Different phytoplasmas infecting purple coneflower in Italy

Echinacea purpurea (L.) Moench. (Asteraceae family), purple coneflower, is an ornamental species widely cultivated as medicinal plant having different biological activities, in particular nonspecific immunostimolatory and wound healing properties. Flower symptoms, including stunting, virescence, phyllody and abnormal flower bud proliferation, have been described in USA, Canada and Europe. Different phytoplasmas, mainly belonging to diverse subgroups (16SrI-A, 16SrI-B and 16SrI-C) in the ‘Candidatus Phytoplasma asteris’ group, were associated with these symptoms. During surveys carried out in May/June 2008 symptoms possibly related to phytoplasma presence were observed in two areas of Emilia-Romagna region. Almost 50% of purple coneflowers obtained by seeds and grown in the open field at the Herb Garden of Casola Valsenio (Ravenna province), showed virescence and stunting of the plants; while at the herb garden of the Bologna Agriculture Faculty severe symptoms including phyllody, proliferation of axillary shots and flower abnormalities were observed in one plant out of ten. Based on RFLP analyses of the 16Sr DNA PCR products phytoplasmas belonging to subgroups 16SrI-B and 16SrIX-C were identified in Casola Valsenio samples, but not in mixed infection. In samples from Bologna only 16SrIX-C phytoplasma were identified. This is the first report of these phytoplasmas in purple coneflower; the 16SrIX-C phytoplasmas were also identified in asymptomatic samples of Taraxacum and Amaranthus collected in vineyards in Modena province, while in malformed Amaranthus samples collected near to infected purple coneflower plants 16SrIX phytoplasmas detected differed from 16SrIX-C for a TaqI restriction profile. Further phytoplasma characterization to verify epidemiological aspects is in progress.