SHOOT REGENERATION FROM LEAF TISSUES OF PHLOX-PANICULUTA L

A highly efficient shoot regeneration system from greenhouse-grown lea f tissues of Phlox paniculata cvs. Franz Schubert and Prospero was dev eloped. In a preliminary experiment, both TDZ and BA (at 5 mu mol/L ea ch) along with 2.5 mu mol/L IAA, induced almost a 100% regeneration fr equency for both genotypes, especially when explants were grown withou t any dark treatment. Moreover, significant differences were observed in regenerability of explants collected from first, second, and third nodes. In a factorial experiment with four BA or four TDZ levels (0.25 , 1, 3, and 5 mu mol/L) along with three IAA levels (0, 0.5 and 1.0 mu mol/L), <Franz Schubert> leaf explants exhibited significant differen ces in shoot organogenesis (mean number of sites of organogenesis/expl ant, callus development, % explants with >6 shoots/explant) and overal l quality of shoot regenerants (mean length of longest shoot, hyperhyd ration). Results of a principal component analysis indicated that, ove rall, BA was more effective than TDZ in inducing more shoots and more regeneration sites per explant, and with less callus development. Howe ver, hyperhydration (vitrification) of shoot regenerants on media cont aining 1 mu mol/L BA and 0 or 0.5 mu mol/L IAA prevented further elong ation of these shoots. In another factorial experiment, low levels of both BA (0.5 to 1.5 mu mol/L) and IAA (0 to 1 mu mol/L) were also inve stigated. It was observed that all shoot organogenesis occurred along the cut margins of leaf segments and without an intervening callus sta ge when explants were grown on an MS medium supplemented with 0.5 mu m ol/L BA and 0.5 mu mol/L IAA. Elongation of shoot regenerants was achi eved when these were transferred to an MS medium without growth regula tors.