Influence of Virus Diseases on the Yield of the Medicinal Plant Echinacea purpurea

Symptoms of virus diseases on the leaves of the medicinal plant species Echinacea purpurea (L.) Moench. – purple coneflower were observed in the trial fields of the Institute of Rose, Essential and Medicinal Cultures (IREMC) near Kazanlak and private gardens in Kazanlak, Bulgaria. Virus diseases, caused by the following viruses were established on E. purpurea: Alfalfa mosaic virus (AMV), Cucumber mosaic virus (CMV), Tobacco mosaic virus (TMV), Tomato spotted wilt virus (TSWV) and Potato virus Y (PVY). These viral pathogens existed in Echinacea plants in individual or most commonly in mixed infections. The symptoms caused by viral pathogens were spotting (chlorotic spots of different shape and size) on the leaves, sometimes typical mosaic, reduction in leaf size and flower head diameter and especially decrease in the height of the stems, called dwarfing. The results of the study have shown, that the most widely spread were СМV, АМV, ТМV - over 45 % and TSWV – nearly 30 %. Clear differences were detected in the yields of roots, seeds and leaves between Group I of symptomless Echinacea plants (practically healthy without symptoms or damage) and the spotted Echinacea plants (Group II – of spotted and dead plants and Group III - of spotted, but vital plants, in which the viruses were established. The spotted Echinacea plants were shorter (dwarfed) in comparison with the symptomless plants with fewer leaves and flower heads. The yield of the seeds, leaves and roots of the spotted plants was twice or several times lower in comparison with the symptomless plants.