Enhanced Shoot Organogenesis in Bixa Orellana L. in the Presence of Putrescine and Silver Nitrate

An efficient protocol for direct shoot organogenesis
in Bixa orellana, known as achiote or annatto or
Latkhan (India), has been developed. Using nodal shoot-tip
explants, significant organogenetic responses, mean shoot
number and shoot elongation were observed when these
were incubated on Murashige and Skoog (MS) medium
containing 6.66 lM 6-benzyladenine (BA) and 4.9 lM
indole-3-butyric acid (IBA), and supplemented with either
200–1,500 lM putrescine or 40 lM silver nitrate (AgNO3).
Putrescine at 800 and 1,000 lM promoted the highest
mean shoot length and mean shoot number per explant,
respectively. Moreover, various concentrations of putrescine
induced callus development. Incorporation of a polyamine
biosynthesis inhibitor Difluro-Methyl Ornithine
(DFMO) inhibited in vitro shoot multiplication and also
altered the endogenous polyamine pool of B. orellana
shoots. The field survival of in vitro-derived plants of
putrescine and AgNO3 treatments was 70%. This protocol
can be used for improving the in vitro regeneration of
B. orellana for transformation studies.