ADVENTITIOUS SHOOT REGENERATION FROM IN VITRO-CULTURED LEAVES OF RUBUS GENOTYPES

Regeneration of adventitious shoots from leaves of several in vitro-cultured Rubus genotypes was affected by media components and incubation conditions. Leaves cultured at 20 degrees C with a photosynthetic photon flux (PPF) of 40 mu mol m(-2) s(-1) had a higher regeneration frequency and more shoots per regenerating leaf than ones cultured at 25 degrees C with a PPF of either 40 or 80 mu mol m(-2) s(-1). Thidiazuron (TDZ) was significantly more effective than benzyladenine. Medium containing 1 mu M TDZ had the highest percentage regeneration for leaves of 'Autumn Bliss', 'Canby', 'Summit' and 'Sentry' red raspberries, whereas leaves of MD-ETCE-1 blackberry hybrid responded more to 10 mu M TDZ. Higher regeneration frequencies were obtained with 0.5 mu M indolebutyric acid (IBA) than with 1 mu M, but no significant difference was observed between 0.5 mu M and no IBA in other experiments. More shoots per regenerating leaf formed on Murashige and Skoog (MS) and N6 media than on half-strength MS, Anderson, or Woody Plant media for all genotypes tested. The youngest two expanding leaves near the shoot apex were the most regenerative and yielded the highest number of shoots per regenerating leaf.