Determination of the Best Culture Medium and Plant Growth Regulators for Micropropagation of Neem Tree (Azadirachta indica A.Juss)

Azadirachta indica is a tree with high medicinal value that is conventionally propagated by seed while exhibiting heterozygosity. The aim of this research was to determine the best culture media and plant growth regulators for the micropropagation of Neem. Lateral and terminal buds of A. indica were sterilized with 0.15% and 0.2% mercuric chloride for 10, 11, 12, and 13 min, followed by washing with sterilized double-distilled water three times. At the proliferation and elongation stage, WPM and MS media were tested with different concentrations of BAP either alone or in combination with 0.01 mg L-1 IBA. LS and MS media containing four different levels of IBA (0, 0.5, 1.0, and 2.0 mg L-1) were used for the rooting stage. Pulsing technique with different IBA concentrations was investigated at the rooting stage. Hardening of rooted plantlets was done in potting soil containing peat and perlite (2:1), at 23-24 °C prior to transfer into the natural environment. Maximum survival percentage (70.83%) with minimum browning (10.42%) was achieved by sterilizing the explant with 0.15% of mercuric chloride at all times. The longest shoots (3.66 cm) were observed in the media containing BAP (0.5 mg L-1). Furthermore, the highest number of leaves (14.2 leaves per plant) was recorded in MS medium. Additionally, the MS media containing BAP hormone alone at 0.7 mg L-1 produced the highest number of shoots (3.6 shoots per treatment). LS medium supplemented with IBA (4.0 mg L-1) using the pulsing technique gave the best result at the rooting stage.