Efficient micropropagation and rooting of king white mulberry (Morus macroura Miq.) var. Laevigata from nodal explants of mature tree

摘要

In the present study, nodal explants from mature trees were used for axillary shoot proliferation and rooting of Morus macroura. Nodal explants (1.5cm long) were cultured in MS medium supplemented with different levels of N6-benzyladenine (BA: 2, 4, 8, 10 or 12μM) and 1-nephthaleneacetic acid (NAA: 2 or 3μM for each). The rate of bud break was 100% at 10μM BA in combination with either concentration of NAA (2 or 3μM) after 6 days of culture. Generally, the length of axillary shoots was significantly improved by increasing the level of BA with auxin. Most of the nodal explants (60.2%) developed surface calluses on the aerial portions of explants at comparatively lower BA levels (2-4μM). The elongating axillary shoots were cut to prepare further nodal explants for multiple shoot induction. MS medium supplemented with BA (8.8μM) and 2μM indole-3-butyric acid (IBA) was quite effective for 65% shoot induction with 4.7 mean number of shoots and 8.4mm shoot length, after a week. Rooting was highest (85.6%) in half strength MS medium supplemented with 4 μM IBA and activated charcoal (0.1%) after 25 days. The number of primary (2.8) as well as secondary roots (10) was also highest on this medium with a mean root length of 7cm. The rooted shoots were acclimatized and transferred to field conditions. We concluded that nodal explants from mature trees can be manipulated in vitro for clonal multiplication of king white mulberry.