ESTABLISHMENT OF A SUCCESSIVE CULTURE OF AN OBLIGATORY PARASITIC FLOWERING PLANT, CUSCUTA-JAPONICA, INVITRO

A culture system of an obligatory parasitic flowering plant, Cuscuta japonica, was established for studying parasitic behavior and floral evocation. The culture system consists of culturing excised stems of aseptic Cuscuta seedlings on a modified Murashige and Skoog medium containing 1 mg . l-1 of kinetin and 10% coconut water (K-medium). When the excised stem was incubated horizontally on the K-medium under continuous light conditions, novel protuberances developed from cut ends of the stem, and subsequently lateral buds elongated into lateral shoots. The lateral shoots with the novel protuberances grew rapidly and resembled the parasitizing plants in the field. These lateral shoots were propagated by successively culturing the stems excised from newly elongated lateral shoots, and the subcultured lateral shoots occasionally projected a few haustorium-like organs. The lateral shoots cultured in vitro could parasitize in vivo on the stem of host plants grown in a flower pot, and after that the parasitizing plants bloomed and developed seeds. Moreover, when the subcultured lateral shoots were cultured under short day conditions, floral buds developed on the elongated lateral shoot. The anthesis and seed development progressed in this in vitro culture.