Salicylate and biomass yield, and leaf phenolics of dark-leaved willow ( Salix myrsinifolia Salisb.) clones under different cultivation methods after the second cultivation cycle

Abstract

Willow based herbal products containing salicin and its derivatives can be used to alleviate aches and fevers. To guarantee the high quality of the willow drugs and moderate low cultivation and transportation costs, the willows with high salicylate concentrations are recommended for herbal production. Dark-leaved willow ( Salix myrsinifolia Salisb.) with its high salicylate content is a promising source of herbal drugs. In the present study, seven dark-leaved willow clones were cultivated under short-rotation system with a two-year cultivation cycle. The yields of salicylates and biomass, and the concentrations of foliar phenolics were determined after the second cultivation cycle. Willow clones were treated by different cultivation methods, i.e. combinations of mulching (black polythene vs. cutter chip) and fertilisation (0, 25, 150 kg ha −1, N), with the objective of evaluating the most productive clone and cultivation method for herbal willow production. Furthermore, we compared our results to those obtained after the first cultivation cycle. Results showed that the yields of salicylates and biomass, and the concentrations of all foliar phenolic metabolites varied significantly amongst the clones. Biomass yields and salicylate yield were increased by polythene mulching, but the level of response varied between clones. Fertilisation (only the highest rate) caused an increase in yields, but the effect of fertilisation was smaller than that of mulching. Salicylate yield of most clones was higher than that had been during the previous rotation. Phenolic analyses showed that the concentrations of chlorogenic acid, total p-OH-cinnamic acids and soluble condensed tannins were higher in the willows grown in polythene mulch plots than in willows grown on cutter chip mulched plots. Furthermore, the concentrations of diglucoside of SaOH, salicin, disalicortin 1, disalicortin 2, chlorogenic acid, total chlorogenic acids and total flavonoids were higher in fertilized than in unfertilized willows. Salicortin, which was the most abundant salicylate, and total salicylates were not affected by fertilisation and mulching. The effects of fertilisation and mulching on several phenolics were clone-dependent. In conclusion, after two cultivation cycles, the cultivation methods were not effective in increasing the foliar total salicylate concentration, but rather increased the salicylate yield by enhancing the biomass of the synthesising tissues. Since biomass production was increased by the second cultivation cycle, the cultivation of herbal willows under a two-year cycle is recommended. The highly variable responses of the clones to treatments indicate that profitable willow cultivation for herbal industry is based on the right clone selection.