• Meristem tips;
  • micropropagation;
  • nodal segments;
  • Populus;
  • shoot development;
  • shoot tips

Twelve commercial clones of poplar were cultured in vitro from meristem lips (0.3–0.5 mm diameter), shoot tips (4–6 mm long) and nodal segments (5–10 mm long). Shoot-producing cultures were obtained from 4, 32 and 70% of meristem lips, shoot tips and nodal segments within 12, 6 and 4 weeks, respectively. The genotype of cultures had a greater influence on development of shoot-producing cultures than medium composition. Cultivars Max/Ber and Oxford had the highest rates of establishment in culture and subsequent shoot proliferation, while P. tacamahaca, P. trichocarpa and cv. Robusta exhibited very low rates of establishment and low vigor in vitro. Shoot tip development was best on agar-solidified medium whereas liquid medium resulted in vitrification. Higher rates of axillary shoot production from established cultures were obtained with benzyladeninc or zeutin than with 2-isopen-tenyladenine. deducting the benzyladenine concentration from 4,4 to 1.1 μM, increased the production of elongated shoots suitable for rooting.