In vitro clonal propagation of Holarrhena antidysenterica (L.) wall. Through nodal explants from mature trees

In vitro clonal propagation of 18-20-yr-old Holarrhena antidysenterica trees has been achieved by employing nodal explants. The tree explants showed marked seasonal variation in their morphogenic response under in vitro conditions. Maximum response was obtained from the beginning of May to the end of July, followed by a gradual decline, finally dropping to zero from October to February. The explants induced multiple shoots only on cytokinin-containing medium. Several cytokinins [N-6-benzyladenine (BA), N-6-(2-isopentenyl) adenine (2ip), 6-furfuryl aminopurine (Kn), and adenine sulfate (Ads)] were assayed. The best response was achieved with 15 mu M BA in which 62.5% of cultures produced 2.75 +/- 0.2 shoots per explant with 3.56 +/- 0.2 cm average length. Amongst the three heavy metals assayed, silver nitrate (AgNO3) significantly improved the response. This compound enhanced both the percentage of responding cultures (86.6%) and the average shoot number (4.73 +/- 0.2) at a concentration of 20 mg l(-1). Further improvement in the morphogenic response occurred when explants from in vitro shoots were employed instead of mature trees. In this case, the percentage of morphogenic cultures was increased to 100% at the third subculture with an average of 11.45 +/- 0.3 shoots per explant. Regenerated shoots were rooted in half-strength Murashige and Skoog medium with 10 mu M indole-3-acetic acid. The plantlets were successfully acclimatized in soil.