Archivio Journal of Plant Pathology

Abstract:

Celosia argentea L. (Amaranthaceae), is an annual herb and ornamental plant frequently seen in China. In 2015, symptoms of witches’-broom and phyllody were observed on C. argentea in Haikou, Hainan province, China. Three symptomatic plants and two asymptomatic ones were collected for phytoplasma detection and classification (Dickinson and Hodgetts, 2013). Total DNAs were extracted, and phytoplasma diagnosis was performed by nested PCR using primer pairs P1/P7 and R16F2n/R16R2n. Fragments about 1.8 (P1/P7) and 1.2 kb (R16F2n/R16R2n) were only detected in all symptomatic plant samples, which confirmed phytoplasma infection. For phytoplasma classification, 16S rRNA gene and rp (ribosomal proteins) gene were amplified by high-fidelity DNA polymerase with primers P1/P7 and rp(II)F1/rp(II)R1, and three clones of each amplicon from each sample were sequenced. The consistent sequences were deposited in GenBank with accession number KX426374 (16S rRNA) and KX426375 (rp). Partial 16S rRNA gene sequences (between R16F2n and R16R2n) were used for C. argentea phytoplasma identification at group and subgroup levels. Phylogenetic tree analysis, performed by MEGA 5.0 using neighbor-joining method, showed C. argentea phytoplasma was grouped with 16SrII group phytoplasmas. Virtual RFLP analysis, carried out by iPhyClassifier, showed that RFLP profile from C. argentea phytoplasma was consistent with that of Peanut witches’-broom phytoplasma, a 16SrII-A subgroup phytoplasma. To our knowledge, this is the first report about a 16SrII-A subgroup phytoplasma associated with phytoplasma disease on C. argentea in China, although 16SrII phytoplasmas were detected in the same host showing little leaf and witches’-broom on Guadalcanal in the Solomon islands (Davies and Tsatsia, 2009).