High frequency shoot regeneration through cotyledonary node explants of Bauhinia tomentosa L., a woody leguminous tree

Abstract

SummaryAn efficient in vitro method has been established for the production of whole plantlets of Bauhinia tomentosa using cotyledonary node (CN) explants excised from 15 d-old aseptic seedlings. Proliferating shoot cultures were obtained by placing CN explants on Murashige and Skoog (MS) medium supplemented with 6-benzyladenine (BA), kinetin (Kn), and 2-isopentenyl adenine (2-iP), singly or in combination, with either of the auxins, indole-3-acetic acid (IAA) or αnaphthalene acetic acid (NAA). MS medium augmented with 5.0 µM BA was found to be most effective in providing the highest frequency (84%) of shoot regeneration, associated with the maximum number of shoots (9.0 ± 0.6) per explant. The highest efficiency of shoot proliferation was observed using a combination of 5.0 µM BA and 0.5 µM NAA, where the number of shoots increased to 16.2 ± 0.2 per explant after 8 weeks of culture. Improved shoot multiplication and elongation rates were achieved when 20.0 mg l–1 adenine sulphate (AdS) was added to the combined treatment of 5.0 µM BA and 0.5 µM NAA, where an average shoot number of 17.0 ± 0.6 and an average shoot length of 5.8 ± 0.3 cm were obtained.The maximum frequency of root formation (70%) and greatest root lengths (2.3 ± 0.4 cm) were obtained on filter-paper bridges in liquid MS medium augmented with 2.5 µM IBA and 5.0 µM chlorogenic acid (a phenolic compound) after 4 weeks of culture. Regenerated plantlets were successfully acclimatised in a growth room and subsequently transferred to a greenhouse.This is the first report on in vitro plantlet regeneration in B. tomentosa using CN explants.