Thidiazuron induced efficient in vitro organogenesis and regeneration of Scutellaria bornmuelleri: an important medicinal plant

Abstract

Scutellaria, a genus of the Lamiaceae family, comprises over 350 species of annual and perennial herbs distributed in the world (Brickell 1996). There are 20 species and two hybrids of this genus in Iran (Ghahreman and Attar 1999; Emami and Aghazari 2011). Of the Scutellaria species, S. baicalensis Georgi is used in traditional Chinese medicine and Japanese Pharmacopeia for over 2000 yr to treat bronchitis, hepatitis, diarrhea, tumors (Zobayed et al. 2004), hypertension, infectious disease, inflammatory, and allergic diseases (Shang et al. 2010). The presence of flavones, such as baicalin, wogonoside, wogonin, baicalein, and luteolin, is responsible for pharmacological activities of S. baicalensis (Shang et al. 2010). Scutellaria bornmuelleri Hausskn. ex Bornm. subsp. mianensis Rech.f, an annual herb from Scutellaria genus, is an endemic plant distributed in the East Azerbaijan province of Iran (Fig. 1). All parts of plant such as herbs, leaves, fruits, roots, and seeds are popularly used in preparation of various traditional medicines to treat constipation, wound healing, and stress (Zargari 1997). In recent years, the distribution of S. bornmuelleri is endangered because of severe grazing and collection by people to be used in folk medicine, and so, this species is at risk of extinction. Although there are numerous reports on in vitro tissue culture of Scutellaria genus (Cole et al. 2008; Wilczyńska-Barska et al. 2012; Grzegorczyk-Karolak et al. 2016), there is no report on S. bornmuelleri. Thidiazuron, a synthetic cytokinin, induces many responses such as stimulating the induction of shoot regeneration and somatic embryogenesis in some plant species (Zhang and Li 1995; Akasaka et al. 2000; Shan et al. 2000). In some species, it was proved that TDZ activity is about 30 times higher than zeatin activity (Susan et al. 1997). However, the precise mechanism of TDZ action is not completely clear. The purpose of this study was to investigate the effect of TDZ on direct and indirect adventitious shoot regeneration from leaf, stem, and petiole explants.