Abstract
The root of Chinese sage (Salvia miltiorrhiza Bunge) was regarded as top-grade Chinese medicine two thousand years ago, according to Shen Nong Materia Medica. The aim of this study is to develop an easy and reliable means for obtaining tetraploids (4x plants) via thidiazuron-induced direct organogenesis in the presence of colchicine. The resulting 4x plants showed significantly enhanced agronomic traits, including the size of stomata, leaflet, pollen, and seed as well as shoot length, root diameter, number of leaves, and fresh weight of plant. In addition, an obvious reduction of length to width ratio was found in the 4x plants, including stomata, leaflets, pollens, seeds, and roots. The 4x ploidy state of the plants was stable as was proved by evaluation of selection indicators as well as consistent ploidy level at 10th generation plantlets and also on 4x seedlings obtained via self-pollination. The major bioactive compounds, salvianolic acid B, tanshinone I, tanshinone IIA, dihydrotanshinone I and cryptotanshinone, as well as total tanshinones were determined by high performance liquid chromatography (HPLC). The concentrations of dihydrotanshinone I and total tanshinones in the root extract of the 4x plants were significantly higher when compared with the 2x plants. This present study developed a simple and efficient system for inducing and subculture of tetrapolids which have stable ploidy level, enhanced growth characteristics as well as the content of dihydrotanshinone I in the root of S. miltiorrhiza.