Salvia castanea Hairy Roots are More Tolerant to Phosphate Deficiency than Salvia miltiorrhiza Hairy Roots Based on the Secondary Metabolism and Antioxidant Defenses

Salvia miltiorrhiza is a well-known traditional Chinese herb which is used to treat heart disease. Salvia castanea is a substitute product for S. miltiorrhiza in the medicinal field. Previous study has shown that phosphate (Pi) deficiency could promote the accumulation of secondary metabolism in herbs, and it has also developed a strategy for saving Pi resources and increasing the yield of active substances in herbs. In the present study, the hairy roots of S. miltiorrhiza and S. castanea were used to identify the Pi deficiency response mechanisms of these two Salvia species. The results showed that Pi deficiency increased the accumulation of specifically secondary metabolites, such as phenolic acids and tanshinones, which were caused by promoting the expression levels of key enzyme genes. In addition, Pi deficiency promoted the antioxidant activity in these two Salvia species. The data demonstrated that Pi deficiency increased the quality of the medicinal material in the plant. The hairy roots of S. castanea were more adaptive to Pi deficiency than those of S. miltiorrhiza in terms of biomass, secondary metabolism, and antioxidant activity. The results of this study provide insights into breeding herbs that are better adapted to Pi deficiency, which could increase the yield of active ingredients in herbs and save Pi resources.