Plasmopara halstedii
| Plasmopara halstedii | |
|---|---|
| Scientific classification | |
| Domain: | Eukaryota |
| (unranked): | SAR |
| Superphylum: | Heterokonta |
| Class: | Oomycetes |
| Subclass: | Incertae sedis |
| Order: | Peronosporales |
| Family: | Peronosporaceae |
| Genus: | Plasmopara |
| Species: | P. halstedii |
| Binomial name | |
|
Plasmopara halstedii (Farl.) Berl. & De Toni, (1888) |
|
| Synonyms | |
|
Peronospora halstedii Farl., (1882) |
|
Peronospora halstedii Farl., (1882)
Plasmopara helianthi Novot., (1962)
Plasmopara halstedii is a plant pathogen infecting sunflowers. The species is one of many pathogens commonly referred to as downy mildew.P. halstedii originated in North America.
P. halstedii oospores produce a thin wall which are resistant structures, sexually produced that are essential for its continuation. After entering an area, the eradication of the pathogen is difficult due to the formation of oospores, which can remain viable in soil for many years.
Plasmopara halstedii is an obligate biotroph that attacks the flowering plants of the Asteraceae family, found to infect the genus’ Helianthus, Bidens, Artemisia, and Xanthium. The pathogen has the strongest impact on Helianthus, degrading flower yields in the species H. argophyllus, H. debilis, H. petiolaris and H. annuus. H. annus, the common sunflower, is also the most common host of P. halstedii. Xanthium strumarium, the common cocklebur, and Ambrosia artemisiifolia, or ragweed, have been shown to act as significant wild hosts.
P. halstedii causes significant yield losses due to the production of infertile sunflowers. Infertility due to P. halstedii is a result of sporulation on the flowering bodies as well as seed damping off due to root infection. Other symptoms include plant stunting, chlorosis, root browning and alteration of secondary metabolism of infected plants.
As an oomycete, P. halstedii releases motile zoospores as secondary inoculum. In these cases, secondary infection symptoms are much less severe than primary symptoms. A sign of the disease is the “typical downy appearance” resulting from sporulation the plant surface.
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Wikipedia