Rapid in vitro multiplication of Melia azedarach L. (a multipurpose woody tree)

An efficient regeneration protocol for rapid multiplication of Melia azedarach, an economically as well as medicinally important timber-yielding tree, was developed. Nearly 90% of the culture exhibited axillary bud sprouting and multiple shoot formation from nodal segments derived from 20-year-old candidate plus tree on Murashige and Skoog (MS) medium supplemented with 5 mu M 6-benzyladenine (BA). The highest shoot regeneration frequency (92%), maximum number of multiple shoots (19.7 +/- A 0.31) as well as shoot length (4.9 +/- A 0.08 cm) was induced from nodal explants on MS medium amended with 5.0 mu M BA, 0.5 mu M indole-3-acetic acid (IAA) and 30 mu M adenine sulfate (AdS). Addition of 250 mg l(-1) ammonium sulphate, (NH4)(2)SO4, and 100 mg l(-1) K2SO4, prevented defoliation and tip burning without affecting the number of shoots. The explant harvest period also influenced the bud break and shoot sprouting from nodal segments. Repeated subculturing of nodal explants on fresh MS medium containing lower concentration of BA (2.5 mu M) along with IAA (0.5 mu M), AdS (30 mu M) and additives was found most suitable growth regulator regime for achieving 1.2-fold increase in shoot multiplication rate. The percentage of shoot multiplication as well as the number of shoots per node remained the same during first three subculture passages, afterwards a decline was recorded. About 90% of the in vitro regenerated shoots were successfully rooted ex vitro by giving a pulse treatment of 250 mu M indole-3-butyric acid for 15 min, followed by their transfer to thermocol cups containing soilrite. The raised plantlets were successfully acclimatized first under culture room conditions, then to green house with 85% survival rate.