Erysiphaceae
Uncinula tulasnei on a maple leaf
The powdery mildew fungi ( Erysiphales ) are a monotypic order of ascomycetes that contains only the family of Erysiphaceae. Within the class of Leotiomycetes they form a monophyletic group of obligate biotrophic ectoparasites that cause at various higher plants, including many crops and ornamental plants, powdery mildew. The fungi therefore have great economic importance.
Biology
Erysiphaceenarten grow superficially on their host. At the leaf surface of a mycelium, which appears as a white, wipe-clean coating forms. This form of so-called haustoria. These are special suction elements of powdery mildew, which anchor themselves in the cells of the epidermis. Thus, the fungus is supplied with nutrients. The haustoria penetrate Although the cell wall, but not the plasma membrane. By the removal of the sheet and ultimately withers nutrient drops. From the superficial mycelium conidiophores on which conidia ( spores summer ) are arranged to develop. The now spreading conidia provide for the mass multiplication during the growing season. Fruiting bodies emerge at the end of the growing season due to the merger varying degrees of fungal hyphae on the surface of infected plant organs. These so-called cleistothecia or Chasmothecien containing ascospores are smaller than conidia. The powdery mildew overwinters with its mycelium in the buds of infested plant and begins Selbiger to grow again with the bud. That is, it spreads again to a mesh and it forms conidiophores. The conidia are dispersed by the wind and form new foci of infection.
There is a fundamental difference to the likewise " mildew " said representatives of the order Peronosporales in which the grayish - bluish fungus develops on the underside of leaves and called downy mildew.
Ecological Significance
Powdery mildew is vital for some mycetophagous ladybug species. Thus, for example, the feed Sechzehnfleckige and the twenty-two -spot ladybird exclusively by mildew.
Genera and species of host plants (selection)
- Blumeria Blumeria graminis or Oidium monilioides ( anamorphic ) on cereals and grasses Blumeria has only recently as a separate genus and was counted earlier Erysiphe; the real one was graminis powdery mildew Erysiphe until then.
- Erysiphe betae on Beet; Mangold; sugar beet
- Erysiphe cichoracearum on cucumber, iceberg lettuce (rare); endive; Chicory ( seed carrier to plants); salsify
- Erysiphe communis on corn salad
- Erysiphe cruciferarum to Brussels sprouts, Chinese cabbage
- Erysiphe graminis on cereals
- Erysiphe heraclei of fennel; Carrot; Parsley Celery; parsnip
- Erysiphe necator or Oidium tuckeri ( Anamorphic ) on grapevines
- Erysiphe pisi on pea
- Erysiphe polygoni to clover, peas, and other legumes (rare), bush bean
- Erysiphe polyphaga on corn salad
- Microsphaera alphitoides at Oak
- Microsphaera azaleae to Rhododendron
- Microsphaera begoniae of tuberous begonias
- Microsphaera trifolii on pea shrubs, Geißklee, clover, lupins, grass pea, sweet clover
- Oidium lycopersicum on tomato
- Oidium ericinum of azaleas, rhododendrons and Erica
- Podosphaera aphanis to Strawberry
- Podosphaera aucupariae at Rowan
- Podosphaera leucotricha on apple
- Podosphaera macularis on hops
- Podosphaera mors - uvae of gooseberry and Ribes species
- Real Rosentaupilz ( Podosphaera pannosa ) to Rose; stone fruit
- Sphaerothecafuliginea of cucumber, endive
- Uncinula bicornis in Field Maple
- Uncinula necator also called powdery mildew on vine
- Uncinula tulasnei to Spitz Maple
In Taxoboxbild one of Uncinula tulasnei infested leaf Spitz maple (Acer platanoides ) is shown. Uncinula tulasnei is a specific ectoparasite of the pointed maple and endangers, regardless of the sometimes dramatic visual impact of the host tree not seriously. Therefore, a control with fungicides is not necessary. By burning the fallen foliage in autumn, the risk of reinfestation in the following year can be reduced.
This image shows the whitish mycelium the cleistothecia ( fruiting bodies ) than about 100 microns wide balls in different stages of maturity of yellow ( immature ) to black (ripe ). At this magnification, one can just make out a whitish fuzz appearing on some black cleistothecia formed colorless appendages. The form of these appendages at higher magnification allows the determination of the Art So these appendages are in Uncinula tulasnei sided curved in contrast to the parasitic on the field maple kind Uncinula bicornis, in which they are forked.
Phytopathologisches laboratory and resistance
As obligate biotrophic ectoparasites can be all powdery mildew fungi do not cultivate on nutrient media. This provides for the maintenance of pure cultures for resistance testing of varieties of different host species a problem, but because the resistance to powdery mildew pathogen in some host species is a distinctive feature of the variety, must be placed on the keeping clean of phytopathogens special attention. So Erysiphe pisi is cultivated under semi- sterile conditions on Fiederblaettern susceptible pea varieties for example. When host species, for which resistance does not serve to distinguish the varieties, but can be tested under natural infection conditions without further notice.