There is an increasing worldwide demand for herbal plants, particularly in advanced nations. The majority of herbs are used to make teas, dishes, and functional foods with the intention of enhancing health. Asia is an area with a large potential for natural herbal resources due to its geographic and meteorological conditions, according to numerous research on the distribution of oriental medicinal plants. One of these, Huang Qi (Astragalus membranaceus) “Hwang-gi” in Korea, which belongs to the Fabaceae family, is a significant and useful medicinal herb utilized in both traditional therapies and clinical applications (Chen et al. 2020; Fan et al. 2020; Liu et al. 2019; Liu et al. 2021; Wang et al. 2021; Zhang et al. 2020).
The roots of A. membranaceus, also can be translated into “yellow leader”, which refers to the yellow color of roots as well as its status: one of the important tonic medicinal plants in traditional Chinese medicine. In the first book of Chinese herbal medicine, “Shen Nong Ben Cao Jing”, A. membranaceus was documented as a superior herb and classified into the “qi”-tonifying group (Fan et al. 2012). A. membranaceus is endemic to the northern part and the elevated regions of China, including Inner Mongolia, Heilongjiang, Shanxi and Gansu, and also found in Korea and Russia (Wu 2004). There are more than 100 compounds were identified from Huang Qi, involving trace elements, polysaccharides, amino acids, phenolic, flavonoids, and astragalosides (Huang et al. 2018; Liu et al. 2019; Liu and Lv 2020; Xie et al. 2018; Zhao et al. 2012). It has historically been used as an immunomodulator to treat the common cold, fatigue, diarrhea, anorexia, and abnormal uterine bleeding in the traditional Chinese formulae, and it has also been prescribed for the treatment of patients with cardiovascular disease and served as a health food supplement in some Asian populations (Auyeung et al. 2016; Liu et al. 2011). Moreover, isolating and researching natural bioactive compounds from Huang Qi with human benefits has garnered a great deal of interest recently, including antioxidant, antibacterial, anti-inflammatory, anti-cancer, and anti-aging properties (Jin et al. 2014; Nie et al. 2018; Zhang et al. 2020; Zhou et al. 2023). Almost all the bioactive compounds were obtained from the roots. Especially, the 4-7-year-old dried root is the main medicinal portion of this plant, which is collected in spring and autumn. Although the demand for Huang Qi has increased, the availability of its natural resources has diminished annually (Song et al. 2008). Moreover, cultivation in nature was affected strongly by weather and disease. It is not economically feasible to obtain the plant or the cultivated source in nature, and also the secondary metabolites vary with environmental conditions (Ma et al. 2000). To overcome these disadvantages, a promising approach with the aid of tissue cultures is encouraged to tackle such drawbacks by obtaining valuable metabolites along to enhance the yield of the bioactive compound. In this study, we established an in vitro approach for micropropagation of A. membranaceus plant, which created the potential to provide medicinal seedlings source. Otherwise, materials characterized by a high and stable secondary metabolites accumulation rate will contribute importantly to future research and use.
Tissue culture is the technique of growing plant cells, tissues, or organs in artificial media under the sterilized condition with the aim for propagation large copies and biomass of the same samples (Hesami et al. 2021; Long et al. 2022; Loyola-Vargas and Ochoa-Alejo 2018; Murthy et al. 2014; Shin et al. 2020). Numerous studies on tissue culture of Huang Qi plants have been conducted so far, with the majority focusing on adventitious roots or hairy roots culture for secondary compound collection (Ionkova et al. 2010; Sivakumar et al. 2005; Wu et al. 2011). Successful hairy roots culture of A. membranaceu in bioreactor has been investigated for the production of bioactive compounds such as astragalosides, flavonoid and polysaccharides (Gai et al. 2016; Gai et al. 2017; Jiao et al. 2015; Jiao et al. 2016). However, the hairy roots culture of A. membranaceu requires the leaves discs transformation by using Agrobacterium rhizogenes and production of transgenic materials remains debatable. Although there has been successful report of the adventitious roots culture of A. membranaceu in bioreactor to produce secondary compounds (Wu et al. 2011). There are a few studies on the in vitro propagation of this species by tissue culture, better survival rate was observed after soil acclimatization, while in vivo rooting rate (80%) was less efficient compared to in vitro rooting (Han et al. 2014). Although adventitious (Sun et al. 2022; Thwe et al. 2012; Wu et al. 2011) and hairy roots (Park et al. 2015) have been successfully induced for the high yield of secondary metabolites accumulation, however, the previous reports focused on the study of obtaining in vitro plant materials from root explants. There are a few studies on the in vitro propagation of this species by tissue culture, but the coefficient is still low(Han et al. 2014). Moreover, there is no complete propagation procedure for direct and indirect organogenesis of this plant so far. In this study, we have successfully established the micropropagation process of the Huang Qi plant through direct and indirect pathways which not only provides an important contribution to the understanding of organogenesis for micropropagation purposes of this species, but also serves as an important database in material production, which is an abundant and stable source of materials for the acquisition of secondary compounds, for pharmacological applications and clinical experiments. In addition, large-scale micropropagation of this plant for commercial and pharmacological purposes can replace naturally grown conditions.