Nutrient alginate encapsulation of nodal segments of Althaea officinalis L., for short-term conservation and germplasm exchange

Abstract

In the present study, an alternate method for germplasm storage in the form of artificial seeds was standardized via nodal explants excised from in vitro proliferated shoots. The explants were encapsulated using sodium alginate and calcium chloride as gelling matrix. For development of root along with shoot, excised nodal segments were pretreated with ½ MS medium along with 20 μM IBA for 24 h and encapsulation was carried thereafter. Combination of 3% sodium alginate augmented with 100 mM CaCl₂.2H₂O was found appropriate for the formation of clear and uniform beads and subsequent conversion of encapsulated nodal segments into plantlets. Maximum (66%) encapsulated nodal segments were converted into plantlets on MS medium supplemented with 7.5 μM BA and 0.5 μM NAA after eight weeks. Regeneration frequency of auxin-pretreated encapsulated and non-encapsulated nodal segments (stored at 4 ºC) was evaluated at different storage time (0 to 6 weeks). After four weeks of storage, encapsulated propagules exhibited highest conversion response on the optimized medium after eight weeks of culture. Plantlets were hardened and established with success in ex vitro conditions. Conversion of synthetic seeds into plantlets was observed when these were directly sown in autoclaved Soilrite^TM (Keltech Energies, Bangalore, India).

Keywords:

• Encapsulated nodal segments
• Indian medicinal plant
• germplasm conservation
• plantlet
• regeneration

Abbreviations:

• BA, 6-Benzyladenine
• IBA, Indole-3-butyric acid
• 2-iP, 2-isopentenyladenine
• Kn, Kinetin
• MS, (Murashige and Skoog, 1962)
• NAA, α-Naphthalene acetic acid
• PGRs, Plant Growth Regulators
• TDZ, Thidiazuron

Acknowledgement

The authors extend their appreciation to the International Scientific Partnership Program (ISPP) at King Saud University for funding this research work through ISPP # 0082. RN is grateful to the University Grants Commission, New Delhi, for the award of Dr DS Kothari Postdoctoral Fellowship. Award of UGC-BSR Faculty Fellowship to MA is duly acknowledged.