An efficient in vitro propagation methodology for Annatto (Bixa orellana L.)

Efficient methods were developed for both in vitro seed germination and micropropagation of an economically important dye yielding multipurpose tree, Bixa orellana L. Mature seeds were inoculated onto Murashige and Skoog (MS) medium supplemented with different concentrations of gibberellic acid (GA3). Highest frequency of germination (93.3 %) was recorded on medium supplemented with 3 μM GA3 against 13.33 % in control. Nodal explants cultured on MS medium fortified with 5 μM isopentanyl adenine (2-iP) produced maximum explants response (93.3 %) and highest number of shoots (35.71). Addition of relatively higher concentration (15 μM) of benzyl adenine (BA) resulted in the production of significantly (P < 0.05) reduced number of shoots (12.66). Sucrose at 87.6 mM was found to be the best carbohydrate source for multiple shoot induction compared to glucose and fructose. Regenerated shoots (3-4 cm) were rooted (95.5 %) on agar gelled MS medium supplemented with 10 μM indole-3-butyric acid (IBA). In vitro developed plantlets with well-developed roots were potted and acclimatized initially in the growth chamber and then moved to a green house with 83.3 % survival. The present protocol avoids the use of auxins in shoot multiplication medium, which will lower the cost, avoid callus formation and thus reduces the possibility of somaclonal variation in the regenerated plants. The method is efficient to produce over 32,000 hardened plants within a 10-month culture period starting from a single nodal explant.