DISEASE NOTESOpen Access icon OPENOpen Access license

First Report of ‘Candidatus Phytoplasma asteris’ Subgroup 16SrI-AE Associated with Winter Jasmine Witches’ Broom in Shandong, China

    Affiliations
    Authors and Affiliations
    • X.-J. Xu
    • W.-C. Chang , Shandong Key Laboratory of Agricultural Microbiology, Department of Plant Pathology, College of Plant Protection, Shandong Agricultural University, Tai’an 271018, China
    • R. Gao , Shandong Key Laboratory of Agricultural Microbiology, Department of Plant Pathology, College of Plant Protection, Shandong Agricultural University, Tai’an 271018, China, and Shandong Academy of Agricultural Sciences, Tai’an, Shandong 271000, China
    • D.-F. Wei
    • X.-Z. Chen
    • X.-D. Li , Shandong Key Laboratory of Agricultural Microbiology, Department of Plant Pathology, College of Plant Protection, Shandong Agricultural University, Tai’an 271018, China.

      Winter jasmine (Jasminum nudiflorum) is an ornamental plant widely cultivated around the world. Symptoms of small leaves, witches’ broom, and shortened branches were observed in mature winter jasmine plants in Tai’an, Shandong Province, China, in August 2005. These symptoms were frequent with an incidence of 5 to 8% in a garden of 20 ha. Spheroidal, ovoid, and irregular tubular wall-less prokaryotes were observed in the phloem sieve tubes of symptomatic tissues. To further confirm the association between winter jasmine witches’ broom and phytoplasma infection, total DNA was extracted from 1 g of phloem tissue of four symptomatic branches from different plants and two healthy branches from different asymptomatic winter jasmine plants. The 16S rRNA-encoding gene was amplified with universal phytoplasmal primer pairs R16mF2/R16mR1 and R16F2n/R16R2 via nested polymerase chain reaction (Gundersen et al. 1996; Lee et al. 1998), producing a specific fragment of 1,243 bp (accession no. JX094040) from all the symptomatic but not from healthy-looking winter jasmine plants. A 1,215-bp fragment specific for phytoplasmal ribosomal protein (rp) gene (accession no. JX094041) was obtained from all the symptomatic but not from the asymptomatic samples when amplified with primer pair rpF1 and rpR1 (Lee et al. 2004; Lim and Sears 1992). All these results confirmed the association of phytoplasma infection with winter jasmine witches’ broom symptom. The associated phytoplasma was designated as Jasminum nudiflorum witches’ broom (JNWB) phytoplasma. The 16S rRNA of JNWB phytoplasma shared identities of 99.25, 99.17, and 98.6% with those of paulownia witches’ broom phytoplasma (AY265206), Maryland aster yellows phytoplasma (M30790), and broadbean phytoplasma (DQ286953), the representative strains of ‘Candidatus Phytoplasma asteris’ 16SrI-D, 16SrI-B, and 16SrI-AE (Wei et al. 2008). In the phylogenetic tree constructed with 16S rRNA, JNWB phytoplasma clustered together with those of 16SrI-D, 16SrI-B, and 16SrI-AE subgroups. However, the results of iPhyClassifier showed that the 16S rRNA gene patterns of the JNWB phytoplasma were identical to and had a similarity coefficient (F) of 1.0 with that of 16SrI-AE (DQ286953) (Wei et al. 2008). We did not directly address the possibility of 16S rRNA-encoding gene heterogeneity, although the two clones that were examined had identical sequences. The rp gene of JNWB phytoplasma shared the highest identity of 99.9% with those of rp I-D strains (HM146079 and AF453327). In the phylogenetic tree constructed with rp genes, JNWB phytoplasma formed a close branch with those associated with paulownia witches’ broom. Taken together, our results indicate that JNWB phytoplasma is a strain of 16SrI-AE. To our knowledge, this is the first report that JNWB in China is associated with a phytoplasma and that the phytoplasma is ‘Ca. P. asteris’ 16Sr I-AE. Our results will inform strategies for the control of winter jasmine witches’ broom disease.

      References:

      Funding: Funding was provided by "Taishan Scholar" Construction Project (ts201712023).