Efficient In-Vitro Micropropagation Of An Endangered Marsh Species Ranalisma Rostratum Through Organogenesis Of Buds And Stolons

Ranalisma rostratum, a marsh plant species, is considered to be extinct in China because the wild population had not been discovered till 1930s. In 1993, R. rostratum was rediscovered in Chaling, Hunan Province, and is under people's supervision and preservation. In this study, an efficient system was established to preserve this species through In vitro micropropogation through an orthogonal analysis (L-16 (4(4))) with four factors (6-benzylaminopurine, BA; kinetin, KT; zeatin, ZT; and indolebutyric acid, IBA) at four levels. Four indexes (bud induction rate (BIR), shoot proliferation (SP), shoot height (SH), and shoot color (SC)) were recorded to select the optimum combinations of the hormones. The results showed that: (1) Buds are only induced from stem segments. (2) Three cytokinins (BA, KT and ZT) and appropriate IBA promote the bud occurrence and shoot growth. (3) The growth vigor is improved by ZT, but inhibited by high concentrations of BA and KT. (4) The plantlets produce stolons with novel rooted plants in MS medium without any hormone. Therefore, the optimum bud-induction, shoot recovery, and shoot-proliferation mediums are 2 mg.L-1 BA + 2 mg.L-1 KT +0.2 mg.L-1 ZT + 0.5 mg.L-1 IBA, 1 mg L-1 BA + 0.4 mg L-1 ZT+0.25 mg L-1 IBA and 3 mg.L-1 BA +3 mg.L-1 KT + 0.4 mg.L-1 ZT, respectively, and the optimum root-induction and stolon proliferation medium is MS without hormone.