Propagation of Dalbergia sissoo Roxb. through in vitro shoot proliferation from cotyledonary nodes
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A protocol is presented for micropropagation of an economically important timber-yielding forest tree, Dalbergia sissoo Roxb. (Sissoo). Multiple shoots were induced from cotyledonary nodes derived from 1-week-old axenic seedlings on Murashige and Skoog's medium containing either N6-benzyladenine (BA), kinetin (Kn), isopentenyladenine (2iP) or thidiazuron (TDZ), with BA being the most effective growth regulator. High-frequency shoot proliferation (99%) and maximum number of shoots per explant (7.9 shoots) were recorded with BA at an optimum level of 8.9 μM. Concentrations of all cytokinins tested above the optimum level markedly reduced the frequency of shoot proliferation. A proliferating shoot culture was established by repeatedly subculturing the original cotyledonary node on shoot multiplication medium after each harvest of the newly formed shoots. Primary shoots were multiplied as nodal explants, and from each stem node 2 or 3 shoots developed. Thus, 60–70 shoots were obtained in 3 months from a single cotyledonary node. About 91% of the shoots developed roots following transfer to half-strength MS medium containing a combination of 5.7 μM indole-3-acetic acid, 4.9 μM indole-3-butyric acid and 5.3 μM indole-3-propionic acid. Eighty percent of the plantlets were successfully acclimatized and established in soil.
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