Effect of Rhizophagus irregularis arbuscular-mycorrhizal fungus on bioactive compounds and growth parameters of two-years-old Echinacea purpurea plants

Echinacea purpurea is a perennial plant used mostly for its immune-stimulating aerial parts. Even though Echinacea has been a commercial success, the cultivation industry continues to face challenges because of the long duration till harvesting, seed dormancy, climatic conditions, soil type, and pest management. The study aimed to understand the long-term effects of arbuscular mycorrhizal fungus (AMF) on growth parameters and bioactive principle content by cultivating E. purpurea plants with Rhizophagus irregularis on sterile peat and various soil types, in pots and open-field conditions. R. irregularis significantly increased the content of caftaric acid (sterile peat, 1.40-fold), chlorogenic acid (gleyic calcaric Fluvisol, 7.62-fold; stagnic Luvisol, 23.18-fold; sterile peat, 8.77-fold; and open-field stagnic Luvisol, 5.86-fold), caffeic acid (gleyic calcaric Fluvisol, 15.46-fold; calcaric Regosol, 39.63-fold; stagnic Luvisol, 19.68-fold; sterile peat, 110.91-fold; and open-field stagnic Luvisol, 85.80-fold), cynarin (sterile peat, 3.14-fold), and echinacoside (sterile peat, 12.74-fold and open-field stagnic Luvisol 14.44-fold). Furthermore, chlorogenic acid (on calcaric Regosol) and echinacoside (on calcaric Regosol and stagnic Luvisol) were only present in treated plants. The AMF treatment enhanced germacrene D levels (21.33-fold) in herba in potted plants cultivated on gleyic calcaric Fluvisol. This is the first study that shows the long-term effects of plant-AMF interactions in E. purpurea. Cultivation of E. purpurea with R. irregularis as a perennial crop proved to be economically profitable due to the higher biomass and significantly increased phenolic content in the second year of the plant. Experiments with other AMF species and combinations with plant growth-promoting rhizobacteria should be explored in future studies.