The objectives of this study were to clarify the distribution, habitats, host specificity and eco-physiological characteristics to apply in vitro tissue culture to develop conservation strategies on the endangered mistletoe species, Loranthus tanakae in Baekdudaegan, Republic of Korea.

One thousand three hundred and eighty five units of L. tanakae, 480 host trees were analyzed through this study where the altitude was distributed to 353～1,250m at ridges of mountains where maximum sunlight was observed. The host trees of L. tanakae which was composed of 5 families, 6 genera, 9 species, 1 subspecies, were observed as Betulaceae : Betula davurica, Betula schmidtii, Carpinus laxiflora, Fagaceae : Quercus mongolica, Quercus serrata, Quercus dentata, Quercus variabilis, Ulmaceae : Ulmus davidiana var. japonica, Rosaceae : Prunus sargentii Aceraceae : Acer pseudosieboldianum. Maximum parasiticism on Quercus mongolica was at 81.5% (389 trees among 480 host trees). The average DBH of host tree was 38.6cm whereas the attached height of the host tree was 12.9m. Twig death caused by the attachment of L. tanakae was found in 339 host trees (70.6% total 686 branches) among the 480 host trees analysed. Most of the population and the distribution of L. tanakae were highly affected by DBH of the host tree.

The leaf feature of L. tanakae was an oval shape that is resembling a scoop whereas those of Viscum album var. coloratum and V. album for. rubroauranticum were lanceolate. The seeds of L. tanakae were longer ovals than those of the seeds of V. album var. coloratum and V. album for. rubroauranticum. The maximum photosynthetic rate of L. tanakae was 9.36 μmol？m-2s-1 in June whereas the maximum evaporation was 5.06 mmol？m-2s-1 in July. The value of Fv/Fm which represents stress index recovered in June and was maintained at 0.8 but dropped dramatically after September. The chlorophyll contents of L. tanakae by season were the highest in July, with chlorophyll a at 6.25 and chlorophyll b at 1.97.

A factorial experiment of in vitro tissue culture evaluated the effects of seed storage duration (0, 8, 16 weeks), media (MS, SH, White, WPM), presence of viscin, GA3, concentration as well as type of gelling agent. Seeds germinated after a week culture in in vitro condition produced radicles. In vitro seed germination was optimal in SH medium (69%) with the addition of 0.35% gelrite (75%) with the seeds removed viscin. As seed storage duration was increased to 8 or 16 weeks, the in vitro seed germination rate reduced rapidly and holdfasts were also produced at the side of radicles. White medium without any supplements was an optimal condition for producing holdfast and haustorium at 98% and 8% respectively. Process of in vitro germination of L. tanakae was followed to radicle elongation, holdfast development and haustorium formation sequentially. In addition, the callus of L. tanakae was capable of surviving up to 40 weeks when placed in white medium where NAA, BA and CH were added in the medium.

L. tanakae was evaluated as VU (EN) grade, 5th grade, Ⅰst grade and protected species by law with the results being evaluated using the evaluation parameters endangered species standardized by the National Arboretum of Korea Forest Service (2008) and Ministry of Environment (1997; 2011b), National Institute of Environmental Research, Ministry of Environment (2006) based on the report of this survey.

Major causes to be threatened L. tanakae populations were illegal collection by human activity and competition between V. album var. coloratum and L. tanakae. L. tanakae showed be designated as an endangered species (EN) based on this study. Efficient in situ and ex situ conservation measures were determined as follows : the plant’s distribution sites Mt. Seorak, Mt. Taegi and Mt. Odae should be designated as the protected areas for forest genetic resources as well as conservation activities with high priority. Particularly, as relevant research is to preserve L. tanakae in the designated area, a study on ex situ conservation should be forwarded in connection with a study on in vitro tissue culture, in order to improve the success of ‘taking root’ and reducing germination time. Hence, the conservation of the plant must be carried out at the level that transplants into the protected area so that genetic diversity is secured. However, several incomplete tasks such as the environmental factors that affect the distribution of L. tanakae (soil, flora, humidity, temperature), and the effect of birds on the distribution of the plant, should be considered in order to understand the life history of L. tanakae for proper conservation of the species.