Tombusvirus-like associated RNAs (tlaRNAs) are positive-sense single-stranded RNAs found in plants co-infected with some viruses of the genus Polerovirus. Pod pepper vein yellows virus (PoPeVYV) was recently reported as a new recombinant polerovirus causing interveinal yellowing, stunting, and leaf rolling in Capsicum frutescens plants at Wenshan city, Yunnan province, China. The complete genome sequence of its associated RNA has now been determined by next-generation sequencing and reverse transcription (RT) polymerase chain reaction (PCR). PoPeVYV-associated RNA (PoPeVYVaRNA) (GenBank Accession No. MW323470) has 2970 nucleotides and is closely related to other group II tlaRNAs, particularly tobacco bushy top disease-associated RNA (TBTDaRNA, GenBank Accession No. EF529625). In infection experiments on Nicotiana benthamiana and C. frutescens plants, synergism between PoPeVYVaRNA and PoPeVYV was demonstrated, leading to severe interveinal yellowing of leaves and stunting of plants. The results provide further information on the genetic and biological properties of the various agents associated with pepper vein yellows disease (PeVYD).
During the period from 2011 to 2013, several plant diseases repeatedly occurred in vegetable crops grown 4 in Yuanmou County, Yunnan Province, China. Affected plants included cowpea, sword bean, string bean, 5 tomato, lettuce, and water spinach. The diseased plants exhibited symptoms of witches'-broom growth 6 and floral deformations, linking each disease to phytoplasmal infection. Phylogenetic and virtual RFLP 7 analyses of the phytoplasmal 16S rRNA gene sequences amplified from DNA of diseased plants revealed 8 that all of the individual strains present in the diverse vegetable plants were affiliated with a single 9 'Candidatus Phytoplasma' species ('Ca. Phytoplasma aurantifolia') and a single ribosomal subgroup (16SrII-A). While presence of subgroup 16SrII-A phytoplasma in this geographic region was reported previously, such widespread infections in diverse plant hosts are unveiled for the first time in this study. In pursuing the source of the infections, we found that areas surrounding the affected vegetable fields were extensively invaded by parthenium weeds (Parthenium hysterophorus); and many of the weed plants exhibited abnormal morphologies that were suspicious of, and later diagnosed with, phytoplasmal infections. Results from genotyping of 16S rRNA and lineage-specific immunodominant membrane protein genes revealed that the vegetable-infecting phytoplasmas and the parthenium weed phytoplasma belong to the same genetic lineage. The findings indicate that parthenium weed poses a substantial risk as a reservoir of phytoplasmal infection of nearby agricultural crops in the geographic region since the ecosystems of Yuanmou are insect-rich, and parthenium weed is known to attract diverse leafhoppers. Further studies are warranted to assess the impact of farmland invasions by the noxious weed and to devise practical measures for improved weed control.
A new cauliflower disease characterised by the formation of leaf‐like inflorescences and malformed flowers occurred in a seed production field located in Yunnan, a southwest province of China. Detection of phytoplasma‐characteristic 16S rRNA gene sequences in DNA samples from diseased plants linked the cauliflower disease to phytoplasmal infection. Results from phylogenetic and virtual restriction fragment length polymorphism analyses of the 16S rRNA gene sequence indicated that the cauliflower‐infecting agent is a ‘Candidatus Phytoplasma aurantifolia’‐related strain and is a new member of the peanut witches'‐broom phytoplasma group, subgroup A (16SrII‐A). Multilocus genotyping showed close genetic relationship between this cauliflower phytoplasma and a broad host range phytoplasma lineage found only in East Asia thus far. Molecular markers present in the secY and rp loci distinguished this phytoplasma from other members of the subgroup 16SrII‐A.
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