''Globisporangium sylvaticum'' is a plant pathogen, an oomycete known to cause

root rot Root rot is a condition in which anoxic conditions in the soil or potting media around the roots of a plant cause them to rot. This occurs due to excessive standing water around the roots. It is found in both indoor and outdoor plants, although ...

and damping off in a multitude of species. These species include apples,

carrot The carrot ('' Daucus carota'' subsp. ''sativus'') is a root vegetable, typically orange in color, though purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the wild carrot, ''Daucus carota'', nat ...

cherry laurel ''Prunus'' subg. ''Padus'' is a subgenus of ''Prunus'', characterised by having racemose inflorescences. ''Padus'' was originally a distinct genus, but genetic and morphological studies have shown that ''Padus'' is polyphyletic. It has been prop ...

, cress,

cucumber Cucumber (''Cucumis sativus'') is a widely-cultivated Vine#Horticultural climbing plants, creeping vine plant in the Cucurbitaceae family that bears usually cylindrical Fruit, fruits, which are used as culinary vegetables.

garlic Garlic (''Allium sativum'') is a species of bulbous flowering plant in the genus ''Allium''. Its close relatives include the onion, shallot, leek, chive, Allium fistulosum, Welsh onion and Allium chinense, Chinese onion. It is native to South A ...

, lettuce,

pea The pea is most commonly the small spherical seed or the seed-pod of the flowering plant species ''Pisum sativum''. Each pod contains several peas, which can be green or yellow. Botanically, pea pods are fruit, since they contain seeds and d ...

rhododendron ''Rhododendron'' (; from Ancient Greek ''rhódon'' "rose" and ''déndron'' "tree") is a very large genus of about 1,024 species of woody plants in the heath family (Ericaceae). They can be either evergreen or deciduous. Most species are nati ...

, and

spinach Spinach (''Spinacia oleracea'') is a leafy green flowering plant native to central and western Asia. It is of the order Caryophyllales, family Amaranthaceae, subfamily Chenopodioideae. Its leaves are a common edible vegetable consumed either f ...

. Symptoms of infection include

stunt A stunt is an unusual and difficult physical feat or an act requiring a special skill, performed for artistic purposes usually on television, theaters, or cinema. Stunts are a feature of many action films. Before computer generated imagery spec ...

ing, wilt, chlorosis, and browning and eventual

necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...

of roots. The pathogen can by identified by the presence of thick, microscopic, round spores within the cells of the root. The species was formerly placed in the genus ''Pythium'', but that genus has been divided into five distinct clades, each characterized by the morphology of the

sporangium A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cy ...

Disease cycle

''Globisporangium sylvaticum'' is known to be heterothallic, whereas other species in the

basionym In the scientific name of organisms, basionym or basyonym means the original name on which a new name is based; the author citation of the new name should include the authors of the basionym in parentheses. The term "basionym" is used in both botan ...

''Pythium'' were consistently known to be homothallic. Additionally,

oospores An oospore is a thick-walled sexual spore that develops from a fertilized oosphere in some algae, fungi, and oomycetes. They are believed to have evolved either through the fusion of two species or the chemically-induced stimulation of mycelia ...

have been shown to occur only in specific pairings of certain sporangial isolates, a finding which reinforces its heterothallic nature. Since the pathogen is an oomycete, it is known to produce several types of spores including sporangia, zoospores, and

. The pathogen begins its life cycle in the growth stage by constructing a well developed mycelium made of hyaline

hyphae 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 or ...

. This mycelium is the actively growing body of the pathogen and is responsible for the infection of the host, the subsequent colonization of the host plant, and the uptake of nutrients from its host. This hyphal growth can occur in two different ways within ''Globisporangium sylvaticum'', asexually or sexually. During its asexual life cycle the pathogen produces sporangium that occur terminally and intercalary, and are globose and thin walled in shape as well as sub-globose and lemon shaped, respectively. After a period of time biflagellate zoospores begin to develop within the protoplasm of the

and are subsequently released during the proper conditions. The motile zoospores proliferate through the vector medium until they reach the infection court of its host, in this case the seed or the roots. Once at the infection court, the zoospores encyst themselves on the root tips or seed of the host thereby infecting it and resulting in the occurrence of more mycelial growth and the eventual damping off/ root rot of the host plant. However, during the sexual lifecycle the pathogen, as previously mentioned, needs two different compatible isolates to form a

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...

structure called an oospore. The oospore is a survival structure for the pathogen which only germinates during non-adverse conditions. In the case of ''Globisporangium sylvaticum'', the oospore is globose, aplerotic(space between oospore wall and oogonium wall) and thick walled. The formation of the oospore is caused by the fusion of an antheridia and an

oogonium An oogonium (plural 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 larg ...

, the male and female reproductive parts, respectively. The antheridia in ''Globisporangium sylvaticum'' is characterized as being

diclinous Plant reproductive morphology is the study of the physical form and structure (the morphology) of those parts of plants directly or indirectly concerned with sexual reproduction. Among all living organisms, flowers, which are the reproductive st ...

and branched while the

oogonia An oogonium (plural 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 larg ...

are

intercalary Intercalation may refer to: *Intercalation (chemistry), insertion of a molecule (or ion) into layered solids such as graphite *Intercalation (timekeeping), insertion of a leap day, week or month into some calendar years to make the calendar follo ...

and sub-globose. After an oospore is formed as a result of the fusion between the aforementioned reproductive structures the pathogen continues to undergo cell division giving rise to the mycelium where both cycles repeat under the proper conditions.

Environment

A moist environment is required for the propagation and dispersal of ''Globisporangium sylvaticum''. The pathogen produces highly motile zoospores, which use

flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

for locomotion. In the presence of water, the zoospore will use its flagella to propel itself through the surrounding water, in the direction of a prospective infection court. In adverse environmental conditions, the pathogen exists in a structure called an oospore. This structure protects the pathogen for extended periods until conditions for its propagation are satisfied. Additionally, during ideal temperature conditions, it has been observed that optimal radial growth for ''Globisporangium sylvaticum'' occurs between 28 °C and 30 °C. During this temperature range the pathogen has been observed to grow 2.7 cm over a 24-hour period.

References

{{Taxonbar, from=Q7263903 Water mould plant pathogens and diseases Carrot diseases Leaf vegetable diseases Peronosporales Species described in 1967