'Candidatus Phytoplasma dypsidis', a novel taxon associated with a lethal wilt disease of palms in Australia

Abstract

A phytoplasma was initially detected in Dypsis poivriana by nested and real-time PCR from the botanical gardens in Cairns, Queensland, Australia in 2017. Further surveys in the Cairns region identified phytoplasma infections in eight additional dying ornamental palm species (Euterpe precatoria, Cocos nucifera, Verschaffeltia splendida, Brassiophoenix drymophloeodes, Burretiokentia hapala, Cyrtostachys renda, Reinhardtia gracilis, Carpoxylon macrospermum), a Phoenix species, a Euterpe species and two native palms (Archontophoenix alexandrae). Analysis of 16S rRNA gene sequences showed that this phytoplasma is distinct as it shared less than 97.5 % similarity with all other ‘Candidatus Phytoplasma’ species. At 96.3 % similarity, the most closely related formally described member of the provisional 'Ca. Phytoplasma' genus was 'Ca. Phytoplasma noviguineense', a novel taxon from the island of New Guinea found in monocotyledonous plants. It was slightly more closely related (96.6–96.8 %) to four palm-infecting strains from the Americas, which belong to strain group 16SrIV and which have not been assigned to a formal 'Candidatus Phytoplasma’ species taxon. Phylogenetic analysis of the 16S rRNA gene and ribosomal protein genes of the phytoplasma isolate from a dying coconut palm revealed that the phytoplasma represented a distinct lineage within the phytoplasma clade. As the nucleotide identity with other phytoplasmas is less than 97.5 % and the phylogenetic analyses show that it is distinct, a novel taxon 'Candidatus Phytoplasma dypsidis' is proposed for the phytoplasma found in Australia. Strain RID7692 (GenBank accession no. MT536195) is the reference strain. The impact and preliminary aspects of the epidemiology of the disease outbreak associated with this novel taxon are described.

Revision of the ‘Candidatus Phytoplasma’ species description guidelines

“…P. castaneae’ strain CnWB [22] (GenBank accession number AB054986) starts at nucleotide 10, for ‘ Ca . P. dypsidis’ strain RID7941 [23] (GenBank accession number MT293886) at nucleotide 25; for ‘Ca . P. caricae' strain PAY [24] (GenBank accession number AY725234) and ‘Ca .…”

“…It was recently described in Australia [23] from dying ornamental palms belonging to several species. Six strains with coverage >95 % show sequence identities between 99.83% and 99.88 % compared to the reference strain RID7692 (GenBank accession number MT536195).…”

Plant Virus and Virus-like Disease Threats to Australia’s North Targeted by the Northern Australia Quarantine Strategy

“…However, more variation exists within the group of closely related phytoplasmas causing wilt symptoms in cooking banana plants. In published phylogenetic analyses [ 78 , 79 ], it can be seen that BWAPs from the Autonomous Region of Bougainville and the Solomon Islands separate out from members of ‘ Ca. P. noviguineense’ from PNG’s northwest.…”

Silencing of ATP Synthase β Impairs Egg Development in the Leafhopper Scaphoideus titanus, Vector of the Phytoplasma Associated with Grapevine Flavescence Dorée

“…Scaphoideus titanus is the primary vector of Flavescence dorée phytoplasma (FDp), a quarantine pest of grapevine in the EU with a severe impact on European viticulture [ 4 , 5 ]. Phytoplasmas are a group of cell wall-less bacteria with small genome sizes (530–2220 kb) belonging to the class Mollicutes and to date, mainly based on 16Sr genetic data, 47 ‘ Candidatus Phytoplasma species’ have been described [ 6 , 7 , 8 , 9 ]. Phytoplasmas are obligate bacterial plant pathogens, infecting phloem of the host plants as well as the body of insect vectors.…”