"Candidatus Phytoplasma oryzae", a novel phytoplasma taxon associated with rice yellow dwarf disease.
ABSTRACT In addition to rice yellow dwarf (RYD) phytoplasma, several phytoplasmas infect gramineous plants, including rice orange leaf, bermuda grass white leaf, brachiaria grass white leaf and sugarcane white leaf phytoplasmas. To investigate whether the RYD phytoplasma is a discrete, species-level taxon, several isolates of the aforementioned phytoplasmas were analysed using PCR-amplified 16S rDNA sequences. Two RYD isolates, RYD-J(T) and RYD-Th, were almost identical (99.2 %), but were distinct (similarities of 96.3-97.9 %) from other phytoplasma isolates of the RYD 16S-group. The notion that the RYD phytoplasma constitutes a unique taxon is also supported by its unique insect vector (Nephotettix sp.), its unique host plant in nature (rice) and its limited geographical distribution (Asia). In Southern blot analysis, chromosomal and extrachromosomal DNA probes of the RYD phytoplasma reportedly did not hybridize with those of closely related phytoplasmas. These properties of the RYD phytoplasma clearly indicate that it represents a novel taxon, 'Candidatus Phytoplasma oryzae'.
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ABSTRACT: Here we investigate the endosymbiotic microbiota of the Macrosteles leafhoppers, M. striifrons and M. sexnotatus, known as vectors of phytopathogenic phytoplasmas. PCR, cloning, sequencing and phylogenetic analyses of bacterial 16S rRNA gene identified two obligate endosymbionts, Sulcia and Nasuia, and five facultative endosymbionts, Wolbachia, Rickettsia, Burkholderia, Diplorickettsia and a novel bacterium belonging to the Rickettsiaceae, from the leafhoppers. Sulcia and Nasuia exhibited 100% infection frequencies in the host species and populations, and were separately harbored within different bacteriocytes that constituted a pair of coherent bacteriomes in the abdomen of the host insects, as in other deltocephaline leafhoppers. Wolbachia, Rickettsia, Burkholderia, Diplorickettsia and the novel rickettsiaceae exhibited infection frequencies at 7%, 31%, 12%, 0% and 24% in M. striifrons, and at 20%, 0%, 0%, 20% and 0% in M. sexnotatus, respectively. Although undetected in the above analyses, nested PCR of 16S rRNA gene uncovered phytoplasma infections in 16% of M. striifrons and 60% of M. sexnotatus. Two genetically distinct phytoplasmas, namely 'Candidatus Phytoplasma asteris' associated with aster yellows and related plant diseases, and 'Candidatus Phytoplasma oryzae' associated with rice yellow dwarf disease, were identified from the leafhoppers. These results highlight strikingly complex endosymbiotic microbiota of the Macrosteles leafhoppers, and suggest ecological interactions between the obligate endosymbionts, the facultative endosymbionts and the phytopathogenic phytoplasmas within the same host insects, which may affect vector competence of the leafhoppers.Applied and Environmental Microbiology 06/2013; · 3.95 Impact Factor
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ABSTRACT: Yellow leaf disease (YLD) with phytoplasmal etiology is a serious disease of arecanut palm in India. The present study was undertaken to characterize the 16Sr DNA and secA gene sequences of arecanut YLD phytoplasma for 'Candidatus Phytoplasma' species assignment and 16Sr group/subgroup classification. Phytoplasma 16S rRNA gene was amplified using three sets of semi nested / nested primers, 1F7/7R3 - 1F7/7R2, 4Fwd/3Rev - 4Fwd/5Rev and P1/P7-R16F2n/R16R2 producing amplicons of 491 bp, 1150 bp and 1250 bp respectively from diseased samples. The amplicons were cloned and sequenced and representative partial sequences were deposited in GenBank (Acc no. GU552782, HM215624, JN967909). A BLAST search showed that the sequences had 99 % similarity with sugarcane white leaf phytoplasma (16SrXI) and napier grass stunt phytoplasma (16SrXI). The phylogenetic analysis based on 16S rDNA revealed the clustering of YLD phytoplasma with the rice yellow dwarf and Bermuda grass white leaf groups. The YLD phytoplasma F2nR2 sequence shared 97.5% identity with 'Candidatus Phytoplasma oryzae' and 97.8% identity with 'Candidatus Phytoplasma cynodontis'. Hence for finer differentiation we used the secA gene based phylogeny where the YLD phytoplasma clustered with napier grass stunt and sugarcane grassy shoot phytoplasmas, both belonging to the rice yellow dwarf group. Hence we are assigning the arecanut YLD phytoplasma as 'Candidatus Phytoplasma oryzae'-related strain. The virtual RFLP analysis of 1.2 Kb fragment of 16S rDNA (F2nR2 region) identified the arecanut YLD phytoplasma as a member of 16SrXI-B sub group. We are naming the phytoplasma as Indian YLD phytoplasma to differentiate from Hainan YLD phytoplasma which belongs to 16SrI group.INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 07/2012; · 2.11 Impact Factor
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ABSTRACT: This study addressed the taxonomic position and group classification of a phytoplasma responsible for virescence and phyllody symptoms in naturally diseased Madagascar periwinkle plants in western Malaysia. Unique regions in the 16S rRNA gene from the Malaysian periwinkle virescence (MaPV) phytoplasma distinguished the phytoplasma from all previously described 'Candidatus Phytoplasma' species. Pairwise sequence similarity scores, calculated through alignment of full-length 16S rRNA gene sequences, revealed that the MaPV phytoplasma 16S rDNA shared 96.5% or less sequence similarity with that of previously described 'Ca. Phytoplasma' species, justifying the recognition of the MaPV phytoplasma as a reference strain of a novel taxon, 'Candidatus Phytoplasma malaysianum'. The 16S rDNA F2nR2 fragment from the MaPV phytoplasma exhibited a distinct restriction fragment length polymorphism (RFLP) profile and the pattern similarity coefficient values were lower than 0.85 with representative phytoplasmas classified in any of the 31 previously delineated 16Sr groups; therefore, the MaPV phytoplasma was designated member of a new 16Sr group, 16SrXXXII. Phytoplasmas affiliated with this novel taxon and new group included diverse strains infecting periwinkle, coconut palm, and oil palm in Malaysia. Three phytoplasmas were characterized as representatives of three distinct subgroups, 16SrXXXII-A, 16SrXXXII-B, and 16SrXXXII-C, respectively.INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 04/2012; · 2.11 Impact Factor