Factors Affecting on Induction of Microrhizomes in Ginger (Zingiber officinale Rosc.), Cultivar Local from Sri Lanka

Abstract

Aims: In-vitro produced microrhizomes in ginger are favored as planting material over other conventional planting materials as they are free from soil born pathogens. This study was conducted to develop an efficient protocol for production of healthy microrhizomes including the investigation of effect of different growth regulators, sucrose concentration and photoperiod exposure levels. Place and Duration of Study: The entire study was conducted in plant tissue culture research unit of the Department of Export Agriculture, Walpita, Sri Lanka between November 2013 and August 2015. Methodology: In-vitro produced shoots established in hormone free medium were cultured in Murashige and Skoog (1962) (MS) medium fortified with eight treatments of 6-benzylaminopurine (BAP) (0.0, 2.0, 0.4 and 6.0 mg L-1 of BAP) and Naphthalene acetic acid (NAA) (0.1 and 0.2 mg L-1 of NAA) structuring in factorial design to study the effect of growth regulators for formation of microrhizomes. In-vitro produced shoots were cultured on MS medium fortified with different concentration of sucrose (30, 60, 90 and 120gL-1) separately. Effect of the solid/liquid nature of the medium and the different photoperiod level on induction of microrhizome was also studied.  Results: Results revealed that medium containing 4.0 mgL-1 BAP with 0.1 mgL-1 NAA showed the best response followed by 6.0 mgL-1 BAP with 0.1 mgL-1 NAA for induction of microrhizomes within 60 days. Increased level of NAA did not enhance mocrorhizome induction. Results of different concentration of sucrose revealed that MS medium fortified with 90 g L-1sucrose recorded the highest fresh and dry weight of microrhizomes followed by the treatment with 60 g L-1 sucrose. However, plantlets supplemented with more than 90 g L-1 of sucrose exhibited lower weight of microrhizomes, but higher root induction and root fresh weight probably due to accumulation of water. Different photoperiod exposure levels revealed that 16 hrs of light and 4 hrs of dark condition with solid medium produced highest fresh weight (3.72 g) and highest number of microrhizomes (9.6). Conclusion: Murashige and Skoog (1962) medium supplemented with 4 mgL-1 BAP, 0.1 mgL-1 NAA and 90 gL-1 sucrose in solid form with 16-h photoperiod for 10 weeks of culture duration were the best conditions for induction microrhizomes in ginger, cultivar Local.