Micropropagation of an adult tree-<i style="">Wrightia tinctoria</i>

Abstract

Multiple shoots were induced <i style="">in vitro</i> from nodal shoot segments of a 30-yr-old plus tree having enhanced axillary branching. Initiation of culture was strongly influenced by the nature of explant and the season of harvesting. Nodal segments (91%) from young lateral branches produced an average of 5 shoots per node in 3 weeks on agar solidified MS medium supplemented with 2.0 mg l^-1 benzylaminopurine (BAP). After establishment of cultures and initiation of shoot buds, a cluster of shoots including mother explant, was transferred to medium containing a lower concentration of BAP (1.0 mg l^-1). A three-fold rate of shoot multiplication during every subculture of 3 weeks was achieved. Nodal segments from <i style="">in vitro</i> raised shoots were also used to initiate a new culture cycle. The shoots could be multiplied for at least 24 months without loss of vigour. The shoots (71%) were successfully rooted when their lower ends were dipped in pre-autoclaved indole-3-butyric acid solution (100 mg l^-1) for 10 min followed by their implantation on modified MS medium (major salts reduced to 1/4 strength) containing 200 mg l^-1 activated charcoal. Out of 2000 plants, 1600 (80%) were successfully hardened under greenhouse conditions and more than 200 have been planted out in soil where they are growing well.