ISSR markers endorsed genetically stable plants regeneration of neem (Azadirachta indica A. Juss.) through indirect organogenesis using different explants.

BACKGROUND: Various parts of neem (Azadirachta indica) have high demand in several industries. However, the inadequate supply of sources hampers the commercialization of different neem products. In this scenario, the current research was undertaken to produce genetically stable plants through indirect organogenesis. METHODS AND RESULTS: Several explants like shoot tips, internodal segments, and leaves, were cultivated on MS media with different growth regulators. Maximum callus formation was achieved using 1.5 mg/L NAA, 0.5 mg/L 2,4-D and 0.2 mg/L both for Kn and BAP in combination with shoot tip (93.67%). These calli showed an organogenic potentiality on MS medium having coconut water (15%) without growth regulators. This medium along with 0.5 mg/L Kn and 0.1 mg/L both for BAP and NAA yielded the maximum adventitious shoot production with shoot tip-derived callus (95.24%). These calli further produced the most buds per shoot (6.38) and highest average shoot length (5.46 cm) with 0.5 mg/L both for BAP and Kn and 0.1 mg/L NAA in combination after the fifth subculture. The 1/3 strength of MS media was found to be best along with 0.5 mg/L IBA and 0.1 mg/L Kn in combination to generate maximum root response (92.86%), roots per shoot (5.86) and longest average root length (3.84 cm). The mean plant survival after initial hardening was 83.33% which increased to 89.47% after secondary hardening. The lack of variation in ISSR markers among the regenerated trees is evidence of clonal fidelity between hardened plants. CONCLUSIONS: This protocol will accelerate the propagation of neem for utilization of its sources.