Plasmopara obducens is a species of oomycete that causes Impatiens downy mildew. It was first described on Impatiens noli-tangere in Germany in 1877. Plasmopara obducens is known from native[where?] species of Impatiens since the 1800s, but outbreaks on cultivated varieties of Impatiens walleriana started in 2003 in the United Kingdom and in 2004 in the United States.[1] The outbreak spread worldwide by 2016.[2]
| Plasmopara obducens | |
|---|---|
Scientific classification 
| |
| Domain: | Eukaryota |
| Clade: | Diaphoretickes |
| Clade: | SAR |
| Clade: | Stramenopiles |
| Phylum: | Oomycota |
| Order: | Peronosporales |
| Family: | Peronosporaceae |
| Genus: | Plasmopara |
| Species: | P. obducens
|
| Binomial name | |
| Plasmopara obducens (J. Schröt.) J. Schröt., (1886)
| |
| Synonyms | |
| |
Morphology
editSporangiophores are an average of 373 (260-484) micrometers with the first branch appearing at 197 (120-271) micrometers. Sporangia are 16 (13-18) micrometers by 13 (11-16) micrometers. [3] Resting spores are globose with a diameter of 28 micrometers [1]
Disease symptoms
editInitially, leaves are stippled or yellowed. Infected leaves curl downward. A white down is often present on the underside of the leaves; buds and stems may also develop a down. Eventually, the leaves fall off the plant leaving just stems. [4] In about a week, the plants are dead.[2]
Taxonomy
editJ. Schröter originally placed the species in the genus Peronospora but later moved it to the genus Plasmopara. [5] Some authors believe the outbreaks on I. walleriana and I. balsamina are not caused by P. obducens but two new species P. destructor and P. velutina. [3]
References
edit- ^ a b Shishkoff, Nina (2019). "The oospore state of Plasmopara obducens, impatiens downy mildew". Mycologia. 111 (4): 632–646. doi:10.1080/00275514.2019.1601986. PMID 31136264. S2CID 169033508.
- ^ a b Derevnina, Lida; Petre, Benjamin; Kellner, Ronny; Dagdas, Yasin F.; Sarowar, Mohammad Nasif; Giannakopoulo, Artemis; De la Conception, Juan Carlos; Chaparro-Garcia, Angela; Pennington, Helen G.; van West, Pieter; Kamoun, Sophien (2016). "Emerging oomycete threats to plants and animals". Philosophical Transactions of the Royal Society B. 317.
- ^ a b Görg, Marlena; Ploch, Sebastian; Kruse, Julia; Kummer, Volker; Runge, Fabian; Choi, Young-Joon; Thines, Marco (2017). "Revision of Plasmopara (Oomycota, Peronosporales) parasitic to Impatiens". Mycological Progress. 16 (8): 791–799. doi:10.1007/s11557-017-1316-y. S2CID 20243718.
- ^ Rosetta, Robin (2014). "Downy mildew on impatiens". Retrieved July 4, 2019.
- ^ "Kryotogamen-Flora von Schlesien". 3–1. 1886: 129–256.
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External links
edit- Disease threatens garden impatiens; Surprising scientists and horticulturalists, once-mild downy mildew disease has struck the popular blooms in 33 states March 20, 2013 Vol.183 #8 Science News
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