Pythium porphyrae
Parasitic species of oomycete that causes red rot disease in seaweed From Wikipedia, the free encyclopedia
Pythium porphyrae, is a parasitic species of oomycete in the family Pythiaceae.[5] It is the cause of red rot disease or red wasting disease, also called akagusare (赤ぐされ) in Japanese.[1][6] The specific epithet porphyrae (πορφυρα) stems from the genus of one of its common hosts, Porphyra, and the purple-red color of the lesions on the thallus of the host.[7] However, many of its hosts have been moved from the genus Porphyra to Pyropia.
| Pythium porphyrae | |
|---|---|
| Scientific classification | |
| Domain: | Eukaryota |
| Clade: | Diaphoretickes |
| Clade: | Sar |
| Clade: | Stramenopiles |
| Phylum: | Oomycota |
| Order: | Peronosporales |
| Family: | Pythiaceae |
| Genus: | Pythium |
| Species: | P. porphyrae |
| Binomial name | |
| Pythium porphyrae | |
| Synonyms[2][3][4] | |
| |
Economic impact
Pythium porphyrae can destroy an entire crop of nori within three weeks.[8][9][6] It prefers low salinity and warm water (24-28 °C).[10][11][12][6] It will only grow in the 15-35 °C range.[13] Mild winters correlate with higher infestations and lower crop yields,[14] possibly due to decreased temperatures inducing the development of sex organs in the oomycete.[1] Losses can be combated by destroying diseased fronds and exposing thalli to the air for 3–4 hours daily.[6] The oospores can be spread in contaminated organic matter and the sporangia can spread through the water.[15]
Description
Summarize
Perspective
Pythium porphyrae has a mycelial thallus that is eucarpic, meaning only part of the thallus turns into sporangia.[15] It is primarily a facultative parasite of algae, but can also be saprobic.[15]
Its hyphae can grow up to 4.5 μm wide,[13][15] and are not septate.[1] On algae, the hyphae will extend through the cell wall.[1] It does not have haustoria not chlamydospores.[15] The appressoria are club-shaped.[15] It has sporangia that are unbranched, filamentous,[1][3] and non-inflated,[3] typically forming 6-17 zoospores per vesicle.[1][13][15] Encysted zoospores are 8-12 μm in diameter.[15] Hyphal swellings are intercalary and globose, from 12-28 μm in diameter.[15] Oogonia average 17 μm in diameter and are also intercalary and globose, but rarely are terminal.[13][15] In each oogonium are 1-2 diclinous antheridia[3][15][1] coming out far away from the oogonial stalk.[13] The antheridia's cells are clavate (club shaped) or globose.[1][13][15] The antheridia will be apical to the oogonial wall.[15] Sometimes there will be two antheridial cells on one stalk.[13] The yellowish oospores average 15 μm in diameter, have thick (~2 μm) walls, and are plerotic (fill the whole oogonium).[13][15] Conidia are spherical at 8.8-30.8 μm diameter, but rarely produced.[1]
Pythium porphyrae shares many physical traits with P. marinum and P. monospermum,[13] and appears to be most closely related to P. adhaerens.[2][3] However it has up to four diclinous antheridia and sometimes two antheridial cells per stalk; P. monospermum has 1-4 either diclinous or monoclinous antheridia and P. marinum has only a single diclinous antheridium.[13] P. monospermum and P. marinum also have oogonia terminally on short branches, yet in P. porphyrae they tent to be intercalary.[13]
In a laboratory it will grow 5 mm per day[3] on seawater-cornmeal agar with low aerial mycelium[15] and colorless colonies,[1] but will not grow at all on potato-carrot agar.[13]
Ecology
Pythium porphyrae has been found in Japan,[1] Netherlands, New Zealand,[2] and Korea, but this range is likely underreported.[15] It has a parasitic relationship with the following hosts. Though some species of Pyropia and Porphyra are susceptible to infection in their gametophytic phase, they are resistant in their Conchocelis (sporophytic) phase.[2]
- Bangia atropurpurea[15]
- Callophyllis adhaerens[15]
- Chondrus crispus[2][3]
- Gelidium elegans[15]
- Gloiosiphonia capillaris[15]
- Gracilaria spp.[15]
- Grateloupia turuturu[15]
- Griffithsia subcylindrica[15]
- Lomentaria hakodatensis[15]
- Mastocarpus papillatus[16]
- Polyopes affinis (Carpopeltis affinis)[15]
- Polysiphonia morrowii[15]
- Pterocladiella capillacea[15]
- Pyropia cinnamomea[2]
- Pyropia plicata[2]
- Pyropia suborbiculata[2]
- Pyropia tenera[2][10][15][1]
- Pyropia virididentata[2]
- Pyropia yezoensis[13][3][15][1]
- Rhodymenia intricata[15]
- Stylonema alsidii[15]
- Wrangelia tanegana[15]
Taxonomy
A 2005 study concerning a case of Pythiosis from a related species (P. insidiosum) indicated that P. porphyrae is related to P. dissotocum, P. myriotylum, P. volutum, and P. vanterpoolii.[17]
In 2004, molecular analysis of Pythium determined that P. porphyrae is in "Clade A" along with P. adhaerens, P. deliense, P. aphanidermatum, and P. monospermum[3] Clade A has two clusters, and P. porphyrae shares one with the species also originating on algae, P. adhaerens.[3]
A 2017 study of Pythium species in Clade A showed the following phylogenetic tree.[2] It further demonstrated that P. porphyrae and P. chondricola are the same species.[2][3] P. adhaerens may also be conspecific based solely on genetic comparison, but showed a number of physical differences that show it may be a separate but very closely related species.[2]
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See also
References
External links
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