Diseases
Erysiphales
Powdery mildew is a fungal disease manifesting as a white web-like coating on plant organs, leading to tissue necrosis, fruit deformation, and significant crop losses.
Mentioned in descriptions 33 570 varieties reference book.
Powdery mildew is caused by ectoparasitic fungi of the order Erysiphales, which develop primarily on the surface of leaves, shoots, and fruits. The initial white web-like coating eventually densifies into "powdery" cushions, upon which fungal fruiting bodies may form as dark spots. As a result of the infection, tissues turn yellow and become necrotic, fruits may crack, and leaves drop prematurely.
The intensity of disease development depends on a complex of factors: high relative humidity, moderate temperatures, the presence of dense canopy, and excessive nitrogen nutrition. Risks increase with alternating dry and wet weather. The harmfulness of the disease is expressed in a reduction of the leaf assimilation area, deterioration of crop quality, and a decrease in the general winter hardiness of crops.
Assessment of variety resistance is conducted under field conditions at various stages of vegetation, most often during the full heading phase. To classify the degree of infection, scoring systems or intensity scales in percentages are used, where varieties with up to 10% infection are considered highly resistant (R), 11 to 40% as moderately resistant (M), and more than 41% as susceptible (S). Variety resistance is ensured by genetic mechanisms that prevent colonization by the pathogen or limit the development of its mycelium.
Selection based on the description text, not official resistance ratings: such data is not available in registers. Mention indicates that the trait is discussed in the variety's sources; see the variety's profile for details on what is specifically stated.
Cucumis sativus L. · Cucumber
Rijk Zwaan Zaadteelt en Zaadhandel B.V.
Beta vulgaris Garden Beet Group · Garden beet
BEJO ZADEN
Cucumis sativus L. · Cucumber
Rijk Zwaan Zaadteelt en Zaadhandel B.V.
Lactuca sativa L. · Lettuce
Vilmorin-Mikado S.A.S.
Lactuca sativa L. · Lettuce
Vilmorin-Mikado S.A.S.
Cucumis sativus L. · Cucumber
Rijk Zwaan Zaadteelt en Zaadhandel B.V.
Poa pratensis L. · Kentucky bluegrass
PURE SEED TESTING
Hordeum vulgare L. · Barley
JOHANNA BERGER / STEFAN BERGER
Rosa L. · Rose
Poulsen Roser A/S
Rosa L. · Rose
Theo Adrianus Segers
Cucumis sativus L. · Cucumber
Rijk Zwaan Zaadteelt en Zaadhandel B.V.
Rosa L. · Rose
Poulsen Roser A/S
Rosa L. · Rose
Poulsen Roser A/S
Vitis vinifera L. · Common grape vine
Morgante Michele
Cucumis sativus L. · Cucumber
Rijk Zwaan Zaadteelt en Zaadhandel B.V.
Cucumis sativus L. · Cucumber
Enza Zaden, NL
Daucus carota L. · Carrot
HM Clause, F
Triticum durum Desf. · Durum wheat
S. A. FLORIMOND DESPREZ VEUVE ET FILS
x Triticosecale Wittm. ex A. Camus · Triticale
Stephanie Franck^^^Peter Franck^^^Norbert Starck
Lolium perenne L. · Perennial ryegrass
Limagrain Nederland B.V.
Cucurbita pepo L. · Field pumpkin
SEMILLAS FITO, S.A.
Hordeum vulgare L. · Barley
Hodowla Roslin Strzelce Sp z.o.o. Grupa IHAR
Hordeum vulgare L. · Barley
PLANT BREEDING INTERNATIONAL CAMBRIDGE
Triticum aestivum L. · Bread wheat
Hodowla Roslin Strzelce Sp z.o.o. Grupa IHAR