Ming aralia (Polyscias fruticosa), a new host of phytoplasma subgroup 16SrVII-B 'Candidatus Phytoplasma fraxini'- related strains, in Brazil

Authors: PEREIRA, T - Universidad De Sao Paulo; BANZATO, T - Universidad De Sao Paulo; BEDENDO, I - Universidad De Sao Paulo; Dally, Ellen; Davis, Robert

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/27/2015
Publication Date: 3/1/2016
Citation: Pereira, T.B., Banzato, T.C., Bedendo, I.P., Dally, E.L., Davis, R.E. 2016. Ming aralia (Polyscias fruticosa), a new host of phytoplasma subgroup 16SrVII-B 'Candidatus Phytoplasma fraxini'- related strains, in Brazil. Plant Disease. 100:645.

Interpretive Summary: Phytoplasmas are minute, specialized bacteria causing plant diseases that result in economic losses worldwide. They are spread by insects that feed in the food conducting tissues in veins, where phytoplasmas live and induce disease symptoms including development of abnormally small leaves. Phytoplasmas can be introduced into new geographic regions by the transportation and cultivation of vegetatively propagated, infected plant parts that serve as a source of phytoplasma for spread to crops in the new region. To reduce the spread of phytoplasmas, it is important to know whether or not a given plant is or can be infected by a phytoplasma. In this work, we investigated a disease of ming aralia (Polyscias fruticosa) plants. We analyzed the DNA of the diseased plant and found that it contained a gene that was derived from a phytoplasma that was infecting the plant. Further analysis of the gene revealed that the phytoplasma was related to, but different from, a phytoplasma that had previously been found to cause diseases in ash trees in the U.S. and Canada, and diseases in a weed and Madagascar periwinkle plants. ). Our new information expands knowledge of plant diseases that can be caused by phytoplasmas related to the North American ash disease phytoplasma, and it provides a way using molecular markers to recognize the phytoplasma and prevent its introduction into U.S. agriculture.

Technical Abstract: Ming aralia (Polyscias fruticosa) plants affected by a disease (ming aralia little leaf (MaLL)) in Brazil were observed to exhibit symptoms of yellowing and abnormally small leaves, indicative of the presence of a phytoplasma in the diseased plants. Amplification of DNA in PCRs, containing template from the symptomatic plant and phytoplasma-universal oligonucleotide primers, generated 1.6 kb genomic fragments containing a phytoplasmal 16S rRNA gene, further indicating infection by a phytoplasma. The PCR products were purified and sequenced using 10 primers to achieve 4X to 5X coverage per base position. A BLASTn search, using the amplified DNA sequence as query, yielded best hit with Erigeron witches'-broom phytoplasma (EriWB), a member of ash yellows phytoplasma group (16SrVII). Phytoplasma group 16SrVII was originally reported in United States and Canada infecting Fraxinus spp. and Syringa sp. In silico RFLP patterns of the amplified 16S rRNA gene, obtained by using the iPhyClassifier online tool, were indistinguishable from those characteristic of subgroup 16SrVII-B. The phytoplasma identified in the diseased ming aralia plant was termed MaLL-Br01. Nucleotide sequence alignments revealed that MaLL-Br01 phytoplasma shared 100% 16S rRNA gene sequence identity with the EriWB phytoplasma, reference strain of subgroup 16SrVII-B. The MaLL-Br01 phytoplasma 16S rRNA gene sequence was deposited in the GenBank database (Accession no. KP828428). In Brazil, phytoplasmas belonging to subgroup 16SrVII-B have been reported in diseased plants of Erigeron sp., and Cantharanthus roseus in the state of São Paulo (Barros et al. 2002). Our findings expand knowledge of the natural host range of subgroup in 16SrVII-B strains and reveal P. fruticosa as a new host of this phytoplasma subgroup lineage.