First Report of Purple Coneflower Phyllody Associated with a 16SrI-B Phytoplasma in Maryland.

Abstract

Purple coneflower (Echinacea purpurea (L.) Moench) is a flowering perennial plant native to North America and is widely grown as an ornamental flower. It is also grown commercially to make herbal teas and extracts purported to help strengthen the immune system. Propagation is by seed or root cuttings. Aster yellows phytoplasmas (strains belonging to group 16SrI) have been reported to be associated with purple coneflower exhibiting virescence and phyllody symptoms in the northern United States and Canada. A subgroup 16SrI-A phytoplasma was identified to be associated with symptomatic purple coneflower in Wisconsin (2). During the summers of 1994 and 2007, purple coneflower plants in Maryland sporadically exhibited symptoms resembling those caused by phytoplasma infection. Symptoms included stunting, virescence, phyllody, and abnormal flower bud proliferation from the cone. Samples from four symptomatic and two asymptomatic purple coneflower plants were collected. Total nucleic acid was extracted from leaf tissue. To assess the etiology of the disease, nested PCR with universal phytoplasma primer pair P1/P7 followed by R16F2n/R16R2 was employed for the detection of phytoplasmas (1). An amplicon of approximately 1.2 kb was amplified from all four symptomatic purple coneflower plants but not from the two asymptomatic plants. Restriction fragment length polymorphism (RFLP) patterns of 16S rDNA digested singly with restriction enzymes AluI, KpnI, HpaI, MseI, HhaI, and RsaI indicated that affected purple coneflower plants were infected by a phytoplasma belonging to aster yellows group 16SrI ('Candidatus Phytoplasma asteris'-related strains), subgroup 16SrI-B (1). Nucleotide sequence analysis of cloned 16S rDNA (GenBank Accession Nos. EU333394 and EU333395) confirmed the results from RFLP analyses. To our knowledge, this is the first report of a 16SrI-B phytoplasma infecting an Echinacea sp. in Maryland.