Phytophthora cinnamomi
| Phytophthora cinnamomi | |
|---|---|
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| Scientific classification | |
| (unranked): | SAR |
| Superphylum: | Heterokonta |
| Class: | Oomycetes |
| Order: | Pythiales |
| Family: | Pythiaceae |
| Genus: | Phytophthora |
| Species: | P. cinnamomi |
| Binomial name | |
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Phytophthora cinnamomi Rands |
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Phytophthora cinnamomi is a soil-borne water mould that produces an infection which causes a condition in plants called "root rot" or "dieback". The plant pathogen is one of the world's most invasive species and is present in over 70 countries around the world.
Phytophthora cinnamomi lives in the soil and in plant tissues, can take different shapes and can move in water. During periods of harsh environmental conditions, the organisms become dormant chlamydospores. When environmental conditions are suitable, the chlamydospores germinate, producing mycelia (or hyphae) and sporangia. The sporangia ripen and release zoospores, which infect plant roots by entering the root behind the root tip. Zoospores need water to swim through the soil, therefore infection is most likely in moist soils. Mycelia grow throughout the root absorbing carbohydrates and nutrients, destroying the structure of the root tissues, "rotting" the root, and preventing the plant from absorbing water and nutrients. Sporangia and chlamydospores form on the mycelia of the infected root, and the cycle of infection continues to the next plant.
Early symptoms of infection include wilting, yellowing and retention of dried foliage and darkening of root color. Infection often leads to death of the plant, especially in dry summer conditions when plants may be water stressed.
Phytophthora cinnamomi is a diploid and heterothallic species with two mating types, A1 and A2. Sexual reproduction in heterothallic Phytophthora species ordinarily occurs when gametangia of opposite mating type interact in host tissue. This interaction leads to the formation of oospores that can survive for long periods in or outside the host. Phytophthora cinnamomi is also capable of self-fertilization (i.e. it can be homothallic). Phytophthora cinnamomi mating type A2 cultures can be induced to undergo sexual reproduction by exposure to damaging conditions, that is by exposure to hydrogen peroxide or mechanical damage.
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Wikipedia