normal plants after acclimatization to ambient humidity levels.