Phytophthora medicaginis

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Phytophthora medicaginis
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Chromista
Phylum: Oomycota
Order: Peronosporales
Family: Peronosporaceae
Genus: Phytophthora
Species:
P. medicaginis
Binomial name
Phytophthora medicaginis
Synonyms
Release of zoospores from sporangium Zoospore release.jpg
Release of zoospores from sporangium

Phytophthora medicaginis is an oomycete plant pathogen that causes root rot in alfalfa and chickpea. It is a major disease of these plants and is found wherever they are grown. P. medicaginis causes failure of stand establishment because of seedling death. [1] Phytophthora medicaginis is part of a species complex with Phytophthora megasperma .

Contents

Hosts and symptoms

P. medicaginis is a water mould pathogen that causes root rot and damping off of seedlings. P. medicaginis is specific to alfalfa and chickpea and can reside in soil or water, but since it is a water mold, it requires free water to infect another plant. This disease is most prevalent in newly seeded fields that experience flooding but can also be found in mature plants.

P. medicaginis commonly causes seedling death but if this pathogen is present in mature crops, P. medicaginis causes root rot which limits the plant's ability to acquire nutrients and water. [1]  This leads to secondary symptoms such as chlorosis, wilting, stunting, root decay, lesions and death. This disease is difficult to identify but reddish-brown or black root lesions will exist and oospores, sporangia, zoospores, antheridia, and oogonia are spore types that will be visible under a microscope. An ELISA test can confirm the presence of Phytophthora, but to confirm the species, a PCR test is effective. Several host factors will affect disease development including damage/stress to the plant and also the degree of resistance of host cultivar. [2]

Disease cycle

The disease cycle “starts” in the early spring as the oospores begin to germinate. Oospores are thick walled survival structures that allow the pathogen to survive winter. The oospores are then stimulated to germinate in the presence of free water and root exudates. [3] Germination produces zoospores and sporangia which can then release more zoospores that infect other seeds. [4] This is the asexual part of the cycle. This production of sporangia and zoospores happens until the end of the season when oogonia and antheridia engage in homothallic sexual reproduction to produce oospores once again. [5] Spore types are disseminated via water such as during flooding. A cool environment also favors disease transmission. [6]

Management

An integrated disease management program incorporating host resistance with disciplined cultural, chemical, and biological methods is the best way to control P. medicaginis. [5] The first several weeks are especially critical in the management of P. medicaginis as infected seeds die in a short amount of time. Control of alfalfa and chickpea is mostly possible using effective water management, use of resistant cultivars, proper crop rotation, and seed application of fungicides such as metalaxyl. [1] Effective water management is aimed at keeping the plants as dry as possible while still getting them enough water. Several ways to do this include assuring good drainage, avoiding excessive irrigation, and allowing plants to be dried by the wind. [2] Oospores can be spread by way of cultural practices on machinery, boots, and hooves. This spread can be limited by using proper sanitation before moving from an infected field to a disease free field. All of these control methods are aimed at stopping the initial infection of the seed/plant; water management also functions to limit the spread of zoospores because they may be spread by floods. Stopping the initial infection is important because this disease affects plants early on in their development as it quickly causes root rot and damping off. P. medicaginis can reside in fields as oospores for up to 3.5 years so the crop rotation must be at least 3 years long.

Related Research Articles

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Phytophthora sojae is an oomycete and a soil-borne plant pathogen that causes stem and root rot of soybean. This is a prevalent disease in most soybean growing regions, and a major cause of crop loss. In wet conditions the pathogen produces zoospores that move in water and are attracted to soybean roots. Zoospores can attach to roots, germinate, and infect the plant tissues. Diseased roots develop lesions that may spread up the stem and eventually kill the entire plant. Phytophthora sojae also produces oospores that can remain dormant in the soil over the winter, or longer, and germinate when conditions are favourable. Oospores may also be spread by animals or machinery.

<i>Phytophthora palmivora</i> Species of single-celled organism

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<i>Phytophthora cactorum</i> Species of single-celled organism

Phytophthora cactorum is a fungal-like plant pathogen belonging to the Oomycota phylum. It is the causal agent of root rot on rhododendron and many other species, as well as leather rot of strawberries.

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Pythium ultimum is a plant pathogen. It causes damping off and root rot diseases of hundreds of diverse plant hosts including corn, soybean, potato, wheat, fir, and many ornamental species. P. ultimum belongs to the peronosporalean lineage of oomycetes, along with other important plant pathogens such as Phytophthora spp. and many genera of downy mildews. P. ultimum is a frequent inhabitant of fields, freshwater ponds, and decomposing vegetation in most areas of the world. Contributing to the widespread distribution and persistence of P. ultimum is its ability to grow saprotrophically in soil and plant residue. This trait is also exhibited by most Pythium spp. but not by the related Phytophthora spp., which can only colonize living plant hosts.

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Pythium aristosporum is a species of pythium under the class oomycota that causes root dysfunction in creeping bentgrass.

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<i>Phytophthora capsici</i> Species of single-celled organism

Phytophthora capsici is an oomycete plant pathogen that causes blight and fruit rot of peppers and other important commercial crops. It was first described by L. Leonian at the New Mexico State University Agricultural Experiment Station in Las Cruces in 1922 on a crop of chili peppers. In 1967, a study by M. M. Satour and E. E. Butler found 45 species of cultivated plants and weeds susceptible to P. capsici In Greek, Phytophthora capsici means "plant destroyer of capsicums". P. capsici has a wide range of hosts including members of the families Solanaceae and Cucurbitaceae as well as Fabaceae.

Phytophthora fragariae is a fungus-like (oomycete) plant pathogen that causes red stele, otherwise known as Lanarkshire disease, in strawberries. Symptoms of red stele can include a red core in the roots, wilting of leaves, reduced flowering, stunting, and bitter fruit. The pathogen is spread via zoospores swimming through water present in the soil, released from sporangia.

Phytophthora megakarya is an oomycete plant pathogen that causes black pod disease in cocoa trees in west and central Africa. This pathogen can cause detrimental loss of yield in the economically important cocoa industry, worth approximately $70 billion annually. It can damage any part of the tree, causing total yield losses which can easily reach 20-25%. A mixture of chemical and cultural controls, as well as choosing resistant plant varieties, are often necessary to control this pathogen.

Phytophthora quercina is a papillate homothallic soil-borne plant pathogen causing root rot of oak tree species in Europe. It is associated with necrotic fine roots.

Globisporangium sylvaticum is a plant pathogen, an oomycete known to cause root rot and damping off in a multitude of species. These species include apples, carrot, cherry laurel, cress, cucumber, garlic, lettuce, pea, rhododendron, and spinach. Symptoms of infection include stunting, wilt, chlorosis, and browning and eventual necrosis of roots. The pathogen can by identified by the presence of thick, microscopic, round spores within the cells of the root.

Black rot on orchids is caused by Pythium and Phytophthora species. Black rot targets a variety of orchids but Cattleya orchids are especially susceptible. Pythium ultimum and Phytophthora cactorum are known to cause black rot in orchids.

References

  1. 1 2 3 Vandemark, G. J.; Barker, B. M. (2003-11-01). "Quantifying Phytophthora medicaginis in Susceptible and Resistant Alfalfa with a Real-Time Fluorescent PCR Assay". Journal of Phytopathology. 151 (11–12): 577–583. doi:10.1046/j.0931-1785.2003.00768.x. ISSN   1439-0434.
  2. 1 2 "Phytophthora medicaginis (Phytophthora root rot of lucerne)". www.cabi.org. Retrieved 2016-12-07.
  3. ↑ Erwin, D.C.; Al-Hamalawi, Z.A. (1985). "Components in Alfalfa Root Extract and Root Exudate that Increase Oospore Germination of Phytophthora megasperma f. sp. medicaginis" (PDF). Journal of Physiology and Biochemistry. 76: 508–513.
  4. ↑ Gray, Fred A; Koch, David (1996). "Biology and Management of Phytophthora Root Rot of Alfalfa" (PDF). Wyoming Extension.
  5. 1 2 "Phytophthora root rot of lucerne (Phytophthora medicaginis)". www.plantwise.org. Retrieved 2016-12-07.
  6. ↑ "Introduction to Oomycetes". www.apsnet.org. Retrieved 2016-12-07.
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