''Phytophthora'' (from

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

(''phytón''), "plant" and (), "destruction"; "the plant-destroyer") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

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

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

s. 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 se ...

are mostly pathogens of dicotyledons, 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 wo ...

'', 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,

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes exce ...

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 o ...

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 a ...

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 Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclu ...

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

s 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 "p ...

'' 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 produces ...

'', 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

cultivar A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture ...

s 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, as ...

''—causes collar-rot on

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

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 The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

* ''

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 ' ...

affecting rhododendrons, azaleas, and

orchids Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two largest families of flowering ...

, 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 cucumbers and

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''. ...

e, azalea, Chamaecyparis,

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 shru ...

, forsythia,

Fraser fir The Fraser fir (''Abies fraseri'') is a species of fir native to the Appalachian Mountains of the Southeastern United States. ''Abies fraseri'' is closely related to ''Abies balsamea'' (balsam fir), of which it has occasionally been treated a ...

, hemlock, Japanese holly, juniper, Pieris, rhododendron,

Taxus ''Taxus'' is a genus of coniferous trees or shrubs known as yews in the family Taxaceae. They are relatively slow-growing and can be very long-lived, and reach heights of , with trunk girth averaging . They have reddish bark, lanceolate, flat ...

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 further ...

, American chestnut and Australian woody plants, especially eucalypt and banksia. * ''

Phytophthora citricola ''Phytophthora citricola'' is a plant pathogen. It was first described by Kaneyoshi (Kenkichi) Sawada in 1927 when it was isolated from orange trees in present-day Taiwan. It has since been found causing disease on a wide variety of plants. Se ...

''—causes root rot and stem cankers in citrus trees * '' Phytophthora fragariae''—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 and rhododendron, also occurring on other trees and shrubs including

oak An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ''L ...

, and holm oak. First seen in Cornwall, UK, in 2003. * ''

Phytophthora lateralis ''Phytophthora lateralis'' is a soil-borne plant pathogen that causes cedar root disease in Lawson cypresses (''Chamaecyparis lawsoniana'') in Northern USA. This pathogen was first noted to cause disease in around 1920 on nursery stock near Sea ...

''—causes cedar root disease in Port Orford cedar trees * '' Phytophthora megakarya''—one of the cocoa black pod disease species, is invasive and probably responsible for the greatest cocoa 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 in ...

''—infects

onion An onion (''Allium cepa'' L., from Latin ''cepa'' meaning "onion"), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus ''Allium''. The shallot is a botanical variety of the onio ...

s * '' Phytophthora palmivora''—causes fruit rot in coconuts 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 p ...

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 ...

''—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 The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu a ...

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'' × ''cambivora'' is a plant pathogen that causes ink disease in European chestnut trees (''Castanea sativa''). Ink disease, also caused by ''Phytophthora cinnamomi'', is thought to have been present in Europe since the 18th cent ...

'' *'' 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 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 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 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 incl ...

'' **'' 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 plurivora'' is a very aggressive soil-borne plant pathogen, with worldwide distribution and a wide variety of hosts. It belongs to the class of oomycetes and is often described as a ‘fungal-like’ organism since they form a h ...

'' *'' 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, as ...

'' *'' Phytophthora primulae'' *'' Phytophthora aff. primulae'' *'' Phytophthora pseudocryptogea'' *'' Phytophthora pseudolactucae'' *'' Phytophthora pseudorosacearum'' *'' Phytophthora pseudosyringae'' *'' 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 stricta'' *'' Phytophthora sulawesiensis'' *''

Phytophthora syringae ''Phytophthora syringae'' is an oomycete plant pathogen known to infect nursery plants, particularly apple and pear Pears are fruits produced and consumed around the world, growing on a tree and harvested in the Northern Hemisphere in late ...

Resemblance to fungi

''Phytophthora'' is sometimes referred to as a

fungus A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from t ...

-like organism, but it is classified under a different clade altogether:

SAR supergroup The SAR supergroup, also just SAR or Harosa, is a clade that includes stramenopiles ( heterokonts), alveolates, and Rhizaria. The name is an acronym derived from the first letters of each of these clades; it has been alternatively spelled "RAS". ...

(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'', ...

). This is a good example of

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

: ''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 w ...

. 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 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 ...

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 ...

introduce gametes into

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 lar ...

, 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 cyc ...

which produce

zoospore A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Diversity Flagella types Zoospores may possess one or ...

s. 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 frequen ...

'', 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