Erysiphales

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Erysiphales

Erysiphales are an order

Order (biology)

In Biological classification used in biology, the order is a taxonomic rank between class and family . The superorder is a rank between class and order....
of ascomycete fungi. The order contains one family, Erysiphaceae. Many of them cause plant diseases called powdery mildew

Powdery mildew

Powdery mildew is a fungus disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of fungi in the order Erysiphales....
.

order contains one family

Family (biology)

In biological classification, family is a taxonomic rank. Exact details of formal nomenclature depend on the Nomenclature Codes which applies....
(Erysiphaceae), 28 genera

Genera

Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a Fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with Lisp Machines, Inc....
and approximately 100 species. Many imperfect fungi (fungi whose sexual reproduction is unknown) belong here, especially the genus Oidium
Oidium (genus)

Oidium is a genus of Deuteromycetes, where traditionally most anamorphs of the order Erysiphales are included. Most of them are plant pathogens causing different forms of powdery mildew, for example:...
. Recent molecular data have revealed the existence of six main evolutionary lineages.

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Encyclopedia

Erysiphales are an order

Order (biology)

Powdery mildew

Powdery mildew is a fungus disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of fungi in the order Erysiphales....
.

Systematics

The order contains one family

Family (biology)

In biological classification, family is a taxonomic rank. Exact details of formal nomenclature depend on the Nomenclature Codes which applies....
(Erysiphaceae), 28 genera

Genera

Clade

A clade is a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants.The term "monophyletic group" is used in this article in the conventional sense of "an a...
1 consists of Erysiphe
Erysiphe

Erysiphe is a genus of fungi. Many of the species in this genus are plant pathology which cause powdery mildew....
, Microsphaera, and Uncinula
Uncinula

Uncinula is a genus of fungi....
, 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
Sphaerotheca (fungi)

Sphaerotheca is a genus of ascomycete fungi that includes some important plant pathogens that cause forms of Powdery mildew....
, Podosphaera, and Cystotheca, which have Oidium subgenera Fibroidium and Setoidium mitosporic states. Clade 6 consists of Blumeria graminis
Blumeria graminis

Blumeria graminis is a fungus that causes powdery mildew on grasses, including cereals . It is the only species in the genus Blumeria....
, 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 superficial mycelium
Mycelium

Mycelium is the Vegetative reproduction part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the Fairy rings fungi....
which extracts nourishment from the host plant through specialized hyphae that penetrate the epidermal
Epidermis (botany)

The epidermis is a single-layered group of cells that covers plants leaf, flowers, roots and Plant stem. It forms a boundary between the plant and the external world....
cells of the host by means of absorbing organs called haustoria
Haustorium

In botany, a haustorium is the hyphal tip of a parasitic fungus or of the root of a parasitic plant , that penetrates the host's tissue, but stays outside the host cell membrane....
.

The teleomorphs are usually more distinctive and diverse than the anamorphs. Whether the asci
Ascus

An ascus is the sexual spore-bearing cell produced in Ascomycota fungi. On average, asci normally contain 8 ascospores, produced by a meiosis cell division followed, in most species, by a mitosis cell division....
are bitunicate or unitunicate (i.e. consisting of one or two layers), is as yet a matter of discussion.

The cleistothecia have the asci arranged in a hymenial
Hymenium

The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidium or ascus, which produce spores....
layer, resembling perithecia.

The cleistothecia are minute, usually not much more than 0.1 mm 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.

Erysiphales is notable for its beautiful appendage
Appendage

An appendage in the broadest sense is an additional or subsidiary part existing on, or added to, something which can generally still function if the appendage has never existed or is later provided or grown, or will still perform a primary function if the appendage is removed....
s which follow fractal
Fractal

A fractal is generally "a rough or fragmented Shape that can be split into parts, each of which is a reduced-size copy of the whole," a property called self-similarity....
geometry within Fibonacci number
Fibonacci number

In mathematics, the Fibonacci numbers are a sequence of numbers named after Leonardo of Pisa, known as Fibonacci . Fibonacci's 1202 book Liber Abaci introduced the sequence to Western European mathematics, although the sequence had been previously described in Indian mathematics....
s.

Life cycle

The infection of the host plant begins with the sexual ascospores, or the asexual conidia germinating on the surface of the plants leaf or stem, resulting in septate mycelium of uninucleate cells. In most powdery mildews only the epidermal

Epidermis (botany)

The epidermis is a single-layered group of cells that covers plants leaf, flowers, roots and Plant stem. It forms a boundary between the plant and the external world....
cells are attacked. The external mycelium gives rise to short, erect conidiophores, each of which bearing a single row of barrel-shaped spores, 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 parasite

Obligate parasite

An obligate parasite is a parasite organism that cannot live independently of its host ....
s on leaves and fruits of higher plants, causing diseases called powdery mildew

Powdery mildew

Powdery mildew is a fungus disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of fungi in the order Erysiphales....
s. Most attempts to grow them in culture

Microbiological culture

A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory conditions....
have failed.