| Erysiphales | |
|---|---|
 | |
| Powdery mildew | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Leotiomycetes |
| Order: | Erysiphales H.Gwynne-Vaughan, 1922 |
| Family: | Erysiphaceae Tul. &C.Tul., 1861 |
| Genera[1] | |
Genera (See Text) | |
Erysiphales are anorder ofascomycetefungi. The order contains one family,Erysiphaceae. Many of them cause plant diseases calledpowdery mildew.
The order contains onefamily (Erysiphaceae), 28genera and around 1000species.[2] Manyimperfect fungi (fungi whose sexual reproduction is unknown) belong here, especially the genusOidium.Recentmolecular data have revealed the existence of six main evolutionary lineages.Clade 1 consists ofErysiphe,Microsphaera, andUncinula, all of which have anOidium subgenusPseudoidiummitosporic state. Clade 2 consists ofErysiphe galeopsidis andErysiphe cumminsiana (anamorphs inOidium subgenusStriatoidium). Clade 3 consists ofErysiphe species with anamorphs inOidium subgenusReticuloidium. Clade 4 consists ofLeveillula andPhyllactinia, which haveOidiopsis andOvulariopsis mitosporic states, respectively. Clade 5 consists ofSphaerotheca,Podosphaera, andCystotheca, which haveOidium subgeneraFibroidium andSetoidium mitosporic states. Clade 6 consists ofBlumeria graminis, which has anOidium subgenusOidium mitosporic state. Several morphological characters have been analysed and found not to conflict with the molecular data.
The cleistothecia are minute, usually not much more than 0.1 millimetres (1⁄256 in) in diameter. From the outer wall of the cleistothecium specialised hyphae (appendages) grow out. The number of asci perascoma varies, and is important in discriminating between genera.
The infection of the host plant begins with the sexualascospores, or the asexualconidia germinating on the surface of the plant's leaf or stem, resulting inseptate mycelium ofuninucleate cells. In most powdery mildews only theepidermal cells are attacked. The external mycelium gives rise to short, erectconidiophores, each of which bears a single row of barrel-shapedspores, 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 sexualcleistothecia 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.
Erysiphales areobligate parasites on leaves and fruits of higher plants, causing diseases calledpowdery mildews. Most attempts to grow them inculture have failed.[3]
Erysiphales have a nearlycosmopolitan distribution,[4] and have developedfungicide resistance just as widely.[5] Total loss of function has resulted in some cases.[5] Resistance management planning, use of multi-mode of action fungicides, and altered frequency and quantity of application are needed to slow the progress of resistance.[5]
As accepted by Wijayawardene et al. 2020 (with amount of species);[2]
