Sustainable use of Cryptocoryne wendtii and Echinodorus cordifolius in the aquaculture industry of Sri Lanka by micropropagation
C. DISSANAYAKE, M. HETTIARACHCHI AND M. C. M. IQBAL
In the aquaculture industry of Sri Lanka, Cryptocoryne and Echinodorus species are important aquatic plants. In the absence of a regular supply due to lack of effective propagation methods, Cryptocoryne species are indiscriminately harvested from the wild to supply to the export market. The threat on the species is further compounded by the loss of their rainforest habitats. Out of the ten endemic Cryptocoryne species that occur in Sri Lanka, nine are classified as “Highly Threatened” species in the Red List of International Union for the Conservation of Nature. Echinodorus cordifolius is not found in the wild but is popular in aquaria. In order to overcome the problems of species loss and inadequate supply to the local and foreign markets, an in vitro micro-propagation method was developed for both these species. Due to the difficulty in obtaining axenic cultures from these species, rhizome segments were used to induce axillary bud growth and subsequent shoot multiplication. Shoot buds were induced from rhizome segments of C. wendtii cultured on a Murashige and Skoog (MS) basal medium supplemented with 11 – 133 µM benzyladenine (BA) and 13.4 µM naphthalene acetic acid (NAA). The induced shoots were separated after 21 days and sub-cultured twice every 14 days on MS medium, which increased the shoot multiplication. E. cordifolius responded positively to a combination of 24.6 µM N-isopentenyladenine (2iP) and 2.68 µM NAA, while 2iP alone did not induce shoots. Two sub-cultures at 14 day intervals increased the shoot multiplication. Rooting was induced in both species by culturing the shoots in ½ MS liquid medium with indole butyric acid (IBA). Acclimatization was done in a humid growth chamber for one week and the plantlets were gradually transferred to the green house. All the plantlets rooted and survived in the green house.