''Phytophthora'' (from Greek (''phytón''), "plant" and (), "destruction"; "the plant-destroyer") is a genus of plant-damaging

oomycete Oomycota forms a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms, called oomycetes (). They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction of an oospore is the resul ...

s (water molds), whose member species are capable of causing enormous economic losses on crops worldwide, as well as

environmental damage Environmental degradation is the deterioration of the environment through depletion of resources such as quality of air, water and soil; the destruction of ecosystems; habitat destruction; the extinction of wildlife; and pollution. It is defin ...

in natural ecosystems. As well as impacting large scale agriculture, ''Phytophthora'' is a nuisance to garden and indoor plant hobbyists as well as bonsai artists. The cell wall of ''Phytophthora'' is made up of cellulose. The genus was first described by

Heinrich Anton de Bary Heinrich Anton de Bary (26 January 183119 January 1888) was a German surgeon, botanist, microbiologist, and mycologist (fungal systematics and physiology). He is considered a founding father of plant pathology (phytopathology) as well as the fou ...

in 1875. Approximately 170 species have been described, although 100–500 undiscovered ''Phytophthora'' species are estimated to exist.

Pathogenicity

''Phytophthora''

spp. In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate sexe ...

are mostly pathogens of

dicotyledon The dicotyledons, also known as dicots (or, more rarely, dicotyls), are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, t ...

s, and many are relatively host-specific parasites. ''

Phytophthora cinnamomi ''Phytophthora cinnamomi'' is a soil-borne water mould that produces an infection which causes a condition in plants variously called "root rot", "dieback", or (in certain '' Castanea'' species), "ink disease". The plant pathogen is one of the w ...

'', though, infects thousands of species ranging from

club moss Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching s ...

es, ferns,

cycad Cycads are seed plants that typically have a stout and woody ( ligneous) trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male or ...

s, conifers,

grass Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns and ...

es,

lilies ''Lilium'' () is a genus of herbaceous flowering plants growing from bulbs, all with large prominent flowers. They are the true lilies. Lilies are a group of flowering plants which are important in culture and literature in much of the world. M ...

, to members of many dicotyledonous families. Many species of ''Phytophthora'' are plant pathogens of considerable economic importance. ''

Phytophthora infestans ''Phytophthora infestans'' is an oomycete or water mold, a fungus-like microorganism that causes the serious potato and tomato disease known as late blight or potato blight. Early blight, caused by ''Alternaria solani'', is also often called "po ...

'' was the infective agent of the potato blight that caused the Great Famine of Ireland, and still remains the most destructive pathogen of

solanaceous The Solanaceae , or nightshades, are a family of flowering plants that ranges from annual and perennial herbs to vines, lianas, epiphytes, shrubs, and trees, and includes a number of agricultural crops, medicinal plants, spices, weeds, and orna ...

crops, including tomato and potato. The soya bean root and stem rot agent, ''

Phytophthora sojae ''Phytophthora sojae'' is an oomycete and a soil-borne plant pathogen that causes stem and root rot of soybean. This is a prevalent disease in most soybean growing regions, and a major cause of crop loss. In wet conditions the pathogen produce ...

'', has also caused longstanding problems for the agricultural industry. In general, plant diseases caused by this genus are difficult to control chemically, thus the growth of resistant cultivars is the main management strategy. Other important ''Phytophthora'' diseases are: * ''

Phytophthora agathidicida ''Phytophthora'' (from Greek (''phytón''), "plant" and (), "destruction"; "the plant-destroyer") is a genus of plant-damaging oomycetes (water molds), whose member species are capable of causing enormous economic losses on crops worldwide, ...

''—causes collar-rot on New Zealand kauri (''

Agathis australis ''Agathis australis'', commonly known by its Māori name kauri (), is a coniferous tree in the family ''Araucariaceae'', found north of 38°S in the northern regions of New Zealand's North Island. It is the largest (by volume) but not t ...

''), New Zealand's most voluminous tree, an otherwise successful survivor of the Jurassic * ''

Phytophthora cactorum ''Phytophthora cactorum'' is a fungal-like plant pathogen belonging to the Oomycota phylum. It is the causal agent of root rot on rhododendron and many other species, as well as leather rot of strawberries. . Hosts, symptoms, and diagnosis ''Phy ...

''—causes

rhododendron root rot ''Phytophthora cactorum'' is a fungal-like plant pathogen belonging to the Oomycota phylum. It is the causal agent of root rot on rhododendron and many other species, as well as leather rot of strawberries. . Hosts, symptoms, and diagnosis ''Phy ...

affecting rhododendrons, azaleas, and orchids, and causes bleeding canker in hardwood trees * ''

Phytophthora capsici ''Phytophthora capsici'' is an oomycete plant pathogen that causes blight and fruit rot of peppers and other important commercial crops. It was first described by L. Leonian at the New Mexico State University Agricultural Experiment Station in ...

''—infects

Cucurbitaceae The Cucurbitaceae, also called cucurbits or the gourd family, are a plant family consisting of about 965 species in around 95 genera, of which the most important to humans are: *''Cucurbita'' – squash, pumpkin, zucchini, some gourds *'' Lagen ...

fruits, such as

cucumber Cucumber (''Cucumis sativus'') is a widely-cultivated creeping vine plant in the Cucurbitaceae family that bears usually cylindrical fruits, which are used as culinary vegetables.squash Squash may refer to: Sports * Squash (sport), the high-speed racquet sport also known as squash racquets * Squash (professional wrestling), an extremely one-sided match in professional wrestling * Squash tennis, a game similar to squash but pla ...

* ''

''—causes cinnamon root rot affecting forest and fruit trees, and woody ornamentals including

arborvitae ''Thuja'' ( ) is a genus of coniferous tree or shrub in the Cupressaceae (cypress family). There are five species in the genus, two native to North America and three native to eastern Asia. The genus is monophyletic and sister to ''Thujopsis''. M ...

azalea Azaleas are flowering shrubs in the genus ''Rhododendron'', particularly the former sections '' Tsutsusi'' (evergreen) and '' Pentanthera'' (deciduous). Azaleas bloom in the spring (April and May in the temperate Northern Hemisphere, and Octo ...

Chamaecyparis ''Chamaecyparis'', common names cypress or false cypress (to distinguish it from related cypresses), is a genus of conifers in the cypress family Cupressaceae, native to eastern Asia (Japan and Taiwan) and to the western and eastern margins of t ...

dogwood ''Cornus'' is a genus of about 30–60 species of woody plants in the family Cornaceae, commonly known as dogwoods, which can generally be distinguished by their blossoms, berries, and distinctive bark. Most are deciduous trees or ...

, forsythia, Fraser fir, hemlock, Japanese holly,

juniper Junipers are coniferous trees and shrubs in the genus ''Juniperus'' () of the cypress family Cupressaceae. Depending on the taxonomy, between 50 and 67 species of junipers are widely distributed throughout the Northern Hemisphere, from the Arcti ...

Pieris Pieris may refer to: Organisms * ''Pieris'' (plant), the andromeda or fetterbush, a plant genus in the family Ericaceae * ''Pieris'' (butterfly), the garden whites, a butterfly genus in the family Pieridae * ''Pieris'', a synonym of the genus ...

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 nat ...

, Taxus,

white pine ''Pinus'', the pines, is a genus of approximately 111 extant tree and shrub species. The genus is currently split into two subgenera: subgenus ''Pinus'' (hard pines), and subgenus ''Strobus'' (soft pines). Each of the subgenera have been furth ...

American chestnut The American chestnut (''Castanea dentata'') is a large, fast-growing deciduous tree of the beech family native to eastern North America. As is true of all species in genus Castanea, the American chestnut produces burred fruit with edible nuts. ...

and Australian woody plants, especially eucalypt and banksia. * '' Phytophthora citricola''—causes root rot and stem cankers in citrus trees * ''

Phytophthora fragariae ''Phytophthora fragariae'' is a fungus-like (oomycete) plant pathogen that causes red stele, otherwise known as Lanarkshire disease, in strawberries. Symptoms of red stele can include a red core in the roots, wilting of leaves, reduced floweri ...

''—causes red root rot affecting strawberries * ''

'' causes the serious disease known as potato (late) blight: responsible for the Great Famine of Ireland. * '' Phytophthora kernoviae''—pathogen of

beech Beech (''Fagus'') is a genus of deciduous trees in the family Fagaceae, native to temperate Europe, Asia, and North America. Recent classifications recognize 10 to 13 species in two distinct subgenera, ''Engleriana'' and ''Fagus''. The ''Engle ...

and rhododendron, also occurring on other trees and shrubs including oak, and holm oak. First seen in Cornwall, UK, in 2003. * '' Phytophthora lateralis''—causes cedar root disease in Port Orford cedar trees * '' Phytophthora megakarya''—one of the cocoa

black pod disease Black pod disease is a protozoal disease of Cocoa trees. This pathogen if left untreated can destroy all yields; annually the pathogen can cause a yield loss of up to 1/3 and up to 10% of total trees can be lost completely. With the value of the ...

species, is invasive and probably responsible for the greatest

cocoa Cocoa may refer to: Chocolate * Chocolate * ''Theobroma cacao'', the cocoa tree * Cocoa bean, seed of ''Theobroma cacao'' * Chocolate liquor, or cocoa liquor, pure, liquid chocolate extracted from the cocoa bean, including both cocoa butter an ...

crop loss in Africa * '' Phytophthora multivora''—discovered in analysis of isolates with ''P. cinnamomi'' dieback infections of tuart forests of Southwest Australia, which were previously diagnosed as ''P. citricola''. The species was found occurring on many other taxa, so named ''multivora''. * ''

Phytophthora nicotianae ''Phytophthora nicotianae'' or black shank is an oomycete belonging to the order Peronosprales and family Peronosporaceae. Hosts and symptoms ''Phytophthora nicotianae'' has a broad host range comprising 255 genera from 90 families. Hosts inclu ...

''—infects onions * '' Phytophthora palmivora''—causes fruit rot in

coconut The coconut tree (''Cocos nucifera'') is a member of the palm tree family (Arecaceae) and the only living species of the genus ''Cocos''. The term "coconut" (or the archaic "cocoanut") can refer to the whole coconut palm, the seed, or the ...

s and

betel nut The betel (''Piper betle'') is a vine of the family Piperaceae, which includes pepper and kava. The betel plant is native to Southeast Asia. It is an evergreen, dioecious perennial, with glossy heart-shaped leaves and white catkins. Betel pla ...

s * ''

Phytophthora ramorum ''Phytophthora ramorum'' is the oomycete (a type of protist) plant pathogen known to cause the disease sudden oak death (SOD). The disease kills oak and other species of trees and has had devastating effects on the oak populations in California a ...

''—infects over 60 plant genera and over 100 host species; causes

sudden oak death James Green aka "Sudden" is a fictional character created by an English author Oliver Strange in the early 1930s as the hero of a series, originally published by George Newnes Books Ltd, set in the American Wild West era. Oliver Strange died i ...

* '' Phytophthora quercina''—causes oak death * ''

''—causes soybean root rot Research beginning in the 1990s has placed some of the responsibility for European forest die-back on the activity of imported Asian ''Phytophthoras''. In 2019, scientists in Connecticut were conducting experiments testing various methods to grow healthier Fraser trees when they accidentally discovered a new species of ''Phytophthora'', which they called ''Phytophthora abietivora''. The fact that these scientists so readily discovered a new species further suggests that there could be many more species waiting to be discovered.

Species

The NCBI lists: *'' Phytophthora acerina'' *''

'' **'' Phytophthora cactorum var. applanata'' *'' Phytophthora cactorum × hedraiandra'' *'' Phytophthora cajani'' *'' Phytophthora cambivora'' *'' Phytophthora capensis'' *''

'' *'' Phytophthora aff. capsici'' *'' Phytophthora captiosa'' *'' Phytophthora castaneae'' *'' Phytophthora castanetorum'' *'' Phytophthora chlamydospora'' *'' Phytophthora chrysanthemi'' *'' Phytophthora cichorii'' *'' Phytophthora aff. cichorii'' *''

'' **'' Phytophthora cinnamomi var. cinnamomi'' **'' Phytophthora cinnamomi var. parvispora'' **'' Phytophthora cinnamomi var. robiniae'' *'' Phytophthora citricola'' *'' Phytophthora aff. citricola'' *''

Phytophthora citrophthora ''Phytophthora citrophthora'', also known as brown rot of citrus, is a soil borne oomycete that infects several economically important citrus crops. A diagnostic symptom of ''P. citrophthora'' is gummosis, wherein lesions around the base of the t ...

'' **'' Phytophthora citrophthora var. clementina'' *'' Phytophthora aff. citrophthora'' *'' Phytophthora clandestina'' *'' Phytophthora cocois'' *'' Phytophthora colocasiae'' *'' Phytophthora condilina'' *''

Phytophthora constricta ''Phytophthora'' (from Greek (''phytón''), "plant" and (), "destruction"; "the plant-destroyer") is a genus of plant-damaging oomycetes (water molds), whose member species are capable of causing enormous economic losses on crops worldwide, ...

'' *'' Phytophthora cooljarloo'' *'' Phytophthora crassamura'' *''

Phytophthora cryptogea ''Phytophthora cryptogea'' is a species of water mould in the family Pythiaceae. It is a plant pathogen that infects several species of cultivated plants, including over 40 species of cultivated flowers.Olson, H. A., et al. (2011)Phylogenetic his ...

'' *'' Phytophthora aff. cryptogea'' *'' Phytophthora cuyabensis'' *'' Phytophthora cyperi'' *'' Phytophthora dauci'' *'' Phytophthora aff. dauci'' *''

Phytophthora drechsleri ''Phytophthora drechsleri'' is a plant pathogen with many hosts. Affected plants See: * List of potato diseases * List of maize diseases * List of almond diseases * List of apricot diseases * List of beet diseases * List of caneberries disease ...

'' **'' Phytophthora drechsleri var. cajani'' *'' Phytophthora elongata'' *'' Phytophthora cf. elongata'' *'' Phytophthora erythroseptica'' **'' Phytophthora erythroseptica var. pisi'' *'' Phytophthora aff. erythroseptica'' *'' Phytophthora estuarina'' *'' Phytophthora europaea'' *'' Phytophthora fallax'' *'' Phytophthora flexuosa'' *'' Phytophthora fluvialis'' *'' Phytophthora fluvialis × moyootj'' *'' Phytophthora foliorum'' *'' Phytophthora formosa'' *'' Phytophthora formosana'' *''

'' *'' Phytophthora aff. infestans'' *'' Phytophthora inflata'' *'' Phytophthora insolita'' *'' Phytophthora cf. insolita'' *'' Phytophthora intercalaris'' *'' Phytophthora intricata'' *'' Phytophthora inundata'' *'' Phytophthora ipomoeae'' *'' Phytophthora iranica'' *''

Phytophthora irrigata ''Phytophthora'' (from Greek (''phytón''), "plant" and (), "destruction"; "the plant-destroyer") is a genus of plant-damaging oomycetes (water molds), whose member species are capable of causing enormous economic losses on crops worldwide, ...

'' **'' Phytophthora nicotianae var. parasitica'' *'' Phytophthora nicotianae × cactorum'' *'' Phytophthora niederhauserii'' *'' Phytophthora cf. niederhauserii'' *'' Phytophthora obscura'' *'' Phytophthora occultans'' *'' Phytophthora oleae'' *'' Phytophthora ornamentata'' *'' Phytophthora pachypleura'' *'' Phytophthora palmivora'' **'' Phytophthora palmivora var. palmivora'' *'' Phytophthora parasitica'' **'' Phytophthora parasitica var. nicotianae'' **''

Phytophthora parasitica var. piperina ''Phytophthora'' (from Greek (''phytón''), "plant" and (), "destruction"; "the plant-destroyer") is a genus of plant-damaging oomycetes (water molds), whose member species are capable of causing enormous economic losses on crops worldwide, as ...

'' *'' Phytophthora parsiana'' *'' Phytophthora aff. parsiana'' *'' Phytophthora parvispora'' *'' Phytophthora × pelgrandis'' *''

Phytophthora phaseoli ''Phytophthora phaseoli'' is a plant pathogen which infects lima bean A lima bean (''Phaseolus lunatus''), also commonly known as the butter bean, sieva bean, double bean, Madagascar bean, or wax bean is a legume grown for its edible seeds or ...

'' *'' Phytophthora pini'' *'' Phytophthora pinifolia'' *'' Phytophthora pisi'' *'' Phytophthora pistaciae'' *'' Phytophthora plurivora'' *'' Phytophthora pluvialis'' *'' Phytophthora polonica'' *''

Phytophthora porri ''Phytophthora'' (from Greek (''phytón''), "plant" and (), "destruction"; "the plant-destroyer") is a genus of plant-damaging oomycetes (water molds), whose member species are capable of causing enormous economic losses on crops worldwide, ...

'' *'' Phytophthora primulae'' *'' Phytophthora aff. primulae'' *'' Phytophthora pseudocryptogea'' *'' Phytophthora pseudolactucae'' *'' Phytophthora pseudorosacearum'' *''

Phytophthora pseudosyringae ''Phytophthora pseudosyringae'' is a semi-papillate homothallic soil-borne plant pathogen causing root and collar rot of broadleaf tree species in Europe. It is associated with necrotic fine roots and stem necroses of ''Fagus sylvatica'' and ...

'' *'' Phytophthora pseudotsugae'' *'' Phytophthora aff. pseudotsugae'' *'' Phytophthora psychrophila'' *'' Phytophthora quercetorum'' *'' Phytophthora quercina'' *'' Phytophthora quininea'' *''

'' *'' Phytophthora rhizophorae'' *'' Phytophthora richardiae'' *'' Phytophthora riparia'' *'' Phytophthora rosacearum'' *'' Phytophthora aff. rosacearum'' *'' Phytophthora rubi'' *'' Phytophthora sansomea'' *'' Phytophthora sansomeana'' *'' Phytophthora aff. sansomeana'' *'' Phytophthora × serendipita'' *'' Phytophthora sinensis'' *'' Phytophthora siskiyouensis'' *''

Phytophthora vulcanica ''Phytophthora'' (from Greek (''phytón''), "plant" and (), "destruction"; "the plant-destroyer") is a genus of plant-damaging oomycetes (water molds), whose member species are capable of causing enormous economic losses on crops worldwide, as ...

Resemblance to fungi

''Phytophthora'' is sometimes referred to as a fungus-like organism, but it is classified under a different clade altogether: SAR supergroup (Harosa) (also under Stramenopila and previously under

Chromista Chromista is a biological kingdom consisting of single-celled and multicellular eukaryotic species that share similar features in their photosynthetic organelles (plastids). It includes all protists whose plastids contain chlorophyll ''c'', suc ...

). This is a good example of convergent evolution: ''Phytophthora'' is morphologically very similar to true fungi yet its evolutionary history is completely distinct. In contrast to fungi, SAR supergroup is more closely related to plants than to animals. Whereas fungal cell walls are made primarily of chitin, ''Phytophthora'' cell walls are constructed mostly of

cellulose Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall ...

. Ploidy levels are different between these two groups; ''Phytophthora'' species have diploid (paired) chromosomes in the vegetative (growing, nonreproductive) stage of life, whereas fungi are almost always haploid in this stage. Biochemical pathways also differ, notably the highly conserved

lysine Lysine (symbol Lys or K) is an α-amino acid that is a precursor to many proteins. It contains an α-amino group (which is in the protonated form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −CO ...

synthesis path.

Biology

''Phytophthora'' species may reproduce sexually or asexually. In many species, sexual structures have never been observed, or have only been observed in laboratory matings. In

homothallic Homothallic refers to the possession, within a single organism, of the resources to reproduce sexually; i.e., having male and female reproductive structures on the same thallus. The opposite sexual functions are performed by different cells of a si ...

species, sexual structures occur in single culture.

Heterothallic Heterothallic species have sexes that reside in different individuals. The term is applied particularly to distinguish heterothallic fungi, which require two compatible partners to produce sexual spores, from homothallic ones, which are capable of ...

species have mating strains, designated as A1 and A2. When mated,

antheridia An antheridium is a haploid structure or organ producing and containing male gametes (called ''antherozoids'' or sperm). The plural form is antheridia, and a structure containing one or more antheridia is called an androecium. Androecium is also t ...

introduce gametes into oogonia, either by the oogonium passing through the antheridium (amphigyny) or by the antheridium attaching to the proximal (lower) half of the oogonium (paragyny), and the union producing oospores. Like animals, but not like most true fungi, meiosis is gametic, and somatic nuclei are diploid. Asexual (mitotic) spore types are

chlamydospore A chlamydospore is the thick-walled large resting spore of several kinds of fungi, including Ascomycota such as '' Candida'', Basidiomycota such as '' Panus'', and various Mortierellales species. It is the life-stage which survives in unfavourable ...

s, and

sporangia 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 ...

which produce zoospores. Chlamydospores are usually spherical and pigmented, and may have a thickened cell wall to aid in their role as a survival structure. Sporangia may be retained by the subtending hyphae (noncaducous) or be shed readily by wind or water tension (caducous) acting as dispersal structures. Also, sporangia may release zoospores, which have two unlike flagella which they use to swim towards a host plant. Zoospores (and zoospores of ''

Pythium ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequent ...

'', also in the Peronosporales) recognize not only hosts but particular locations on hosts. ''Phytophthora'' zoospores recognize and attach to specific root surface regions. This is a high degree of specificity at an early stage of cell development.

References

External links

* [https://web.archive.org/web/20070506074931/http://www.ladybug.uconn.edu/factsheets/tp_05_phytophthora.html Abbey, Tim (2005) "Phytophthora Dieback and Root Rot" College of Agriculture and Natural Resources, University of Connecticut]
"''Phytophthora'' Canker – Identification, Biology and Management"
Bartlett Tree Experts Online Resource Library
"''Phytophthora'' Root Rot – Identification, Biology and Management"
Bartlett Tree Experts Online Resource Library
Dieback Working Group
– Western Australia {{Taxonbar, from=Q311294 Water mould plant pathogens and diseases Water mould genera