Submitted to: Plant Disease
Publication Type: Research Notes
Publication Acceptance Date: 1/30/2008
Publication Date: 4/1/2008
Citation: Lee, I., Bottner, K.D., Dally, E.L., Davis, R.E. 2008. First report of purple coneflower phyllody associated with a 16SrI-B phytoplasma in Maryland. Plant Disease. 92:654.
Interpretive Summary: Phytoplasma are very small bacteria that lack a cell wall and that cause several hundred economically important diseases in plants, including fiber, fruit, vegetable and ornamental crops, and forest trees. Purple coneflower (Echinacea purpurea (L.) Moench) is a flowering perennial plant native to North America and widely grown as an ornamental flower. It is also grown commercially to make herbal teas and extracts purported to help strengthen the immune system. During the summers of 1994 and 2007, purple coneflower plants in Maryland sporadically exhibited symptoms resembling those caused by phytoplasma infection; diseased plants develop green discoloration and abnormal leaf-like structure of flowers (termed phyllody). Phytoplasma strains in the aster yellows subgroup (16SrI-A) have been reported to cause diseases in purple coneflower in Canada and the northern US, but phytoplasmal diseases have not previously been reported in purple coneflower in Maryland. In the present study, we used molecular procedures and found that diseased purple coneflower plants in Maryland were infected by a different aster yellows phytoplasma strain belonging to a subgroup16SrI-B. This information will aid implementation of quarantine regulations and will help extension workers and plant diagnosticians to combat the disease.
Technical Abstract: Purple coneflower (Echinacea purpurea (L.) Moench) is a flowering perennial plant native to North America and widely grown as an ornamental flower. During the summers of 1994 and 2007, purple coneflower plants in Maryland sporadically exhibited symptoms resembling those caused by phytoplasma infection. 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, using universal phytoplasma primer pair P1/P7 followed by R16F2n/R16R2, was employed for the detection of phytoplasmas. An amplicon of about 1.2 kb was amplified from all four symptomatic purple coneflower plants but not from the two asymptomatic plants. Restriction fragment length polymorphism 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’ and related strains), subgroup 16SrI-B. Nucleotide sequence analysis of cloned 16S rDNA confirmed the results from RFLP analyses.