Terpenoids are naturally occurring compounds involved in respiration, photosynthesis, membrane fluidity, and pathogen interactions and are classified according to the structure of their carbon skeleton. Although most terpenoids possess pharmacological activity, knowledge about terpenoid metabolism in medicinal plants is insufficient. Rehmannia glutinosa (R. glutinosa) is a traditional herb that is widely used in East Asia and has been reported to contain various terpenoids. In this study, we performed a comprehensive transcriptome analysis of terpenoid metabolism in R. glutinosa using two RNA sequencing platforms: Illumina and PacBio. The results show that the sterol, saponin, iridoid, and carotenoid pathways are active in R. glutinosa. Sterol and saponin biosynthesis were mevalonate pathway dependent, whereas iridoid and carotenoid biosynthesis were methylerythritol 4-phosphate pathway dependent. In addition, we found that the homologous genes of key enzymes involved in terpenoid metabolism were expressed differentially and that the differential expression of these genes was associated with specific terpenoid biosynthesis. The different expression of homologous genes encoding acetyl-CoA acetyltransferase, 3-hydroxy-3-methylglutaryl-CoA reductase, mevalonate kinase, mevalonate diphosphate decarboxylase, farnesyl pyrophosphate synthase, squalene synthase, and squalene epoxidase was associated with sterol and saponin biosynthesis. Homologous genes encoding 1-deoxy-D-xylulose 5-phosphate synthase were also differentially expressed and were associated with carotenoid and iridoid biosynthesis. These results suggest that the biosynthesis of specific terpenoids can be regulated by the homologous of key enzymes involved in plant terpenoid metabolism.

Background: Rehmannia glutinosa (Gaertn.) Libosch. ex Steud. has long been used as a traditional medicinal plant in Korea. This study was carried out to investigate the emergence conditions during the seedling periods in R. glutinosa. Methods and Results: The rhizomes of R. glutinosa variety (Jihwang 1) were harvested in the 22, March, 2018. The rhizomes were sown on in 50-cell plug trays. The emergence rates of seedlings at 15℃, 20℃, 25 - 40℃, and 45℃ treatment seedling were 1.3%, 96%, 100% and 0%, respectively. Rhizome rot was occurred at the temperature of 15℃ and 45℃. The emergence rates of seedlings in high moisture (HM), moderate moisture (MM) and low moisture (LM) treatments at 35℃ were 99.3%, 100%, and 0%, respectively. Drought damage was recorded in plant with the LM treatment. Seedling quality surveys were carried out at 10-days intervals from 10 to 60 days after sowing (DAS). Leaf length and leaf width were increasing until 50 DAS and the number of leaves was increasing until 60 DAS. Root length was increasing until 40 DAS, and then, flowering occurred from 30 to 60 DAS. Lastly, at 40 DAS, leaf aging and root enlargement was observed. Conclusions: We concluded that the emergence of seedlings was possible in the range of 20 to 40℃. Considering drying and rotting damage, we concluded that the moderate level of moisture is most appropriate for seedling emergence. In addition, we concluded that optimal seedling periods are between 30 and 40 DAS.

Background: Rehmannia glutinosa is a perennial herb belonging to the family Scrophulariaceae and is used in traditional oriental medicine. This study was conducted to evaluate the appropriateness of plug-seedling cultivation for replanting of R. glutinosa. Methods and Results: The seed rhizomes of Rehmannia glutinosa 'Jihwang 1' were harvested in the middle of March, 2018. Direct seedling cultivation was conducted after air curing for 3 days. The seedlings for transplanting were cultivated for 30 (30D), 45 (45D), and 60 days (60D). The mat formation rates of the 30D, 45D and 60D treatment seedling were 81.3%, 100%, and 100%, respectively. Of the tree treatment groups, flowering occurred only in the 45D and 60D treatment groups, and their flowering rates were $7.3{\pm}3.06%$ and $13.3{\pm}1.15%$, respectively. The agronomic characteristics and active components of the three treatment groups were evaluated in comparison with the DS1 (directly seeded group, control) and DS2 (directly seeded group, replanting) groups. As a result, the leaf length and leaf width of the 30D seedlings were higher than other treatment groups, but the number of leaves per plant was statistically the same. In addition, root diameter and yield of the 30D seedling were statistically the same as DS1. Moreover the catalpol contents of 30D, 45D, DS1 and DS2 group seedlings were 2.23%, 1.86%, 2.50% and 2.08%, respectively. Conclusions: Taken together, these findings suggest it is feasible to use the plug-seedling cultivation method for replanting of R. glutinosa. seedlings. However, further evaluation of the economic aspect is needed.

Background: There have been no studies to date on rhizome development and optimal harvest timing for Rehmannia glutinosa. We therefore, undertook this investigation. Methods and Results: R. glutinosa ‘Jihwang 1’ was sown in early May and harvested in early November. Growth investigations were carried out at intervals of 10 days between 90 and 180 days after sowing (DAS). Leaf length, leaf width, and number of leaves increased until 150 DAS but decreased after 160 DAS. Rhizome length increased until 120 DAS subsequently, rhizome diameter increased rapidly between 130 and 150 DAS. Thus, the key period for rhizome enlargement in R. glutinosa is thought to be 130 to 150 DAS. Fresh root yield increased sharply from 916 ㎏/10a to 1,914 ㎏/10a between 4 and 5 months after sowing (MAS). Dry matter ratio increased gradually from 19.2% at 4 MAS to 24.4% at 6 MAS. Finally, the level of catalpol, a key active ingredient, increased sharply from 0.41% to 4.21% between 5 and 6 MAS. Given the dry matter ratio, catalpol content and yield measured, we suggest that optimal R. glutinosa harvest time is 6 MAS. Conclusions: Based on our results, the key period for rhizome enlargement is 130 to 150 DAS and optimal harvest timing is 6 MAS. We anticipate that these and other results of this study can be used to inform cultivation of R. glutinosa.

Background: Licorice is an important medicinal plant, but climate conditions can hinder seed production. Because it is difficult to produce the seeds, Korea mostly depends on the imported product. In addition, when grown domestically, the standard ingredients do not comply with those of the Korean Pharmacopoeia (glycyrrhizin 2.5% and liquritigenin 0.7%). Therefore, it is necessary to develop licorice variety suitable for the domestic environment.BRMethods and Results: A new interspecific hybrid cultivar designated ‘Dagam’, was developed from Glycyrrhiza glabra × G. uralensis (G. korshinskyi Grig.) and is regarded as a high-yielding and high-quality licorice by Rural Development Administration. On average the yield for ‘Dagam’ was recorded 431.5 ㎏/10a. The cultivar displayed strong brown spot disease and lodging resistance. Additionally, the glycyrrhizin and liquiritigenin contents of ‘Dagam’ (3.0 and 0.7%, respectively) met, the Korean Pharmacopoeia standard. This cultivar can widely adapt to most cultivation areas in Korea except Jejudo, Gangwondo, and the mountain-alpine regions. Furthermore, ‘Dagam’ was not showed any cytotoxicity and high cell viability compared to ‘G. uralensis’.BRConclusions: The interspecific hybrid cultivar ‘Dagam’ will contribute to the stability of domestic cultivation of licorice in Korea.

Background: When the licorice cultivated in Korea, the quality index components are lower than the standard value, and physiological disorders occur frequently. Therefore, we evaluated the growth and yield characteristics of resources to develop licorice varieties suitable for the domestic environment.BRMethods and Results: Glycyrrhiza resources were collected from five nations. Leaf margin has been identified as a species-specific characteristic that distinguishes G. uralensis and G. glabra. Glycyrrhiza resources were observed in flowers and seeds for 2 years. Leaf abscission began to fall from July and lasted until November according to the characteristics of the resources. As the number of cultivation years increased, root length, rhizome length, and rhizome number were not significantly related, however, root diameter, root weight and rhizome weight were significantly related. The skin root color became dark after a year. Yield (dry weight of underground part) increased mostly from the first to second year, whereas the yield changed depending on resource characteristics in three years. The yield was positively correlated with dry rhizome weight, plant height, stem diameter, and root diameter. Cluster analysis indicated that, they were classified into three clusters. Among them, the resources in group Ⅲ were confirmed to be of high quantity and quality.BRConclusions: GLY13-05, GLY14-02, and GLY14-06 of Glycyrrhiza resources were evaluated as having excellent growth and yield characteristics. Moreover, they can be cultivated in domestic environments.