Abstract
Mesophyll protoplasts of six lines of Silybum marianum were enzymatically isolated from young leaves, embedded in sodium alginate, and cultivated
in KM-medium. Division frequencies observed after ten days were strongly influenced
by the protoplast density. When 5 × 104/ml protoplasts were plated, division frequencies of about 35% were obtained, with
a protoplast population density of 1 × 105/ml division frequencies 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 one (M 24) and up to 7% in
a second line (M 2), respectively. However, when the protocalluses from line M 2 were
treated with thidiazuron (TDZ) in a first culture step, and with BAP in a second step,
the shoot formation frequency rose to 22%. Shoots were rooted on hormone free MS agar
medium and transferred into soil where plants grew to maturity. Similar results were
obtained when protoplasts of the line M 2, isolated from a suspension culture, were
cultivated.
Key words
Silybum marianum (L.) Gaertn. - Asteraceae - protoplasts - sodium alginate - thidiazuron - plant regeneration
