Phytophthora cinnamomi

from Wikipedia, the free encyclopedia
Phytophthora cinnamomi
Warning notice on Phytophthora cinnamomi in Western Australia

Warning notice on Phytophthora cinnamomi in Western Australia

Systematics
Department : Egg mushrooms (Oomycota)
Class : Oomycetes
Order : Peronosporales
Family : Peronosporaceae
Genre : Phytophthora
Type : Phytophthora cinnamomi
Scientific name
Phytophthora cinnamomi
Rands

Phytophthora cinnamomi is a soil-borne representative of the egg fungus , which causes a disease in plants, which is called " root rot " ( English root rot, dieback ). The plant pathogen is one of the world's most aggressive invasive species and can be found in more than 70 countries.

Host range and symptoms

The host range of Phytophythora cinnamomi is very broad. The pathogen is found worldwide and causes diseases in hundreds of plant species. A number of economically important cultures are affected, e. B. Food suppliers such as avocado and pineapple , but also other commercially used species such as Fraser firs , spruce pines , frankincense pines , azaleas , camellias , box trees and many other tree species and ornamental trees . P. cinnamomi is a root pathogen that causes root rot and death of the host plant. Symptoms include: wilting, reduced fruit size, decreased yield, crown rot, discharge of plant sap , necrosis , leaf chlorosis , leaf curl and tree canker . Another symptom is that young shoots can die off and the exchange of substances between roots and shoots is interfered with. Older plants may either show no symptoms or show weak death despite severe root rot.

Life cycle and effects on plants

Phytophthora cinnamomi lives in the soil and in plant tissues, can take on different forms and move in water. During periods of unfavorable environmental conditions, the organism can develop resting forms in the form of chlamydospores . When the environmental conditions are again suitable, these chlamydospores "germinate" and create a mycelium (or hyphae ) and sporangia . The sporangia mature and release zoospores that attack the roots just behind the tips. To do this, they need water through which they can move; therefore, most infections occur in moist soils. The mycelium penetrates the entire root and absorbs carbohydrates and nutrients, destroys the structure of the root tissue, causes the roots to "rot" and prevents the plant from absorbing water and nutrients. Sporangia and chlamydospores form on the mycelium of the infected root and the cycle begins again with the infection of the next plant.

Early symptoms include wilting, yellowing and curling of dry leaves, and roots darkening. Infection often leads to plant death, especially in dry summers when the plants are suffering from drought stress .

Sexual reproduction

Phytophthora cinnamomi is a diploid and heterothallic species with two mating types (A1 and A2). Sexual reproduction in heterothallic Phytophthora species normally takes place when gametangia of opposite mating types meet in a host tissue. This interaction leads to the formation of oospores , which can survive for a long time inside or outside the host tissue. Phytophthora cinnamomi is also capable of self-fertilization (i.e. it can be homothallic ). Mating type A2 cultures of Phytophthora cinnamomi can be stimulated to circumvent sexual reproduction by exposing them to extremely adverse conditions, e.g. B. by contact with hydrogen peroxide or by mechanical destruction.

ecology

Phytophthora cinnamomi is a soil-borne pathogen that was first observed in tropical and subtropical countries. However, it can survive and develop even in moderate climates. P. cinnamomi is spread via zoospores and / or chlamydospores in the soil and in water under suitable conditions (warm and humid). The vectors include plants or parts of plants that contain mycelia or zoospores and that are transported over long distances; pieces of soil and debris blown by the wind; underground or surface runoff from precipitation; Machines and equipment that has been in contact with damp (infected) soil and has not been thoroughly cleaned; transported soil, including sand or gravel. Wildlife and domestic animals are also known to help spread the pathogen. A study on domestic pigs shows that they are transported in their digestive tract. People also spread the disease through their activities, namely logging, mining, hiking and traffic.

In the wild

When Phytophthora diseases spread to wild plant communities, many sensitive plant species are brought to death, resulting in a sustained decline in biodiversity and a drastic change in ecological processes. The composition of the plant communities can also be changed by increasing the number of resistant plants while decreasing the number of sensitive plants. Animal species dependent on the sensitive plant species are also reduced in number or eliminated entirely.

Forest damage presumably caused by Phytophthora cinnamomi was recorded in the USA around the beginning of the 19th century. An infection is the cause of the sudden death of a number of native tree species such as the American chestnut , for the small leaf disease ( English littleleaf disease ) in spruce pines ( Pinus echinata ), the Christmas tree disease ( English Christmas tree disease ) in nurseries Firs ( Abies fraseri ); Oak trees are affected from South Carolina to Texas .

Heathland in the Stirling Range ( Western Australia ) with a Phytophthora -infected valley in the middle distance

In Australia , Phytophthora cinnamomi infections are known as phytophthora dieback , dieback , jarrah dieback or cinnamon fungus , which affect a number of native plant species there and thus cause forest damage and sustainable changes to wilderness habitats.

Of particular interest are the infection and death of large forest and bush areas that protect endangered species in the extreme southwest of Western Australia . Many species of the genera Banksia , Darwinia , Grevillea , Leucopogon , Verticordia and Xanthorrhoea are affected. This in turn has an impact on the animals that depend on these plants as a food source or for their protection, such as the thin-tailed sleeping bag ( Cercartetus concinnus ) and the honey bag ( Tarsipes rostratus ). A study in the Perth area found that the deaths in the infected areas caused a significant change in the avian community, most notably in nectar-eating birds such as the harlequin honeyeater .

Small leaf disease ( English Littleleaf disease ) in pines ( Pinus spp.); the tree on the left shows no symptoms of infection, while the tree on the right has stunted needles that are typical of a Phytophthora cinnamomi infection.

Phytophthora cinnamomi is also a problem in the Mexican state of Colima , as several native oak and other plant species in their vicinity are affected. The pathogen also has the death of in California rare endemic shrub Arctostaphylos myrtifolia ( English Ione manzanita ) result.

In addition to destroying natural forest landscapes, Phytophthora cinnamomi can also infect fruit trees , nut trees and ornamental trees . Studies have shown that P. cinnamomi can attack the bear moss , ferns , cycads , conifers , rushes , grasses , lilies and a variety of other dicotyledonous plant species. This represents a remarkably broad host range for a plant pathogen and underlines the effectiveness of Phytophthora cinnamomi as an aggressive primary pathogen. The Invasive Species Specialist Group has the species on its list of the "100 Worst Invasive Species in the World."

In gardens and on agricultural land

This article or the following section is not adequately provided with supporting documents ( e.g. individual evidence ). Information without sufficient evidence could be removed soon. Please help Wikipedia by researching the information and including good evidence.

Phytophthora diseases affect numerous native and garden plants. The list includes a. Cinnamon , roses, azaleas and fruit trees. Because no cure is known, the pathogen that has invaded a garden cannot be easily removed and becomes a real problem.

Prevention procedures , e.g. B. Preventing intrusion include the planting of crops from uninfected areas (not the immediate area), the use of sterilized cultivation soil and the exclusive use of carefully composted mulch. Moving from one garden to the next can also spread the disease. Growing from seeds and cuttings is less risky because no soil is transported.

In Australia, many nurseries and nurseries are accredited in the Nursery Industry Accreditation Scheme Australia (NIASA) and use hygiene practices to avoid Phytophthora infection in their stock. Such practices prevent the disease from spreading through cultivated soil, plant material and water. Other preventive approaches include high growing banks, regular testing for Phytophthora infections, and quarantine areas for newly purchased plants.

Plants infested by Phytophthora typically die at the end of summer when they are most under stress. For this reason, infection is often confused with the effects of drought . A number of sensitive species are affected, but there are also resistant ones. If infection is suspected, the likely route of spread should be determined. The safest method of diagnosis is identification in the soil or in parts of plants by a laboratory.

An existing methods, Phytophthora get infection control consisting of injection or spraying the plants with a phosphonate - fungicide , use carefully composted mulch and the application of treatments before planting as solarization or biofumigation . Composted mulch effectively suppresses the pathogen and can protect healthy plants from infection. It is extremely important to stop the spread via infected soil, plants or water. Infested areas can be renatured with the help of resistant species.

Influence on avocado plantings

Phytophthora cinnamomi is the main cause of avocado tree death; the disease is under avocado growers as "root rot" ( English root rot ) known. Various varieties resistant to the disease have been bred since the 1940s to minimize damage. Infested trees generally die or become non-productive within three to five years. A study from the Fallbrook (California) area of ​​1960 correlated the higher level of root rot in avocados with poor ventilation and a higher proportion of clay in the soil.

Phosphonate herbicides

This article or the following section is not adequately provided with supporting documents ( e.g. individual evidence ). Information without sufficient evidence could be removed soon. Please help Wikipedia by researching the information and including good evidence.

Phosphonate salts such as potassium phosphonates were used as biodegradable fungicides to protect plants from dying off after Phytophthora infections. Calcium and magnesium phosphonates can also be used. No approach will completely eliminate Phytophthora , including phosphonates, although an integrated approach can control the spread and effects of the disease. Such an approach could encompass the strategic use of phosphonates, disinfectants, access controls, the removal of drainage barriers, the removal of the host plants and the establishment of excellent hygiene practices.

To be effective, the phosphonates must penetrate the plants' water transport system. This can be done via injections into the hosts or spraying onto the undergrowth. The phosphonates not only protect individual plants from infection with Phytophthora , but also support already infected plants in their regeneration.

management

P. cinnamomi has a wide range of hosts, making it difficult to control the spread of the disease. The pathogen appears to have the greatest impact in areas with a Mediterranean climate that have a mean annual rainfall of 600 millimeters, such as the Southeast Asian islands and parts of Australia. The pathogen appears to survive in the plants with no symptoms to tolerate. Effective management measures include a hygiene system, raised beds, crop rotations, soil solarization, soil cultivation and the creation of barriers. A hygiene system is difficult to maintain. It means using cleaned seeds, cleaning the stand, and using sandy soils with a low pH . Also, soil and water must be kept out of infested areas by using clean containers and equipment, installing underground drainage to prevent surface runoff, cultivating infested areas last, and harvesting healthy areas first.

Another way to contain the severity and spread of the disease is to cultivate it in raised beds. This can reduce the contact of the roots with the water. Promoting rapid drainage as moisture is a key factor in the establishment, spread, and longevity of the disease caused by the pathogen. Soil solarization can be used for some plants such as young avocados; In general, an integrated approach should be followed for avocado. This includes using the radiant heat from the sun, which is captured under transparent polyethylene films on the surface of the ground.

Chemical control measures include fumigation and various phosphonate herbicides. One potentially effective spore-dependent tactic is to do a fumigation before planting. For the eradication of chlamydospores, however, this would not be useful, as these are hidden deeper in the soil so that they cannot be reached by fumigation. Some experts do not recommend fumigation, as P. cinnamomi is often able to repopulate the treated soil, causing even more severe damage as the competing microorganisms in the soil are reduced by the fumigation. Phosphonate fungicides can increase the ability of trees to tolerate or resist the pathogen or to recover from infection with Phytophthora cinnamomi . Phosphonates have been used with some success in containing the disease and have been recognized as the main strategy for preventive crop protection. They are applied to the plants by spraying the leaves, application by plane or by direct injection.

Systematics

A distinction is made between the following varieties:

  • Phytophthora cinnamomi var. Cinnamomi
  • Phytophthora cinnamomi var. Parvispora
  • Phytophthora cinnamomi var. Robiniae

See also

literature

  • Jörg S. Pfadenhauer, Frank A. Klötzli: Vegetation of the Earth: Fundamentals, Ecology, Distribution , Springer-Verlag, 2015, page 325, ISBN 978-3-642-41950-8

Individual evidence

  1. ↑ a b c d Phytophthora cinnamomi (PHYTCN) . In: EPPO Global Database . Retrieved June 5, 2019.
  2. ↑ a b Phytophthora cinnamomi (Phytophthora dieback) . In: CABI Invasive Species Compendium . Retrieved June 5, 2019.
  3. ^ A b c Courtney Reuter: Phytophthora cinnamomi Rands . In: NCSU Plant Pathology . Retrieved June 5, 2019.
  4. ↑ Managing Phytophthora dieback in Bushland: A Guide for Land Holders and Community Conservation Groups , 5th edition, dieback Working Group, Australia 2009, ISBN 9780646493046 .
  5. ↑ C. Linde, A. Drenth, GH Kemp, MJ Wingfield, SL von Broembsen: Population Structure of Phytophthora cinnamomi in South Africa . In: Phytopathology . 87, No. 8, August 1997, pp. 822-827. doi : 10.1094 / PHYTO.1997.87.8.822 .
  6. ↑ RJ Reeves, RM Jackson: Stimulation of Sexual Reproduction in Phytophthora by Damage . In: Journal of General Microbiology . 84, No. 2, October 1974, pp. 303-310. doi : 10.1099 / 00221287-84-2-303 .
  7. ↑ David M. Cahill: TURNER REVIEW No. 17. Phytophthora cinnamomi and Australias biodiversity: impacts, predictions and progress towards control . In: Australian Journal of Botany . 56, No. 4, 2008. doi : 10.1071 / bt07159 .
  8. ↑ C. Robin, I. Smith, EM Hansen: Phytophthora cinnamomi . In: Forest Phytophthoras . 2, No. 1, December 28, 2012, ISSN  2164-7232 . doi : 10.5399 / osu / fp.2.1.3041 .
  9. ↑ Cinnamon Fungus . Parks Victoria. Archived from the original on August 1, 2008. Retrieved June 6, 2019.
  10. ↑ E. Groves, P. Hollick, G. Hardy, J. McComb: WA list of susceptible plants . Murdoch University.
  11. ^ Robert A. Davis, Leonie E. Valentine, Michael D. Craig, Barbara Wilson, Wesley J. Bancroft, Marnie Mallie: Impact of Phytophthora-dieback on birds in Banksia woodlands in south west Western Australia . In: Biological Conservation . 171, March 2014, pp. 136–144. doi : 10.1016 / j.biocon.2014.01.027 .
  12. ↑ Arctostaphylos myrtifolia Parry . In: GBIF Backbone Taxonomy . Retrieved June 6, 2019.
  13. ↑ Swiecki, EA Bernhardt: Diseases threaten the survival of Ione manzanita ( Arctostaphylos myrtifolia ) . In: Phytosphere Research . 2003. Retrieved June 6, 2019.
  14. ↑ 100 of the World's Worst Invasive Alien Species . Invasive Species Specialist Group. Retrieved June 6, 2019.
  15. ↑ RM Burns, JH Miner, CD Gustafson, GA Zentmyer, WA Thorn: Correlation of soil series and avocado root rot damage in the Fallbrook area . In: Yearbook , Volume 44. California Avocado Society, 1960, pp. 110-113.
  16. ↑ a b c David M. Cahill, James E. Rookes, Barbara A. Wilson, Lesley Gibson, Keith L. McDougall: Phytophthora cinnamomi and Australia's biodiversity: impacts, predictions and progress towards control . In: Australian Journal of Botany . 56, No. 4, July 7, 2008, ISSN  1444-9862 , pp. 279-310. doi : 10.1071 / bt07159 .
  17. ↑ a b Avocado Phytophthora Root Red . Retrieved June 6, 2019.

Other sources

  • Zentmyer, GA, 1980. Phytophthora cinnamomi and the Diseases it Causes, Monograph No. 10, APS Press, St Paul, Minnesota, US.

Web links