Phytoplasma
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 Vitis vinifera with "Ca. Phytoplasma vitis" infection
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"Ca. Phytoplasma allocasuarinae" |
Phytoplasma, formerly known as 'Mycoplasma-like organisms' or MLOs, are specialised wall-less bacteria that are obligate parasites of plant phloem tissue, and some insects. They can't be cultured in vitro in cell-free media. Phytoplasmas are pathogens of important crops causing a wide variety of symptoms that ranges from mild yellowing to death of infected plants. Characteristic symptoms of phytoplasma infection include discoloration of leaves, leaf curving, virescence, phyllody, witches' broom, stunting and general decline.
[edit] Phytoplasma taxonomy
The genus name Phytoplasma is yet to be formally recognised, and is currently at Candidatus status. There are currently 15 groups based on RFLP differences in the 16S rRNA gene sequence (16Sr groups). Each group include at least one Ca. Phytoplasma species, characterised by distinctive biological, phytopathological and genetic properties:
16SrI (Aster yellows group)
- Ca. Phytoplasma asteris
- Ca. Phytoplasma japonicum
16SrII (Peanut witches'-broom group)
- Ca. Phytoplasma aurantifolia
16SrIII (X-disease group)
- Ca. Phytoplasma pruni
16SrIV (Coconut lethal yellowing group)
- Ca. Phytoplasma palmae
- Ca. Phytoplasma castaneae
- Ca. Phytoplasma cocosnigeriae
16SrV (Elm yellows group)
- Ca. Phytoplasma ziziphi
- Ca. Phytoplasma vitis
- Ca. Phytoplasma ulmi
16SrVI (Clover proliferation group)
- Ca. Phytoplasma trifolii
16SrVII (Ash yellows group)
- Ca. Phytoplasma fraxini
16SrVIII (Luffa witches'-broom group)
- Ca. Phytoplasma luffae
16SrIX (Pigeon pea witches'-broom group)
- Ca. Phytoplasma phoenicium
16SrX (Apple proliferation group)
- Ca. Phytopalsma mali
- Ca. Phytoplasma pyri
- Ca. Phytoplasma prunorum
- Ca. Phytoplasma spartii
- Ca. Phytoplasma rhamnii
- Ca. Phytoplasma allocasuarinae
16SrXI (Rice yellow dwarf group)
- Ca. Phytopalsma oryzae
16SrXII (Stolbur group)
- Ca. Phytoplasma solani
- Ca. Phytoplasma australiense
16SrXIII (Mexican periwinkle virescence group)
- No Ca. Phytoplasma species defined yet
16SrXIV (Bermuda white leaf group)
- Ca. Phytoplasma cynodontis
16SrXV (Hibiscus witches'-broom group)
- Ca. Phytoplasma brasiliense
Phytoplasma australiense causes the disease "Sudden Decline" in New Zealand cabbage trees.
[edit] References
Ing-Ming Lee, Robert E. Davis, and Dawn E. Gundersen-Rindal. PHYTOPLASMA: Phytopathogenic Mollicutes. Ann. Rev. Microbiol., 2000, 54, 221-255. [1]
The IRPCM Phytoplasma/Spiroplasma Working Team - Phytoplasma taxonomy group: Candidatus Phytoplasma, a taxon for the wall-less, non-helical prokaryotes that colonize plant phloem and insects. Int. J. Syst. Evol. Microbiol., 2004, 54, 1243-1255. [2]
[edit] External links
- http://www.ba.ars.usda.gov/data/mppl/phytoplasma.html Phytoplasma Resource and phytoplasma classification database.
- Ohio State University publishes an informative site on this topic.
- First Internet Conference of Phytopathogenic Mollicutes includes several interesting articles on this topic.
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