High-efficiency regneration in vitro from potato petioles with intact leaflets

The shoot/plantlet regeneration in vitro of seven potato (Solanum tuberosum L.) cultivars from petioles with intact leaflets was assessed using six tr eatment combinations - a basal medium with or without silver thiosulphate ( STS) or thidiazuron (TDZ) at two concentrations (2 or 0.5 mg/l) of the indo leacetic acid (IAA). The basal medium consisted of Murashige and Skoog (IMS ) salts and vitamins supplemented with 3 mg/l 6-benzylaminopurine, and 1 mg /l gibberellic acid, 30 g/l sucrose, and 7.0 g/l PHY-TOAGAR. TWO full sets repeats and one partial set repeat of independent experiments were conducte d and all produced similar results. Silver thiosulphate decreased the regen eration frequency and number of shoots peer callus. No significant changes were observed with thidiazuron. Regeneration rates of (100%) with up to 20 shoots/plantlets per callus were achieved at 2 mg/l IAA with cultivars Desi ree, Kennebec, Niska, and Lenape. These cultivars still showed high regener ation rates (87%-98%) on media with 0.5 mg/l IAA, and good regeneration rat es were also achieved by the other three cultivars (48%, 94%, and 50% for C hieftain, Russet Burbank, and Shepody, respectively). Even with the single medium protocol (0.5% IAA without thiosulphate or thidiazuron), Desiree, Le nape, and Niska exhibited a regeneration rate of 98%. The use of petiole-wi th-leaflet explants could be ideal for the regeneration step of potato gene tic transformation protocol because of their high regeneration efficiency a nd their small cut surface area for Agrobacterium elimination after co-incu bation.