Erysiphales are an

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

ascomycete Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The def ...

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

. The order contains one family, Erysiphaceae. Many of them cause plant diseases called

powdery mildew Powdery mildew is a fungus, fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of Ascomycota, ascomycete fungi in the order Erysiphales. Powdery mildew is one of the easier plant disea ...

Systematics

The order contains one

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

(Erysiphaceae), 28

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

and around 1000

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

. Many imperfect fungi (fungi whose sexual reproduction is unknown) belong here, especially the genus '' Oidium''. Recent molecular data have revealed the existence of six main evolutionary lineages.

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 ...

1 consists of '' Erysiphe'', '' Microsphaera'', and '' Uncinula'', all of which have an ''Oidium'' subgenus ''Pseudoidium'' mitosporic state. Clade 2 consists of '' Erysiphe galeopsidis'' and '' Erysiphe cumminsiana'' ( anamorphs in ''Oidium'' subgenus ''Striatoidium''). Clade 3 consists of ''Erysiphe'' species with anamorphs in ''Oidium'' subgenus ''Reticuloidium''. Clade 4 consists of ''Leveillula'' and ''Phyllactinia'', which have ''Oidiopsis'' and ''Ovulariopsis'' mitosporic states, respectively. Clade 5 consists of '' Sphaerotheca'', ''Podosphaera'', and ''Cystotheca'', which have ''Oidium'' subgenera ''Fibroidium'' and ''Setoidium'' mitosporic states. Clade 6 consists of '' Blumeria graminis'', which has an ''Oidium'' subgenus ''Oidium'' mitosporic state. Several morphological characters have been analysed and found not to conflict with the molecular data.

Characteristics

* Erysiphales have a superficial

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 ...

which extracts nourishment from the host plant through specialized

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 that penetrate the epidermal cells of the host by means of absorbing organs called haustoria. * The teleomorphs are usually more distinctive and diverse than the anamorphs. Whether the asci are bitunicate or unitunicate (i.e. consisting of one or two layers), is as yet a matter of discussion. * The cleistothecia (or ''chasmothecia'') have the asci arranged in a hymenial layer, resembling perithecia. The cleistothecia are minute, usually not much more than in diameter. From the outer wall of the cleistothecium specialised hyphae (appendages) grow out. The number of asci per ascoma varies, and is important in discriminating between genera.

Life cycle

The infection of the host plant begins with the sexual ascospores, or the asexual

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 ...

germinating on the surface of the plant's leaf or stem, resulting in

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 ...

mycelium of uninucleate cells. In most powdery mildews only the epidermal cells are attacked. The external mycelium gives rise to short, erect

conidiophore A conidium ( ; : conidia), sometimes termed an asexual chlamydospore or chlamydoconidium (: chlamydoconidia), is an Asexual reproduction, asexual, non-motility, motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word f ...

s, each of which bears a single row of barrel-shaped

spores In biology, a spore is a unit of sexual (in fungi) or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plant ...

, the youngest being at the base (the affected parts become thus covered with a forest of conidiophores assuming a white powdery appearance). The ripe spores become detached and are readily dispersed by the wind, causing fresh infection. In autumn the sexual cleistothecia are produced. The cleistothecia represent the resting (hibernating) stage of the pathogen. The ascospores remain dormant all winter to germinate in spring. When the asci expand they rupture the cleistothecia wall, throwing the ascospores into the air.

Ecology

Erysiphales are obligate parasites on leaves and fruits of higher plants, causing diseases called

s. Most attempts to grow them in

culture Culture ( ) is a concept that encompasses the social behavior, institutions, and Social norm, norms found in human societies, as well as the knowledge, beliefs, arts, laws, Social norm, customs, capabilities, Attitude (psychology), attitudes ...

have failed. Erysiphales have a nearly

cosmopolitan distribution In biogeography, a cosmopolitan distribution is the range of a taxon that extends across most or all of the surface of the Earth, in appropriate habitats; most cosmopolitan species are known to be highly adaptable to a range of climatic and en ...

, and have developed fungicide resistance just as widely. Total loss of function has resulted in some cases. Resistance management planning, use of multi-

mode of action In pharmacology and biochemistry, mode of action (MoA) describes a functional or anatomical change, resulting from the exposure of a living organism to a substance. In comparison, a mechanism of action (MOA) describes such changes at the molecul ...

fungicides, and altered frequency and quantity of application are needed to slow the progress of resistance.

Genera

As accepted by Wijayawardene et al. 2020 (with amount of species); * '' Arthrocladiella'' (1) * '' Blumeria'' (1) * '' Brasiliomyces'' (6) * '' Bulbomicroidium'' (1) * '' Caespitotheca'' (1) * '' Cystotheca'' (9) * '' Erysiphe ( Oidium)'' (478) * '' Golovinomyces'' (66) * '' Leveillula (Oidiopsis)'' (49) * '' Microidium'' (3) * '' Microsphaera'' (15) * '' Neoerysiphe'' (15) * '' Oidium'' (53) * '' Parauncinula'' (4) * '' Phyllactinia (Ovulariopsis)'' (117) * '' Pleochaeta'' (5) * '' Podosphaera'' (124) * '' Pseudoidium'' (80) * '' Queirozia'' (1) * '' Sawadaea'' (10) * '' Sphaerotheca'' (4) * '' Takamatsuella'' (1) * '' Typhulochaeta'' (4) * '' Uncinula'' (8) * '' Uncinuliella'' (1)

Systematics

Characteristics

Life cycle

Ecology

Genera

References

Further reading