Globisporangium sylvaticum
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| Globisporangium sylvaticum | ||||||||||||
| (WA Campb. & FF Hendrix) Uzuhashi, Tojo & Kakish. |
Globisporangium sylvaticum (syn. Pythium sylvaticum ) is a plant pathogen from the group of egg fungi , whichcauses seedling and root rot in a variety of plant species. The infected species include apples , carrots , cherry laurel , garden cress , cucumber , garlic , lettuce , peas , rhododendrons and spinach . Symptoms of infection include a. Dwarfing , wilting , chlorosis and browning and, finally,root death . The pathogen can be identified by the detection of thick, microscopic, round spores within the root cells.
The species was previously incorporated into the genus Pythium , but this has been split into five separate clades based on the morphology of the sporangia .
description
Globisporangium sylvaticum is heterothallic , whereas the species of the genus Pythium are all homothallic . In addition, the oospores were only detected in special pairings of some isolates, which again confirms their heterothallic nature. Since the pathogen belongs to the egg fungi, it produces different types of spores: sporangia , zoospores and oospores.
Life cycle
The species begins its life cycle at the growth stage by producing a well-developed mycelium from hyaline hyphae . This mycelium is the actively growing “body” of the organism and is responsible for the infection of the host , the colonization that follows and the absorption of nutrients from the host.
In Globisporangium sylvaticum, this hyphae growth can occur sexually or asexually.
With asexual reproduction , Globisporangium sylvaticum produces terminal or inserted sporangia. These are spherical and thin-walled or lemon-shaped. After a period of time, zoospores with two flagella begin to develop in the protoplasm of the sporangia, which are eventually released under suitable conditions. The mobile zoospores spread through the transmission medium until they reach the host's focus of infection, in the case of G. sylvaticum the germ or the roots. Once there, the zoospores encapsulate themselves in the root tips or in the germ and infect it. When the mycelium spreads in the host, seedling or root rot is ultimately caused.
However, as already mentioned , G. sylvaticum needs two different compatible isolates for sexual reproduction in order to form a diploid structure called an oospore. The oospore is a permanent stage of the species, which only germinates again under favorable conditions. In the case of Globisporangium sylvaticum , the oospore is spherical, aplerotic, i. H. with a space between wall and oospores oogone -Wand and thick-walled. The formation of the oospores is caused by the fusion of an antheridium with an oogonium, the male with the female part. Globisporangium sylvaticum's antheridia are diclinal and branched, while the oogonia are intercalary and almost spherical. After an oospore has formed, the organism continues to divide and allow the mycelium to grow so that both cycles of reproduction can repeat themselves under the appropriate conditions.
ecology
A moist environment is essential for Globisporangium sylvaticum to develop and spread . The pathogen produces highly mobile zoospores which use a flagellum for locomotion. When water is available, the zoospores use the flagellum like a propeller to move in the direction of a future source of infection. Under unfavorable conditions, the pathogen survives as an oospore. This will protect it for long periods of time until conditions are good enough for it to grow. It was also observed that optimal radial growth in G. sylvaticum occurs at temperatures between 28 ° C and 30 ° C. Within this range, 2.7 centimeters growth was observed over a 24 hour period.
Individual evidence
- ↑ a b A Desk Study to Review Global Knowledge on Best Practice of Oomycete Root-rot Detection and Control . Agriculture and Horticulture Development Board. April 2015. Retrieved December 5, 2016.
- ^ Pythium (Plant Diseases) . In: Plant Diseases (Penn State Extension) . Pennsylvania State University. Retrieved November 15, 2016.
- ↑ a b c d Shihomi Uzuhashi, Motoaki Tojo, Makoto Kakishima: Phylogeny of the genus Pythium and description of new genera . In: Mycoscience . 51, 2010, pp. 337-365. doi : 10.1007 / s10267-010-0046-7 .
- ↑ a b K. E. Papa, WA Campbell, FF Hendrix, Jr .: [www.jstor.org/stable/3757088 Sexuality in Pythium sylvaticum: Heterothallism .] In: Taylor & Francis, Ltd. (Ed.): Mycologia . 59, No. 4, July-August 1967, pp. 589-595. doi : 10.2307 / 3757088 .
- ^ Virginia Heffer, Mary L. Powelson, Kenneth B. Johnson: Oomycetes . American Pathological Society. Archived from the original on November 21, 2016. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved November 16, 2016.
- ↑ a b c d W. A. Campbell, FF Hendrix, Jr .: A New Heterothallic Pythium from Southern United States . In: Taylor & Francis, Ltd. (Ed.): Mycologia . 59, No. 2, March-April 1967, pp. 274-278. doi : 10.2307 / 3756800 .
- ↑ Yannis Raftoyannis, Michael W. Dick: Zoospore Encystment and Pathogenicity of Phytophthora and Pythium Species on Plant Roots . In: Microbiological Research . 161, No. 1, January 1, 2006, pp. 1-8. Retrieved July 11, 2019.
- ^ Pythium . In: Brill's New Pauly . Michigan State University. Integrated Pest Management.
