Genus/species: Plasmopara viticola
Classification: Peronosporomycetes
Morphology:
- Cell: thick walls consisting of glucanes
- Colony: Malt agar: morphology unknown on medium
- Spore: biflagellated zoospores
- Zygote: oospore
- Ascus: not available
- Liquid Growth: Oospores germinate in water producing sporangium. The zoospores formed from the sporangium use the water for dispersal then proceed to form a film around the grapevine.
Physiological Traits:
Growth factors are weather-dependent and the fungus occurs naturally on many ornamental plants. The fungus gathers nutrients from cells within the plant it inhabits. The fungus has been inhibited by BABA (beta aminobutyric acid).
Ecological Traits:
Located in warm, humid climates and naturally occurs on wild grapevine species, such as Vitis aestivalis.
Distinguishing Features:
Depends upon water for various portions of its life cycle. The fungus utilizes the plants resources but does not kill the plant; therefore, the fungus is biotrophic.
Role in wine:
Thick white patches on the underlying side of a grape leaf. A disease agent responsible for downy mildew in grapevines. This infestation reduces wine grape yield by contributing to berry drop as well as berry rot. The overall quality of wine produced from infected berries is reduced.
Sensitivities:
- SO2:
- Sorbate:
- DMDC:
- pH:
- Acids: Phosphoric acid-based fungicides
- Ethanol:
- Anaerobiosis:
- Heat: Growth is temperature-dependent
References:
H. Konig et al. (eds.), Biology of Microorganisms on Grapes, in Must and in Wine. Springer-Verlag Berlin Heidelberg 2009.