Archivio Journal of Plant Pathology

Abstract:

Melochia corchorifolia L. is a herb and weed commonly found in China. In August 2015, three M. corchorifolia plants displaying symptoms of phytoplasma infection such as witches’-broom, virescence and phyllody were found in two wastelands in Haikou, Hainan province, China. All symptomatic and three asymptomatic plants were collected for phytoplasma detection and classification (Dickinson and Hodgetts, 2013). Phytoplasma diagnosis was performed by nested PCR using phytoplasma universal primers P1/P7 and R16F2n/R16R2. Fragments ca. 1.8 (P1/P7) and 1.2 kb (R16F2n/R16R2) in size were only observed in symptomatic samples. For phytoplasma classification, gene fragments were amplified using R16F2n/R16R2 primers for 16S rRNA, rp(I)F1A/rp(I)R1A for rp, and fTufu/rTufu (Schneider et al., 1997) for tuf genes, respectively; three clones of each were sequenced. The consensus sequences were submitted to GenBank with the accession numbers KX150461 (16Sr RNA), KX158198 (rp) and KX158199 (tuf). A phylogenetic tree based on the partial 16Sr RNA gene sequences (1246 nt) from M. corchorifolia phytoplasma (Mcp) and other phytoplasma group representatives was built by MEGA 5.0 using neighbor-joining method. It showed that Mcp clustered with 'Candidatus Phytoplasma asteris' (16SrI group) phytoplasmas. Furthermore, virtual RFLP analyses were performed by iPhyClassifier and Vector NTI. 16Sr RNA, rp and tuf gene RFLP profiles of Mcp were consistent with the RFLP profiles of 16SrI-B, rpI-B and tuf-B subgroup phytoplasmas. To our knowledge, this is the first report on M. corchorifolia phytoplasma worldwide.