High frequency, direct shoot regeneration from greenhouse-derived leaf disks of six strawberry cultivars.

Leaf disks derived from either two-month-old GreenHouse-grown (GHD) strawberry plants or in vitro plantlets were cultured on MS media amended with 2 mg L(-1) Thidiazuron (TDZ), incubated for four weeks in the dark then for another four weeks under 16/8 h light regime. Regeneration capacity of leaf disks was compared to meristem-derived propagules in six strawberry cultivars. Direct shoot regeneration occurred in all tested cultivars with different frequencies depending on explant source. From GDH leaf disks, the cultivars Camarosa, Gaviota and Seascape produced the highest number of shoots/explant (38, 31 and 31 shoots, respectively). However, optimum number of shoots/explant from in vitro leaf disks was achieved in the cultivars Carlsbad, Chandler and Sweet Charlie (13.3, 12.6 and 12.3 shoots, respectively). In general, regeneration capacity of GHD leaf discs was more than two-folds of that obtained from in vitro leaf disks. The efficiency of meristem culture was intermediate between the above two systems. Rooted plantlets were successfully acclimatized under mist. The only morphological abnormality detected was a white streaked variant observed out of 456 Camarosa plants derived from meristem culture. SDS-PAGE of protein profile proved consistency in banding patterns of mother plants and those derived from direct regeneration or meristem proliferation.