Factors influencing In Vitro establishment of mango shoot buds

Mango shoot bud explants taken directly from the field grown mature tree face major problems of phenolic exudation and deep seated contamination in establishment of aseptic cultures. Due to these problems, the explants do not survive long enough to respond to culture conditions. The problems of phenolic exudation and microbial contamination were overcome using various sequential pretreatment and different sterilizing agents. The shoots were defoliated in the field and sprayed with disinfectant solution (0.1% bavistin + 0.1% gentamycin) followed by spray of 2 mg/l BA + 2 mg/l GA₃ every alternate day upto 15 days. The shoots were collected in antioxidant solution (ascorbic acid 70 mg/l + citric acid 50 mg/l) and kept for 30 min. followed by running tap water treatment for two hours and stirring in PVP (0.5%) for 1 hour. This was followed by sequential sterilization with 2–3 drops of Tween-20 in distilled water for one hour followed by rinsing with 70% alcohol for 30 seconds and 0.1% HgCl₂ treatment for 12–15 min. before inoculating on medium. Sub culturing into fresh medium was done on every alternate days up to one week and then weekly. Using these methods 80% sterile cultures were obtained which remained green for 8–10 weeks on MS basal medium supplemented with 3 mg/l indole acetic acid + 1 mg/1 kinetin + 200 mg/l adenine sulphate + 1 mg/l thiamine + 1 mg/l riboflavin + 100 mg/l casein hydrolysate + 400 mg/l glutamine + 100 mg/l PVP + 100 mg/l ascorbic acid + 60 mg/l sucrose. Shoot buds of cv. Amrapalli showed the best response with 48.92% cultures remaining green with opening of leaf primordial even after 4 weeks to inoculation. Differentiation of shoot buds into plantlets was achieved but plantlets did not grow beyond 3–4 leaf primordial stage.