Lilac ( Syringa sp.) Hosts a New ‘ Candidatus Phytoplasma pruni’-related Strain in Utah: Ribosomal RNA and secY Genes Distinguish the Phytoplasma from Previously Described Lineages

A decline in lilac (Syringa sp.) has been observed in Utah for over 25 years. Symptoms initially included leaf chlorosis, mosaic, and rolling, and diseased plants eventually died over a period of 2 to 3 years. Polymerase chain reaction assays (PCRs) for amplification of ribosomal (r) RNA gene sequences (rDNA) (primers, P1/16S-SR) and secY genomic regions were used to assess possible association of a phytoplasma with the disease, lilac decline (LlcDec). DNA for use as PCR template was separately extracted from excised veins of symptomatic leaves collected from two symptomatic plants. Amplicons of rDNA were of predicted sizes, indicating possible phytoplasmal infection in both plants; nucleotide sequencing confirmed that the amplicons were derived from a phytoplasma. The rDNA and secY sequences, respectively, were mutually identical for the phytoplasma strains detected in the two plants. Phytoplasma asteris'-related strain, the symptoms associated with infection by the 'Ca. Phytoplasma pruni'-related strain reported here differ from those associated with infection of lilac by the other phytoplasmas.