Thidiazuron and LED Lighting Enhance Taxifolin and Rutin Production in Rhododendron mucronulatum Turcz. Microshoot Culture

Rhododendron mucronulatum Turcz., distributed throughout the northern region of East Asia has been considered to be an alternative natural source of taxifolin (dihydroquercetin) and rutin. The present study was conducted based on a biotechnological approach to develop an environment friendly and efficient system to produce taxifolin and rutin in R. mucronulatum microshoots, using different thidiazuron (TDZ) treatments (0.1; 0.5; 2.5 µM) in combination with various types of lighting including fluorescent (FL) and light-emitting diode (LED) (R/B− 80% red + 20% blue; 5LED-20% red + 20% blue + 20% green + 20% yellow + 20% white). The highest number of shoots per explant was obtained under 0.5 µM TDZ combined with 5LED in comparison with FL lighting. Among shoot clusters obtained under different lighting types and TDZ concentrations, a considerable increase in fresh and dry weight was observed in ones cultivated on medium, supplemented with 2.5 µM TDZ under FL and 0.5 µM TDZ at R/B or 5LED. The content of total chlorophylls in R. mucronulatum microshoots increased on TDZ-free medium under FL lighting, whereas, the TDZ treatment decreased chlorophylls concentration at FL and 5LED. The use of 0.1 µM TDZ at 5LED decreased the ratio of chlorophylls a + b to carotenoids and led to the highest accumulation of taxifolin and rutin, quercetin, hyperoside, and avicularin. Thus, it has been demonstrated that the application of combined action of LED and TDZ has great potential in terms of propagation efficiency, biomass accumulation, and taxifolin and rutin production in R. mucronulatum microshoots.