In vitro optimization of seed germination and protocorm development in Gastrochilus japonicus (Makino) Schltr. (Orchidaceae)

Gastrochilus japonicus (Makino) Schltr. is one of the endangered species in Japan. The aim of this study was to establish an ex-situ conservation method of this species through asymbiotic culture of seeds using media with defined substances without using plant growth regulators. We investigated the influences of different media (New Dogashima, Murashige and Skoog, Modified Knudson C and Modified Vacin and Went), seal materials (surgical tape: not air tight, and Parafilm & REG; M: air tight) for culture vessels, several kinds of carbohydrates (sucrose, maltose, trehalose and glucose), and addition of activated charcoal. The results showed that New Dogashima (ND) medium supplemented with 29.2 mM trehalose was suitable for seed germination (71.9% Parafilm & REG;, 57.5% surgical tape) and subsequent protocorm development. Seal materials for culture vessels with different aeration properties did not affect seed germination. Moreover, ND medium containing 58.4 mM sucrose and 1 g/l activated charcoal was favorable for the plantlet growth after induction of leaves from protocorms. In contrast, ND medium containing trehalose showed slow growth after leaf induction from protocorms among all the carbohydrates tested although it gave the lowest necrosis rate. In seed germination and seedling growth of Gastrochilus japonicus, it might be useful to use media containing trehalose until protocorm formation stage and those containing sucrose and activated charcoal for the stage after leaf induction from protocorms.

Automated summary

The aim of this study was to establish an ex-situ conservation method for Gastrochilus japonicus using media with defined substances without plant growth regulators. The results showed that New Dogashima medium supplemented with 29.2 mM trehalose was suitable for seed germination and subsequent protocorm development. Moreover, ND medium containing 58.4 mM sucrose and 1 g/l activated charcoal was favorable for the plantlet growth after leaf induction from protocorms.