‘Candidatus Phytoplasma pruni’, a novel taxon associated with X-disease of stone fruits, Prunus spp.: multilocus characterization based on 16S rRNA, secY, and ribosomal protein genes

Abstract

X-disease is one of the most serious diseases known in peach (Prunus persica). Based on RFLP analysis of 16S rRNA gene sequences, peach X-disease phytoplasma strains from eastern and western United States and eastern Canada were classified in 16S rRNA gene RFLP group 16SrIII, subgroup A. Phylogenetic analyses of 16S rRNA gene sequences revealed that the X-disease phytoplasma strains formed a distinct subclade within the phytoplasma clade, supporting the hypothesis that they represented a lineage distinct from those of previously described ‘Candidatus Phytoplasma ’ species. Nucleotide sequence alignments revealed that all studied X-disease phytoplasma strains shared less than 97.5 % 16S rRNA gene sequence similarity with previously described ‘Candidatus Phytoplasma ’ species. Based on unique properties of the DNA, we propose recognition of X-disease phytoplasma strain PX11CT1R as representative of a novel taxon, ‘Candidatus Phytoplasma pruni’. Results from nucleotide and phylogenetic analyses of secY and ribosomal protein (rp) gene sequences provided additional molecular markers of the ‘Ca. Phytoplasma pruni’ lineage. We propose that the term ‘Ca. Phytoplasma pruni’ be applied to phytoplasma strains whose 16S rRNA gene sequences contain the oligonucleotide sequences of unique regions that are designated in the formally published description of the taxon. Such strains include X-disease phytoplasma and - within the tolerance of a single base difference in one unique sequence - peach rosette, peach red suture, and little peach phytoplasmas. Although not employed for taxon delineation in this work, we further propose that secY, rp, and other genetic loci from the reference strain of a taxon, and where possible oligonucleotide sequences of unique regions of those genes that distinguish taxa within a given 16Sr group, be incorporated in emended descriptions and as part of future descriptions of ‘Candidatus Phytoplasma ’ taxa.

The first record of a potential pest Orientus ishidae (Matsumura, 1902) (Hemiptera: Cicadellidae) in Poland

“…Th is phytoplasma is known as a causal agent of Peach X disease, which is common in North America but sporadic in Europe and Japan, and is considered to be a serious threat to trees and shrubs of the genus Prunus. Symptoms of this disease include changes in the color of leaf and fruit tissue, fruit deformation and shoot dieback (Davis et al 2013). Phytoplasma of the 16SrIII group was detected only once in Poland in spruce tissue, but it has not been confi rmed if it belongs to the same group as phytoplasmas causing drupaceous tree diseases (Kamińska and Śliwa 2008).…”

Maize bushy stunt phytoplasma affects native corn at high elevations in Southeast Mexico

“…The use of protein-encoding genes as part of the scheme of identification and classification of phytoplasmas has been suggested (Davis et al 2013). The groEL gene has been used to differentiate 'Ca.P.…”

“…Recently, other ribosomal and protein-encoding genes have been used to improve phytoplasma strain differentiation and/or to develop diagnostic methods (Lee et al 2010;Davis et al 2013;Dumonceaux et al 2014). The Cpn60-encoding gene has been successfully used as a marker for phytoplasma detection and differentiation (Mitrović et al 2011;Sugawara et al 2012;Alvarez et al 2014), and an approximately 550 bp portion of this gene, known as the chaperonin 60 universal target (cpn60UT) (Goh et al 1996) can be universally accessed and used to differentiate phytoplasmas (Pérez-López et al 2014;Dumonceaux et al 2014).…”

Molecular Identification of Phytoplasmas Infecting Diseased Pine Trees in the UNESCO-Protected Curonian Spit of Lithuania

“…More than 30 Candidatus (Ca.) Phytoplasma species have been described [17]. The high economic and societal impacts of phytoplasmal diseases can be attributed to their worldwide distribution, combined with the extremely wide range of plant families and species that are susceptible to phytoplasma infection.…”