REGENERATION OF CASSAVA PLANTS VIA SHOOT ORGANOGENESIS

A novel regeneration system based on direct shoot organogenesis is des cribed for cassava. Plants could be regenerated at high frequency by i nducing shoot primordia on explants derived from cotyledons of cassava somatic embryos. After a passage on elongation medium, the regenerate d shoots were easily rooted in hormone-free medium and could be succes sfully transplanted to soil. Using the shoot-organogenesis-based regen eration method, up to eight transplantable plantlets per explant could be regenerated. The system was optimised first for one cassava cultiv ar, and then its transferability to three other cultivars was demonstr ated. This method widens the scope of in vitro regeneration modes of c assava, and is also compatible with Agrobacterium-mediated transformat ion. To develop an efficient system for production of somatic embryos for regeneration experiments. conditions for inducing primary and cycl ing somatic embryos were also studied, and highly efficient plant rege neration via germination of somatic embryos was achieved using maltose instead of sucrose in the culture medium, and combining paclobutrazol with 2,4-dichlorophenoxyacetic acid in the embryo induction medium.