EFFECTS OF THIDIAZURON AND BENZYLADENINE ON AXILLARY SHOOT PROLIFERATION OF 3 GREEN ASH (FRAXINUS-PENNSYLVANICA MARSH) CLONES

Mature seeds of three green ash (Fraxinus pennsylvanica Marsh.) clones , SD1009 (South Dakota origin), SD2002 (South Dakota origin), and KA20 18 (Kansas origin) were cut to remove the apical portion and germinate d on Murashige and Skoog (1962) salts with B5 vitamins (Gamborg et al. , 1968) (MSB5) medium without plant growth regulators. Stable axillary shoot establishment was achieved for all three crones by subculture o n MSB5 medium containing a combination of 5 mu M thidiazuron (TDZ), 5 mu M 6-benzyladenine (BA), and 1 mu M indole-3-butyric acid (IBA). Fol lowing shoot establishment, axillary shoots were placed on PI?SBS medi um containing a single treatment of TDZ (1, 5, 10, 20, or 40 mu M) or BA (1, 5, 10, 20, 40, or 80 mu M). Concentration of TDZ and BA signifi cantly affected shoot biomass (total dry weight of axillary shoots), w ith 10 mu m TDZ or 40 mu m BA providing maximum shoot proliferation wi th all three clones. Significant clonal differences also were noted in the proliferation of axillary shoots, with clone SD1009 exhibiting th e highest axillary shoot proliferation. Axillary shoots were rooted un der ex vitro conditions and acclimatized to the greenhouse.