Detection and identification of the elm yellows group phytoplasma associated with Puna chicory flat stem in China.

In 2010 and 2011, the Puna chicory flat stem (PCFS) symptom was observed in an experimental field around Yangling, Shaanxi Province, China. Pleomorphic phytoplasma-like bodies were observed in the phloem sieve tube elements of symptomatic plants under transmission electron microscope (TEM). The presence of phytoplasma was further confirmed by a nested polymerase chain reaction (PCR), which amplified a 1.2 kb fragment using universal primer pairs P1/P6 followed by further amplification using primer pairs R16F2n/R16R2. The 1.1 kb 16S rRNA gene fragments were obtained by nested PCR with primer pairs P1/P6 followed by 16SrV group-specific primer pairs R16(V)F1/R16(V)R1 and indicated that the PCFS phytoplasma was closely related to the elm yellows (EY) group (16SrV). Phylogenetic analysis and restriction fragment length polymorphism (RFLP) analysis demonstrated that the PCFS phytoplasma belongs to subgroup 16SrV-B. This is the first report of Puna chicory disease associated with a subgroup 16SrV-B of phytoplasma in China. [ABSTRACT FROM AUTHOR]