Effect of osmotic stress on in vitro propagation of Musa sp. (Malbhog variety)

In vitro propagation of banana preferably use sword sucker as explant source where microbial contamination poses a great problem in establishment of aseptic cultures. This study demonstrates up to 36% reduced microbial contamination in aseptic culture establishment and subsequent micropropagation due to osmotic stress induction in the banana suckers. Osmotic stress was induced by keeping the freshly collected suckers in shade and measuring fresh weight at 0, 7, 14, 21, and 28 days interval to ascertain loss of moisture. Stress induced for 21 days showed 58.85% moisture loss showing lowest contamination upto 40% against 76% for fresh suckers. Micropropagation of Musa sp. (Malbhog variety) through shoot tip culture of stressed suckers was carried out in Murashige and Skoog (MS) medium supplemented with 1 to 2 mg/l  6-benzyl-aminopurine (BAP), 2 to 4 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.5 mg/l  α-naphthalene acetic acid (NAA). Multiplication of plantlets was observed till 6th passage. From 19 aseptically established explants of 21 days stressed sucker sub cultured in MS medium fortified with 1.0 mg/l BAP and 0.5 mg/l NAA, for 6th passage produced 5122 plantlets. Regenerated micro shoots were rooted in MS medium fortified with 0.5 mg/l IAA. The plantlets were hardened in polybag containing soil and seasoned cow dung.   Key words: Osmotic stress, shoot tip culture, in vitro, Musa, Malbhog.