Micropropagation of two endemic threatened Cryptocoryne species of Sri Lanka

Abstract

An efficient protocol was developed for the micropropagation of Cryptocoryne beckettii and Crypto-coryne bogneri, two endemic threatened aquatic herbs of Sri Lanka, highly valued as aquarium plants. Rhizomes of C. beckettii and C. bogneri were established on full strength Murashige and Skoog (MS) medium with 3% sucrose and regenerated shoots were cultured on MS medium supplemented with combinations of 6-benzylaminopurine (BAP) 2, 5, 8, 10 mg l-1 and 0.1 mg l-1 indole acetic acid (IAA) for multiple shoot regeneration. For root induction and shoot growth, agar solidified full and half strength MS medium and a soil-based medium were used. The presence of growth regulators in MS medium had a significantly high (p<0.05) effect on shoot multiplication in both species. Lowest mean number of shoots proliferated per shoot explant (C. beckettii 10.4 and C. bogneri 4.2) was observed in the absence of growth regulators. BAP alone or IAA alone in the medium also had no significant effect. Presence of both BAP and IAA in the medium significantly increased the shoot number. Highest mean number of shoots proliferated per single shoot explant (43.0) was observed in the combination of 5.0 mg l-1 BAP with 0.1 mg l-1 IAA for C. beckettii while the combination of 5.0 mg l-1 BAP with 0.1 mg l-1 IAA or 8.0 mg l-1 BAP with 0.1 mg l-1 IAA had highest mean number of shoots proliferation (51.8, 50.4) for C. bogneri. Mean number of roots induced per plant was highest (C. beckettii 8.4: C. bogneri 7.8) in the soil based medium consisting of a mixture of equal parts of 2 mm size ground brick fragments: sand: charcoal: top soil (medium A) with half strength MS and 0.1 mg l-1 NAA. Treatments of soil based medium had a significantly high effect on root and shoot development than the agar solidified media in both species. The plants were acclimatized with 90 % survival in C. beckettii and 100% survival in C. bogneri.