The present study aimed to develop a protocol for root induction and evaluate the effects of salicylic acid (SA) (0, 80 and 160 mg/l) and yeast extract (YE) (0, 0.75 and 1.5 g/l) on chlorogenic acid, caftaric acid, cichoric acid, cynarin and echinacoside production in Echinacea purpurea adventitious roots. Also, the effect of NH4NO3 (0, 0.25, 0.75, 1.0 X) concentration in MS medium supplemented with indole-3-acetic acid (IAA) (1 and 3 mg/l) on root induction was investigated. The results showed that adventitious root induction in coneflower was significantly influenced by NH4NO3 and IAA concentrations (p≤0.01). The highest percentage of root induction (100%) and average number of roots formed on each explant (14.3 roots) was observed in 1 mg/l IAA×1/4NH4NO3 MS culture medium treatment. The main effect of SA and YE and their interaction effects with exposure time on the measured traits (except for echinacoside) was significant (p≤0.01). The result showed that application of 1.5 g/l YE and 160 mg/l SA when harvested 96 hour post-elicitation are the most effective treatments to elicit caffeic acid derivatives (CADs) content. The highest chlorogenic acid, cichoric acid, caftaric acid, and cynarin production was obtained in 160 mg/l SA at 96 hours post-elicitation that was 2.13, 1.83, 2.39 and 2.97-fold higher compared to control respectively. The heatmap diagram showed that the CADs content in SA and YE treatments was clearly separated from each other and control treatment.
