''Pythium porphyrae'', is a

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...

species of

oomycete The Oomycetes (), or Oomycota, form a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms within the Stramenopiles. They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction o ...

in the family

Pythiaceae Pythiaceae is a family of oomycetes. The family includes serious plant and animal pathogens in the genus '' Pythium''. The family was circumscribed by German mycologist Joseph Schröter in 1893. Lifecycle *Live on land ( terrestrial), and in wa ...

. It is the cause of red rot disease or red wasting disease, also called ' () in Japanese. The

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

''porphyrae'' () stems from the genus of one of its common hosts, '' Porphyra'', and the purple-red color of the lesions on the

thallus Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entir ...

of the host. However, many of its hosts have been moved from the genus ''Porphyra'' to '' Pyropia''.

Economic impact

''Pythium porphyrae'' can destroy an entire crop of

nori Nori is a dried edible seaweed used in Japanese cuisine, usually made from species of the red algae genus ''Pyropia'', including ''P. yezoensis'' and ''Pyropia tenera, P. tenera''. It has a strong and distinctive flavor, and is generally made in ...

within three weeks.ARASAKI, S. (1962). Studies on the artificial culture of Porphyra tenera Kjellm. 111. On the red wasting disease of Porphyra, especially on the physiology of the causal fungus Pythium sp.nov. n Japanese, English summary.Journal of the Agricultural Laboratory, Abiko, Japan. Central Research Institute of Electric Power Industry 3, 87-93 It prefers low

salinity Salinity () is the saltiness or amount of salt (chemistry), salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensio ...

and warm water (24-28 °C).SUTO, S., SAITO, Y., AKIYAMA, K. & UMEBAYASHI, 0. (1972). Text Book of Diseases and their Symptoms in Porphyra. n Japanese.Contribution E, Number I 8 of Tokai Regional Fisheries Research Laboratory, Japan. 37 pp.SAKURAI, Y., AKIYAMA, K. & SATO, S. (1974). On the formation and the discharge of zoospores of Pythium porphyrae in experimental conditions. n Japanese, English summary.Bulletin of the Tohoku Regional Fisheries Research Laboratory (33), I 19-27. It will only grow in the 15-35 °C range. Mild winters correlate with higher infestations and lower crop yields, possibly due to decreased temperatures inducing the development of sex organs in the oomycete. Losses can be combated by destroying diseased fronds and exposing thalli to the air for 3–4 hours daily. The oospores can be spread in contaminated organic matter and the

sporangia A sporangium (from Late Latin, ; : sporangia) is an enclosure in which spores are formed. It can be composed of a unicellular organism, single cell or can be multicellular organism, multicellular. Virtually all plants, fungus, fungi, and many ot ...

can spread through the water.

Description

''Pythium porphyrae'' has a

mycelial Mycelium (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fou ...

thallus that is eucarpic, meaning only part of the thallus turns into

. It is primarily a

facultative parasite A facultative parasite is an organism that may resort to parasitic activity, but does not absolutely rely on any host for completion of its life cycle. Examples of facultative parasitism occur among many species of fungi, such as family members ...

of algae, but can also be saprobic. Its

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...

e can grow up to 4.5 μm wide, and are not

septate In biology, a septum (Latin for ''something that encloses''; septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Human anatomy * Interatrial se ...

. On algae, the hyphae will extend through the cell wall. It does not have

haustoria In botany and mycology, a haustorium (plural haustoria) is a rootlike structure that grows into or around another structure to absorb water or nutrients. For example, in mistletoe or members of the broomrape family, the structure penetrates th ...

not chlamydospores. The appressoria are club-shaped. It has sporangia that are unbranched, filamentous, and non-inflated, typically forming 6-17

zoospore A zoospore is a motile asexual spore that uses a flagellum for locomotion in aqueous or moist environments. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Certain zoospores are ...

s per vesicle. Encysted zoospores are 8-12 μm in diameter. Hyphal swellings are intercalary and

globose This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary ...

, from 12-28 μm in diameter.

Oogonia An oogonium (: oogonia) is a small diploid cell which, upon maturation, forms a primordial follicle in a female fetus or the female (haploid or diploid) gametangium of certain thallophytes. In the mammalian fetus Oogonia are formed in lar ...

average 17 μm in diameter and are also intercalary and globose, but rarely are terminal. In each oogonium are 1-2 diclinous antheridia coming out far away from the oogonial stalk. The antheridia's cells are

clavate This glossary of entomology describes terms used in the formal study of insect species by entomology, entomologists. A–C A synthetic chlorinated hydrocarbon insecticide, toxic to vertebr ...

(club shaped) or globose. The antheridia will be apical to the oogonial wall. Sometimes there will be two antheridial cells on one stalk. The

yellow Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In t ...

ish oospores average 15 μm in diameter, have thick (~2 μm) walls, and are plerotic (fill the whole oogonium).

Conidia A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an asexual, non- motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also ...

are spherical at 8.8-30.8 μm diameter, but rarely produced. ''Pythium porphyrae'' shares many physical traits with '' P. marinum'' and '' P. monospermum'', and appears to be most closely related to '' P. adhaerens''. 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. ''P. monospermum'' and ''P. marinum'' also have oogonia terminally on short branches, yet in ''P. porphyrae'' they tent to be intercalary. In a

laboratory A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratories are found in a variety of settings such as schools ...

it will grow 5 mm per day on seawater-cornmeal agar with low aerial

mycelium Mycelium (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fo ...

and colorless colonies, but will not grow at all on potato-carrot agar.

Ecology

''Pythium porphyrae'' has been found in

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

Netherlands , Terminology of the Low Countries, informally Holland, is a country in Northwestern Europe, with Caribbean Netherlands, overseas territories in the Caribbean. It is the largest of the four constituent countries of the Kingdom of the Nether ...

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

, and

Korea Korea is a peninsular region in East Asia consisting of the Korean Peninsula, Jeju Island, and smaller islands. Since the end of World War II in 1945, it has been politically Division of Korea, divided at or near the 38th parallel north, 3 ...

, but this range is likely underreported. It has a parasitic relationship with the following hosts. Though some species of '' Pyropia'' and '' Porphyra'' are susceptible to infection in their

gametophytic A gametophyte () is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the sex ...

phase, they are resistant in their '' Conchocelis'' ( sporophytic) phase. *'' Bangia atropurpurea'' *'' Callophyllis adhaerens'' *''

Chondrus crispus ''Chondrus crispus''—commonly called Irish moss or carrageenan moss (Irish ''carraigín'', "little rock")—is a species of red algae which grows abundantly along the rocky parts of the Atlantic coasts of Europe and North America. In its fresh ...

'' *'' Gelidium elegans'' *'' Gloiosiphonia capillaris'' *''

Gracilaria ''Gracilaria'', also known as irish moss or ogonori, is a genus of red algae in the family Gracilariaceae. It is notable for its economic importance as an agarophyte meaning that it is used to make agar, as well as its use as a food for humans ...

'' spp. *'' Grateloupia turuturu'' *'' Griffithsia subcylindrica'' *'' Lomentaria hakodatensis'' *'' Mastocarpus papillatus'' *'' Polyopes affinis'' ('' Carpopeltis affinis'') *'' Polysiphonia morrowii'' *'' Pterocladiella capillacea'' *'' Pyropia cinnamomea'' *'' Pyropia plicata'' *'' Pyropia suborbiculata'' *'' Pyropia tenera'' *'' Pyropia virididentata'' *'' Pyropia yezoensis'' *'' Rhodymenia intricata'' *'' Stylonema alsidii'' *'' Wrangelia tanegana''

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''. In 2004, molecular analysis of ''Pythium'' determined that ''P. porphyrae'' is in "

Clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

A" along with '' P. adhaerens'', '' P. deliense'', '' P. aphanidermatum'', and '' P. monospermum'' Clade A has two clusters, and ''P. porphyrae'' shares one with the species also originating on

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

, ''P. adhaerens''. A 2017 study of ''Pythium'' species in Clade A showed the following

phylogenetic tree A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA. In ...

. It further demonstrated that ''P. porphyrae'' and ''P. chondricola'' are the same species. '' 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.

References

External links