PLANT-REGENERATION FROM MESOPHYLL AND SUSPENSION PROTOPLASTS OF SILYBUM-MARIANUM

Mesophyll protoplasts of six lines of Silybum marianum were enzymatica lly isolated from young leaves, embedded in sodium alginate, and culti vated in KM-medium. Division frequencies observed after ten days were strongly influenced by the protoplast density. When 5 x 10(4)/ml proto plasts were plated, division frequencies of about 35 % were obtained, with a protoplast population density of 1 x 10(5)/ml division frequenc ies of about 75 % resulted. Plant regeneration experiments undertaken with the protocalluses on medium containing BAP led to shoot formation in only two lines with regeneration frequencies of less than 1% in on e (M24) and up to 7% in a second line (M2), respectively. However, whe n the protocalluses from line M2 were treated with thidiazuron (TDZ) i n a first culture step, and with RAP in a second step, the shoot forma tion frequency rose to 22 %. Shoots were rooted on hormone free MS aga r medium and transferred into soil where plants grew to maturity. Simi lar results were obtained when protoplasts of the line M2, isolated fr om a suspension culture, were cultivated.