CONTRIBUTION OF PHOTOSYNTHESIS TO DRY WEIGHT INCREASE OF IN VITRO POTATO CULTURES UNDER DIFFERENT CO2 CONCENTRATIONS

Vigorous Growing of Donor Plantlets by Liquid Overlay in Subcultures Is the Key to Cryopreservation of Endangered Species Pogostemon yatabeanus

Cryopreservation is a unique option for the long-term conservation of threatened plant species with non-orthodox or limitedly available seeds. However, the wide application of cryopreservation for the protection of wild flora is hampered by some reasons: limits of source material available, difficulties in in vitro propagation, needs to re-optimize protocol steps for new species, etc. In this study, using an endemic and endangered Korean species, Pogostemon yatabeanus, we investigated subculture medium and supplements on in vitro growth of donor plants: medium strength, gelling agents, liquid overlay, plant hormones, and activated charcoal. Subculture conditions of each cycle tested significantly impacted on height and dry weight of subcultured donor plantlets. Among the treatments tested, the overlay of the liquid medium on top of gellan gum-gelled medium significantly increased the growth of shoots and roots. In the droplet-vitrification procedure, the survival and regeneration of cryopreserved shoot tips were critically impacted by the dry weight of donor plantlets (CORELL = 0.85~0.95) which was affected by the following subculture conditions. Moreover, every subsequent subculture cycle before cryopreservation positively or negatively impacted post-cryopreservation regeneration. This study highlights the vigor of donor plantlets for post-cryopreservation regeneration and provides practices for the revitalization of donor plants during subcultures.

Development of an autotrophic culture system for the in vitro mycorrhization of potato plantlets

An autotrophic culture system was developed for the in vitro mycorrhization of potato plantlets. Roots of micropropagated plantlets were associated to an arbuscular mycorrhizal fungus under in vitro conditions, while shoots developed under open air conditions. Several thousand spores, an extensive extraradical mycelium and an abundant root colonization were obtained. Spores were able to colonize new plantlets under the same conditions. These results support the capacity of the autotrophic culture system to continuously culture arbuscular mycorrhizal fungi and may serve as a powerful tool to investigate various aspects of the symbiosis for which a source-sink relationship and photosynthetic active tissues are necessary.