Role of tryptophan on in vitro rooting in microshoots of Azadirachta indica A. Juss (Neem)

Development of the root is a major step in the rapid propagation of plants under in vitro conditions. In the present study, an efficient and rapid protocol was developed for the in vitro regeneration of Azadirachta indica through axillary shoot proliferation in nodal segments collected from mature trees. For axillary shoot proliferation nodal explants were inoculated on MS medium supplemented with different concentration of BAP + additives. Maximum 100% axillary shoot proliferation with 3.95 number of shoot regenerated and 3.60 cm length of regenerated shoots was obtained on MS medium supplemented with BAP 8.88 µM. In vitro regenerated shoots were further multiplied on MS medium supplemented with different concentration of BAP + additives. Best shoot multiplication in terms of 4.80 number of shoot and 3.95 cm length of regenerated shoots was observed on MS medium supplemented with 4.44 µM BAP. For in vitro rooting, regenerated microshoots were cultured on MS medium supplemented with different concentration of tryptophan + additives. The highest rooting percent (100%), number of roots (10.30) and mean root length (6.33 cm) was observed on MS medium supplemented with 146.89 µM tryptophan within 7-8 days of inoculation. The in vitro rooted plantlets were successfully hardened and acclimatized in poly house. These plants showed a good survival rate of 95% under field conditions