INTERACTION BETWEEN ENDOPHYTIC BACTERIAL COMMUNITIES ISOLATED FROM THE STEM/LEAF AND ROOT COMPARTMENTS OF THE MEDICINAL PLANTS ECHINACEA PURPUREA AND ECHINACEA ANGUSTIFOLIA.

The present work aimed to understand if distinct bacterial communities could account for the differences in the medicinal properties of two Echinacea plant species by affecting their physiology and metabolism. Axenic E. purpurea and E. angustifolia plants were infected with E. purpurea endophytes and examined for the presence of bacteria and for different physiological parameters. Dual cultures experiments between Echinacea cell cultures and different bacteria were established to test the influence on both plant and bacterial cells growth. Results showed that endophytic strains tended to recolonize the host plant native niche, endophytes from stem/leaves increasing the number of leaves, or the plant weight if coming from roots. In vitro morphogenetic behaviour indicated that the two Echinacea species had a different content of endogenous plant hormones. E. purpurea was able to regenerate new shoots in culture media enriched with high content of cytokinins while E. angustifolia produced only clusters of undifferentiated cells (callus). In vitro colonization of endophytes was divergent according to their native in vivo compartment. These results suggest that different composition in plant primary metabolism in the two Echinacea species could affect the plant-bacteria interaction modulating the production of plant metabolites, key compounds for colonization strictly related to the Echinacea therapeutic properties.