Somatic embryogenesis and shoot proliferation of Mussaenda cultivars

Midrib sections of Mussaenda 'Queen Sirikit', 'Dona Luz', and 'Dona Hilaria' were cultured on Murashige and Skoog medium (MS) supplemented with 87.7 mM sucrose, 5 g agar l(-1), 0, 5, 10 or 20 mu M indole-3-acetic acid (IAA) and 0, 0.5, 1, 2.5, 5, 10, 25 or 50 mu M 6-benzyladenine (BA). In addition, aseptic 5 mm shoot tips from 'Dona Luz' cultures were excised and cultured on MS basal salts, 0.6 mM myo-inositol, 1.2 mu M thiamine-HCl, 87.7 mM sucrose, 7 g agar l(-1), 0, 2.5, 5, 10, 20, or 40 mu M BA, 0 or 1 mu M alpha-naphthaleneacetic acid (NAA) and 0 or 217 mu M adenine sulfate at pH 5.8. Calluses began to develop after two weeks at the cut ends of midribs when cultured on a medium containing IAA. Somatic embryos first appeared at eight weeks but only on 'Queen Sirikit' callus. After 1 5 weeks the average number of somatic embryos produced per tube decreased as the IAA concentration increased from 0 to 20 mu M. BA concentrations between 5.0 and 10.0 mu M resulted in the largest number of somatic embryos per tube. After six weeks, the total, axillary and adventitious number of 'Dona Luz' shoots increased as the BA concentration in the culture medium increased from 0 to 20 mu M Average shoot length and fresh weight decreased from 0 to 40 mu M BA. The addition of NAA to the culture medium reduced shoot number. Adenine sulfate in the presence of RA reduced the total number of shoots An ideal medium fnr proliferating the largest number of 'Dona Luz' shoots would be a MS medium supplemented with 10-20 mu M BA.