Production of embryogenic tissues and regeneration of transgenic plants incassava (Manihot esculenta Crantz)

Disorganised embryogenic tissues have been utilised as target tissues for t ransgene insertion and transgenic plant regeneration in cassava (Manihot es culenta). The production of friable embryogenic callus in fourteen geograph ically diverse cassava cultivars, from which eleven were established as emb ryogenic suspension cultures, is reported. Embryogenic tissues were similar in nature in all cultivars tested although there was variation in the time required to generate friable callus and the growth rates of suspension cul tures. Regeneration of plants has been achieved from eight cultivars but va ried significantly in efficiency, with cv. TMS 60444 and Line 2 from Zimbab we being the most responsive. Tissues from the remaining eight cultivars be came arrested at globular and torpedo stages of regeneration indicating tha t they most likely process an inherent ability to produce plants but requir e further research to allow this to be realised. Significant numbers of tra nsgenic plants containing transgenes for putative resistance to important v iral diseases of cassava in addition to visual marker genes have been regen erated. Transgenic plants from three the cultivars TMS 60444, Bonoua Rouge and M.Col 1505 were recovered after particle bombardment of embryogenic sus pension cultures. Correlation's have been made between abnormal leaf morpho logy and plant vigour with the use of embryogenic suspension cultures for t ransgene insertion. As an result friable embryogenic callus is now being su ccessfully utilsed as the target tissue for genetic transformation and plan t regeneration at ILTAB.