"Candidatus Phytoplasma australiense," a New Phytoplasma Taxon Associated with Australian Grapevine Yellows

Abstract

A phytoplasma was detected in naturally diseased 'Chardonnay' grapevines exhibiting symptoms of Australian grapevine yellows disease. The use of PCR designed to amplify phytoplasma DNA resulted in detection of phytoplasma DNA in all of the diseased plants examined; no phytoplasma DNA was detected in healthy seedling grapevines. The collective restriction fragment length polymorphism (RFLP) patterns of amplified 16s ribosomal DNA differed from the patterns described previously for other phytoplasmas. On the basis of the RFLP patterns, Australian grapevine yellows phytoplasma was classified as a representative of a new subgroup, designated subgroup 16SrI-J, in phytoplasma 16s rRNA group 16SrI (aster yellows and related phytoplasmas). A phylogenetic analysis in which parsimony of 16s rRNA gene sequences from this and other group 16SrI phytoplasmas was used identified the Australian grapevine yellows phytoplasma as a member of a distinct subclade (subclade xii) in the phytoplasma clade of the class Mollicutes. A phylogenetic tree constructed on the basis of 16s rRNA gene sequences was consistent with the hypothesis that there was divergent evolution of Australian grapevine yellows phytoplasma and its closet known relative, European stolbur phytoplasma (subgroup 16SrI-G), from a common ancestor. The unique properties of the DNA from the Australian grapevine yellows phytoplasma clearly establish that it represents a new taxon, "Candidatus Phytoplasma australiense."

Classification of phytoplasma strains in the elm yellows group (16SrV) and proposal of ‘Candidatus Phytoplasma ulmi’ for the phytoplasma associated with elm yellows

“…There is a consensus that each group should represent at least one separate species (Gundersen et al, 1994;Jung et al, 2002;Lee et al, 1998a;Seemüller et al, 1998). So far, of the nine 'Candidatus Phytoplasma' species proposed (Davis et al, 1997;Griffiths et al, 1999b;Jung et al, 2002Jung et al, , 2003Montano et al, 2001;Sawayanagi et al, 1999;Verdin et al, 2003;White et al, 1998;Zreik et al, 1995), two ('Candidatus Phytoplasma aurantifolia' and 'Candidatus Phytoplasma australasia') belong to subgroups in the peanut witches'-broom group (=group 16SrII) according the classification scheme proposed by Lee et al (1998a). The other six are 'Candidatus Phytoplasma fraxini' (16SrVII-A), 'Candidatus Phytoplasma australiense' (16SrXII-B), 'Candidatus Phytoplasma japonicum' (a strain closely related to members of 16SrXII), 'Candidatus Phytoplasma brasiliense' (16SrXV-A), 'Candidatus Phytoplasma castaneae' (most closely related to palm lethal yellows group 16SrIV), 'Candidatus Phytoplasma phoenicium' (16SrIV-B) and 'Candidatus Phytoplasma ziziphi' (16SrV-B).…”

“…This approach was found to be insufficient for differentiating many members of this group, of which several strains (or strain clusters) have been shown to be distinct according to biological or pathological properties. Many studies have focused on finer differentiation of phytoplasma strains associated with FD and grapevine yellows phytoplasma diseases in grapevine (Angelini et al, 2001;Daire et al, 1997;Davis et al, 1997;Martini et al, 1999Martini et al, , 2002. On the basis of analysis of a non-rDNA fragment, FD9, encoding a translocase protein (secY) and a partial ribosomal protein (rpl15) (Reinert, 1999), several distinct subgroups were identified.…”

'Candidatus Phytoplasma castaneae', a novel phytoplasma taxon associated with chestnut witches' broom disease.

“…Sequence analysis of 16S rDNA has also played an important role in the description of novel phytoplasma species (Zreik et al, 1995 ;Davis et al, 1997 ;White et al, 1998 ;Griffiths et al, 1999 ;Sawayanagi et al, 1999 ;Montano et al, 2001). This study used similar approaches to determine the phylogenetic relationships between the CnWB phytoplasma and other phytoplasmas.…”

‘Candidatus Phytoplasma asteris’, a novel phytoplasma taxon associated with aster yellows and related diseases

“…Gundersen et al (1994) proposed that the phytoplasma clade should be recognized as a novel genus within the class Mollicutes and that each subclade (or 16Sr group) represents at least a species. Thus far, eight 'Candidatus Phytoplasma' species have been proposed (Zreik et al, 1995;Davis et al, 1997;White et al, 1998;Griffiths et al, 1999;Sawayanagi et al, 1999;Montano et al, 2001;Jung et al, 2002;Verdin et al, 2003).…”