• Journal of Plant Biotechnology
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• v.37 no.4
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• pp.343-356
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• 2010

Plant micropropagation techniques include bud cultures using apical or axillary buds, organogenesis through callus culture or adventitious bud induction, and somatic embryogenesis. In Korea Forest Research Institute (KFRI), the first tissue culture trial in woody plant was initiated from the bud culture of hybrid poplars (Populus alba x P. glandulosa) in 1978. Since then several mass propagation techniques have developed from conifer and hardwood species, resulting in allowing practical application to Poplars, Birches and some oak species. In addition, useful micropropagation and genetic resources conservation techniques were established in some rare and endangered tree species including Abeliophyllum distichum. Among various in vitro propagation techniques, somatic embryogenesis is known to be the most efficient plant regeneration system. Since the first somatic embryo induction was reported in Tilia amurensis by KFRI in 1986, various protocols for direct or indirect somatic embryogenesis systems have developed in conifer and hardwood species including Larix leptolepis, Pinus rigida x P. taeda F1, Kalopanax septemlobus and Liliodendron tulipifera, etc. However, most of these technologies have been developed using juvenile tissues, i.e. immature zygotic embryos or mature embryos. Therefore it has been difficult to directly application to tree breeding program due to their unproven genetic background. Recently remarkable progresses and new approaches have been achieved in mature tree somatic embryogenesis. In this article we reviewed several micropropagation techniques, which have been mainly developed by KFRI and recent international progresses.

• Journal of Ginseng Research
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• v.48 no.2
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• pp.220-228
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• 2024

Background: Panax ginseng, one of the valuable perennial medicinal plants, stores numerous pharmacological substrates in its storage roots. Given its perennial growth habit, organ regeneration occurs each year, and cambium stem cell activity is necessary for secondary growth and storage root formation. Cytokinin (CK) is a phytohormone involved in the maintenance of meristematic cells for the development of storage organs; however, its physiological role in storage-root secondary growth remains unknown. Methods: Exogenous CK was repeatedly applied to P. ginseng, and morphological and histological changes were observed. RNA-seq analysis was used to elucidate the transcriptional network of CK that regulates P. ginseng growth and development. The HISTIDINE KINASE 3 (PgHK3) and RESPONSE REGULATOR 2 (PgRR2) genes were cloned in P. ginseng and functionally analyzed in Arabidopsis as a two-component system involved in CK signaling. Results: Phenotypic and histological analyses showed that CK increased cambium activity and dormant axillary bud formation in P. ginseng, thus promoting storage-root secondary growth and bud formation. The evolutionarily conserved two-component signaling pathways in P. ginseng were sufficient to restore CK signaling in the Arabidopsis ahk2/3 double mutant and rescue its growth defects. Finally, RNA-seq analysis of CK-treated P. ginseng roots revealed that plant-type cell wall biogenesis-related genes are tightly connected with mitotic cell division, cytokinesis, and auxin signaling to regulate CK-mediated P. ginseng development. Conclusion: Overall, we identified the CK signaling-related two-component systems and their physiological role in P. ginseng. This scientific information has the potential to significantly improve the field-cultivation and biotechnology-based breeding of ginseng.

• Journal of Korean Society of Forest Science
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• v.76 no.4
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• pp.370-375
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• 1987

This study was conducted to examine the position effect of axillary buds on shoot multiplication and rooting with 1-year-old seedlings of Quercus acutissima. Shoot multiplication was greatly affected by axillary bud position: Productivity of multiple shoots were decreased in the order of top, mid and basal explants respectively. The best shoot multiplication (mean 6.1 shoots per explant) was obtained on WPM medium containing $1.0mg/{\ell}$ BAP and $0.1mg/{\ell}$ NAA using basal explant after 4-week-culture. Rooting was also greatly influenced by position. Its percentage was increased in the order of top, mid and basal explant respectively. Root initiation was better and more rapid on 1/2MS medium than GD medium. High rooting percentage (100%) was obtained on 1/2MS medium containing $0.2mg/{\ell}$ IBA after 15 days culture. Sucrose concentrations did not effect on rooting. However root development and shoot growth were greatly affected by them. Root was developed shortly on 1-2% levels and shoot growth was getting retarded, whereas both of them did not show significant difference at 3-6% levels. Rotting was decreased on 7-8% levels gradually, but shoot and leaf condition was better than any other concentrations. Survival rate of rooted explants in pot was varied according to the position of explants. Seedlings of top part were survived up to about 50% but most of mid and basal part seedlings did not survive over 4 weeks even in high humidity condition. Seedlings in pots showed normal growth over 10 months but most of them showed the condition of premature leaf shedding.

• Horticultural Science & Technology
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• v.33 no.4
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• pp.501-510
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• 2015

In this study, we investigated the onset and release of endo-dormancy under natural conditions by observing bud break characteristics in 'Fuji' apple trees using water cuttings. Through examinations of bud break rate and days to bud break, we found that the endo-dormancy of 'Fuji' apple tree continues for 70 d from 165 to 255 d after full bloom (DAFB), from late October to early January of the following year. In addition, within 20 d of first bud break, based on a final bud break rate of 60% or more, we able to identify the timing of the changeover from para-dormancy to endo-dormancy, and endo-dormancy to eco-dormancy. Analysis of the chilling requirement during the endo-dormancy period revealed that chilling accumulation up to 255 DAFB to release endo-dormancy amounted to 666 and 517 h based on the CH and Utah models, respectively. Observation of internal changes in the bud during endo-dormancy showed that flower bud differentiation begins from mid-July, and t ime of inflorescence o f the disk f lower is a vailable to f ind. The f lower buds subsequently developed slowly but steadily during endo-dormancy and in the following year in February, the developmental stage of each organ had progressed. Moreover, the flower buds of 'Fuji' apples were mostly healthy during the dormancy period, but some exhibited necrosis of flower primordium, due partial cell damage from the formation of ice crystals rather than a direct effect of the low temperature. Flower buds were formed in both the axillary buds of bourse shoots and terminal buds of spurs, but lower bud differentiation was observed for the terminal buds of spurs at rate of about 65% of total buds, which was directly related to the bud size and shoot diameter.

• Journal of Forest and Environmental Science
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• v.35 no.4
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• pp.272-280
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• 2019

Forest medicinal resources, which constitute one of the non-timber forest products, have been regarded as healthy and highly valued products. To meet the increasing demand of the medicinal resources, it is necessary to improve the propagation methods of medicinal plants. In vitro propagation not only allows an opportunity for propagating plants in large numbers but also allows for enhancing the quality and quantity of the desired functional component of a plant by altering the growth factors, such as medium, carbon source, and plant growth regulators influence plant. There have been several studies of in vitro propagation methods, such as axillary bud culture, shooting, and embryogenesis, on Kalopanax septemlobus, Eleutherococcus sessiliflorus, Hovenia dulcis, and Schisandra chinensis in Korea between from 2000 through 2010. Furthermore, there have been attempts to proliferate callus and plantlets for producing useful natural compounds by using bioreactors. Here, we provide an account of the in vitro propagation methods of medicinal trees in Korea based on a review of several micropropagation studies.

• Korean Journal of Medicinal Crop Science
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• v.10 no.4
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• pp.249-252
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• 2002

Several plant growth regulators were examined for on their effect on the in vitro propagation of Kalopanax pictus$(T_{HUNB}.)$ $(N_{AKAI}.)$ on WPM medium. Among the cytokinins tested, BA at $13.32\;{\mu}M$ appeared to be the most effective for multiple axillary shoot formation. Although the addition of $2.89\;{\mu}M\;GA_3$ promoted stem elongation, it produced morphologically abnormal leaves and stems. For rooting of the shoots, $4.9\;{\mu}M$ IBA seemed to be more effective than $2.69\;{\mu}M$ NAA. When the regenerated plants were transferred on artificial mixture containing vermiculite and peat-moss (1 : 1, v/v), 81% of them survived and grew normally.

• Korean Journal of Plant Resources
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• v.28 no.3
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• pp.357-362
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• 2015

Carbohydrate sources are one of important factors associated with macro- and micro nutrients and phytohormones in vitro culture medium for shoot growth. The optimal carbohydrates for eight species of the genus Prunus which are economically important fruit crop was evaluated at the initiation and elongation stages. All carbohydrate seemed utilized for the bud break and leaf growth at the early stage of culture. However, shoot elongation and fresh weight of species tested were superior in the medium containing 90 mM of fructose or glucose rather than sucrose. There was no difference between glucose and fructose. Adventitious shoots from the axillary buds were induced in most species but no significant differences were observed except for two species (P. salicina ‘Shiro’ and P. tomentosa). These result demonstrated that glucose and fructose were suitable carbohydrate sources for diverse Prunus species than sucrose, although the response to the carbohydrates in the medium were slightly different in the species.

• Korean Journal of Plant Resources
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• v.11 no.3
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• pp.353-357
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• 1998

This study was conducted to determine the effect of growth regulators, genotype, and cutting position on the rooting and root growth from cutting of Chrysanthemum zawadskii H.. Rooting rate of Keungugeolcho in the treatement of IBA 500 and 1000 ppm was the better than those of other treatments of IAA, NAA and Rooton. Rooting rate differed depending on the genotype. Hangryobonggugeolcho was better than Keungucheolcho in rooting rate. The treatment of rooton remarkably induced many roots from the cuttings of eight accessions of Chrysanthemum zawadskii H.. Also, rooting rate and number of root differed depending on cutting position. When cuttings including shoot tip were cultured on tray containing bed soil, rooting rate and number of root induced from cuttings with shoot tip was higher than when cuttings without shoot tip and with lateral axillary bud were cultured.

• Korean Journal of Plant Resources
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• v.24 no.5
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• pp.591-598
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• 2011

This study was conducted to establish the tissue culture system for Atractylodes plant which is most frequently used in oriental medicine. Root and auxiliary bud of Dachul cv., which is Atractylodes hybrid (A. macrocephala x A. japonica), were used as target tissues for in vitro culture. In root culture, callus induction rate was higher in the treatment of BAP combined with NAA than others, however, 2-iP was more effective for callus proliferation and root induction. Although calli were effectively induced from the root and proliferated in lower concentration of cytokinin combined with higher auxin, root tissue was inappropriate for shoot regeneration. For plant regeneration with axillary bud, BAP combined with NAA was more effective than 2-iP with NAA or IBA. Number of regenerated plant per bud was 3.8, which was highest, and stem diameters was shown as 5.0mm under the conditions of 1 mg/L BAP combined with 1 mg/L NAA. Although, plant height was tend to be higher in 2-iP than BAP, number of the regenerated plant was lower via versus. Furthermore, root proliferation of regenerated plant was more effective in higher concentration of sucrose (7%) than in lower concentration (3%). In results, auxiliary bud was an efficient target tissue for producing regenerated plant of Atractylodes under the conditions of 1 mg/L BAP combined with 1 mg/L NAA and higher concentration of sucrose was effective for root proliferation of regenerated plants.

• Korean Journal of Agricultural Science
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• v.14 no.2
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• pp.205-212
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• 1987

To examine the morphogenetic response, stem segments of 8 Populus spp. and 3 different explants of P. nigra var. italica were cultured on MS (Murashige and Skoog 1962) and WPM (Woody Plant Medium) medium containing various phytohormones. The results obtained were as follows: 1. Shoot regeneration and development from stem segment of 8 Populus spp. showed a quite difference according to the section and the species. All of the species of Leuce and Tacamahaca section did not form adventitious buds, while most of explants showed axillary or dormant bud elongation after 4 weeks. But P. nigra var. italica of Aigeiros section showed a successful adventitious bud formation (mean 5.4 buds per explant). 2. Leaf, petiole, and internode segment of P. nigra var. italica showed a quite differences according to media and ex plants upon the morphogenetic response. Adventitious bud formation from leaf was more abundant and readily initiated on the abaxial side than on the adaxial side. Mean number of 103 adventitious buds per explant was obtained from abaxial side of leaf segment cultured on WPM medium containing $0.2mg/{\ell}$ BAP for 5 weeks. 3. 2,4-D (2,4-dichlorophenoxy acetic acid) supplemented to media appeared to be negative upon the adventitious bud formation of P. nigra var. italica, while it promoted callus formation from all explants. Especially, NAA (${\alpha}$-naphtalene acetic acid) or NAA combination with BAP (6-benzylaminopurine) promoted root regeneration from the all explant of P. nigra var. italica in this study.