Phytophthora infestans (Phytophthora blight) | BCH-ORGA-SCBD-115642 | Organism | Biosafety Clearing-House

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Organism (ORGA)

last updated: 15 Jul 2020
Organism information
Phytophthora infestans
Kingdom Chromista
Phylum Oomycota
Class Oomycetes
Order Peronosporales
Family Peronosporaceae
Genus Phytophthora
Species Phytophthora infestans
  • Phytophthora blight
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Other (Water mould)
Characteristics related to biosafety
Toluca Valley, Mexico
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Cool nights, warm days, and extended wet conditions favour the development of severe epidemics. Sporulation can occur between 3-26°C, but optimally between 18-22°C. At temperatures between 21-26°C, sporangia form germ tubes for direct infection and at temperatures below 18° C, sporangia produce zoospores, which can each initiate an infection. Condensation also promotes the production of  sporangia.
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Worldwide - associated with the dispersal of potato seed tubers.
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Phytophthora infestans has been observed infecting roughly 90 plant species . However, the pathogen is most associated with potatoes (Solanum tuberosum) and tomatoes (Solanum lycopersicum).

The infection cycle begins with the development of asexual spore producing structures (sporangia) on the aerial parts of the plant or from oospores, which release zoospores (wind and rain dispersal) or germinate directly to initiate infection. Zoospores discard their flagella and synthesize a cell wall to form a cyst, which germinate within hours and enter into the host via openings such as stomata or form an appressorium-like germ tube to penetrate into the host. After penetration, a primary infection vesicle is formed and it is from which hyphae will emerge to colonize the plant host. The hyphae grow intercellularly, producing haustoria, which project into host cells, initiate an interaction between the pathogen and the host cell membrane and allow the pathogen to siphon nutrients from the host cells. As the infection spreads, P. infestans will produce sporophores, which will lead to the production of further sporangia and cause lethal lesions to be formed on the plant.

If two different mating types come into contact, sexual reproduction can occur and leads to the formation of thick-walled structures called oospores, which allow for survival and dispersal of the pathogen. In the absence of oospores, P. infestans can survive between crops as mycelium in infected tomato fruit or potato tubers.
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Additional Information
Phytophthora infestans is a fungus-like microorganism (water mould) that is most famously known as being the causal agent of the Irish potato famine.
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