THIDIAZURON-INDUCED PLANT-REGENERATION FROM PROTOPLASTS OF VICIA-FABACV MYTHOS

Protoplasts of 10 cultivars of V. faba were isolated from etiolated sh oot-tips and tested for their regeneration capacity. After purificatio n, protoplasts were embedded in sodium alginate and cultivated in the medium of Kao and Michayluk (1975) containing 0.5 mg . l(-1) of each 2 ,4-dichlorophenoxyacetic acid, naphthylacetic acid and 6-benzylaminopu rine. Depending on cultivar, division frequencies of up to 40% were ob tained. Six weeks after embedding, protoplast-derived calluses were tr ansferred to Gelrite-solidified media with different combinations of g rowth regulators. A two step protocol (auxin high/low) was tested for its ability to induce somatic embryogenesis. The formation of globular structures was observed, but no embryo formation could be achieved. I n contrast, cultivation of protocalluses on medium supplemented with t hidiazuron resulted in shoot development in cultivar Mythos. To genera te mature plants, the shoots were grafted onto young seedlings. In ord er to optimize the in vitro-conditions, different concentrations of th idiazuron alone or in combination with naphthylacetic acid were tested , showing that an increase of thidiazuron and the addition of naphthyl acetic acid positively affects both the viability of protocalluses and the regeneration frequency.