Restoration of regeneration potential of long-term cultures of red fescue (Festuca rubra L.) by elevated sucrose levels.

A tissue culture protocol for restoring embryogenic ability and increasing green plant regeneration from long-term callus (5-year old) and suspension cultures of "Dawson" red fescue (Festuca rubra var trichyoplylla Gaud) was developed. Pretreatment with elevated levels of sucrose over the standard level (60 mM) enhanced regeneration capacity and decreased the number of albino plants. The highest degree of embryogenesis and green shoot number occurred when calli were pre-treated on MS basal medium supplemented with 120 mM sucrose. Mannitol caused callus discoloration and death if added to pre-treatment media at 60, 90, 120, 150 or 180 mM. Cell suspension growth was greatest when 135 mM sucrose was added to the pre-treatment growth media. High concentrations of sucrose (135 and 180 mM) were necessary for plant regeneration from suspension aggregates pretreated with 135 or 180 mM sucrose and then plated on a growth regulator-free regeneration medium composed of half-strength MS salts and B5 vitamins.