Shoot regeneration from cultured root explants of spinach (Spinacia oleracea L.): a system for Agrobacterium transformation.

A reliable plant regeneration system is described for the production of adventitious shoots from root explants of spinach. Explants from roots of axenic shoots and roots induced on cultured hypocotyl explants were used for adventitious shoot induction. Explants from apical, middle and basal root regions were incubated on Nitsch and Nitsch medium supplemented with α-naphthaleneacetic acid, gibberellic acid and kinetin. Optimum shoot regeneration was from explants of apical and middle root regions on medium with 20 µM α-naphthaleneacetic acid and 5.0 µM gibberellic acid. Shoots originated directly from root tissues without an intervening callus phase. Adventitious shoots were rooted and were grown to maturity in the glasshouse. This plant regeneration procedure has been exploited in preliminary studies of Agrobacterium-mediated transformation.