Pythium dissotocum explained

Pythium dissotocum is a plant pathogen infecting strawberry and rice.

Disease cycle

Pythium dissotocum is a polycyclic oomycete root rot capable of both sexual and asexual reproduction. In its mid-season asexual phase, P. dissotocum disperses by forming filamentous sporangia, which produce vesicles housing 10-75 motile zoospores.[1] [2] Vesicles open, releasing zoospores which contact host roots, encyst, and produce a germ tube which infects the host root, and begins formation of mycelium.[3] [4]

In sexual reproduction, if multiple mating types are present, hyphal antheridium can contact each other and undergo plasmogamy, merging their membranes near the end of growing season. After several steps of differentiation and meiosis, an oospore, the primary survival structure, is formed. These thick-walled oospores can remain dormant for many months, and will eventually germinate through two methods. A sporangium can be produced, which generates a cyst and releases zoospores, or the oospore can create a germ tube which can directly penetrate and infect a host. This disease cycle is extremely dependent on water for dispersal, making greenhouses, irrigation systems, and hydroponics especially prone to spread of P. dissotocum. [5]

Importance

P. dissotocum is primarily a water-borne pathogen, and as a result poses serious threats to plants grown via hydroponics[6] and by irrigation. With motile spores that can move quickly, infection spreads rapidly in water-logged crops and hydroponic systems. P. dissotocum can infect a large range of hosts, including many agricultural and horticultural crops like lettuce, spinach, peppers, parsnip, parsley, tomato, sugar cane, and carrot[7] [8] [9] [10] [11] [12] and hydroponic Cannabis sativa.[13] Other economic products are threatened by the presence of P. dissotocum, including tree nurseries,[14] [15] maize/corn, and soybeans. Infection of P. dissotocum can lead to significant loss of crop yield due to necrosis of roots, root lesions, chlorosis, and damping off.[16] [17] This results in severe economic loss for farmers growing both sustenance crops, and commercial products. The organism is found in many regions across the Americas, Europe, and Asia, meaning that increasing globalization could cause introduction of the pathogen to potentially vulnerable crops and ecosystems.

Diagnosis

RTPCR methods are available.[18]

Control

As a root rot, it tends to have more severe effects on young plants and seedlings, where it can damage and kill newly forming roots necessary for plant growth and nutrient acquisition.[19] As a result, many control methods involve limiting the amount of exposure early in the season. Effective measure include application of fungicides like mefenoxam and phosphonates, often in conjunction. Additionally, inoculation with Pseudomonas chlororaphis, a common biocontrol inoculant used in horticulture, has potential to suppress symptoms of P. dissotocum infection, but is currently inconsistent in current trials, and doesn't block colonization.[20] Like most root rots, P. dissotocum thrives in wet conditions. Preventing over-watering will help reduce infection in soil. Engaging in sanitation or fungicide treatment of tools and water can help reduce transmission and infection of P. dissotocum especially in irrigation or hydroponic systems.[21] If infection has occurred, recovery can sometimes occur by trimming off damaged roots, and sterilizing those that are still white and healthy.[22]

External links

Notes and References

  1. Dreschler. Charles. 1930. Some New Species of Pythium . Journal of the Washington Academy of Sciences. 20. 16. 398–418. 24523710.
  2. Van Der Plaats-Niterink. J. 22 December 1981. Monograph of the genus Pythium. 21. 7 December 2018. 1 December 2017. https://web.archive.org/web/20171201033032/http://www.westerdijkinstitute.nl/publications/1021/content_files/content.htm. dead.
  3. Web site: Pythium: Introduction, Structure and Reproduction. Naleesh. T. 2016-08-24. Biology Discussion.
  4. Schroeder. Kurtis L.. Martin. Frank N.. de Cock. Arthur W. A. M.. Lévesque. C. André. Spies. Christoffel F. J.. Okubara. Patricia A.. Paulitz. Timothy C.. January 2013. Molecular Detection and Quantification of Pythium Species: Evolving Taxonomy, New Tools, and Challenges. Plant Disease. 97. 1. 4–20. 10.1094/PDIS-03-12-0243-FE. 30722255.
  5. Raudales. Rosa E.. Parke. Jennifer L.. Guy. Charles L.. Fisher. Paul R.. Control of waterborne microbes in irrigation: A review. . 143. 9–28. 10.1016/j.agwat.2014.06.007. 2014. 2014AgWM..143....9R .
  6. Sutton . John Clifford . Sopher . Coralie Rachelle . Owen-Going . Tony Nathaniel . Liu . Weizhong . Grodzinski . Bernard . Hall . John Christopher . Benchimol . Ruth Linda . Etiology and epidemiology of Pythium root rot in hydroponic crops: current knowledge and perspectives . . 32 . 4 . 1990-01-06 . 0100-5405 . 10.1590/S0100-54052006000400001 . 307–321 . free .
  7. Web site: Pythium. Moorman. Gary. Penn State Extension.
  8. Corrêa, A. S., A. B. Rocha, S. A. Willani, J. M. Dariva, M. V. Souza, and M. G. Moraes. 2010. "Yellow Stunt, a Tobacco Disease Caused by Pythium Dissotocum, in Southern Parts of Brazil." Plant Disease 95 (3): 354–354. . 2011. 10.1094/PDIS-10-10-0759. 30743527. Corrêa. A. S.. Rocha. A. B.. Willani. S. A.. Dariva. J. M.. Souza. M. V.. Moraes. M. G.. Plant Disease. 95. 3. 354.
  9. McGehee, C., R. E. Raudales, and W. H. Elmer. 2018. "First Report of Pythium Dissotocum Causing Pythium Root Rot on Hydroponically Grown Lettuce in Connecticut." Plant Disease 102 (10): 2043.. 10.1094/PDIS-02-18-0365-PDN. free.
  10. Petkowski. J. E.. de Boer. R. F.. Norng. S.. Thomson. F.. Minchinton. E. J.. 2013-07-01. Pythium species associated with root rot complex in winter-grown parsnip and parsley crops in south eastern Australia. Australasian Plant Pathology . 42. 4. 403–411. 10.1007/s13313-013-0211-5. 2013AuPP...42..403P . 17354809.
  11. Botha. W. J.. Coetzer. R. L. J.. Species of Pythium associated with root-rot of vegetables in South Africa. South African Journal of Botany. 62. 4. 196–203. 10.1016/S0254-6299(15)30634-7. 1996. free.
  12. Trivilin. A.P.. Hartke. S. Moraes. M.G.. Components of different signalling pathways regulated by a new orthologue of AtPROPEP1 in tomato following infection by pathogens. Plant Pathology. 63. 5. 1110–1118. 10.1111/ppa.12190. 2014. free.
  13. Punja . Zamir K. . Rodriguez . Gina . Fusarium and Pythium species infecting roots of hydroponically grown marijuana (Cannabis sativa L.) plants . . Informa UK Limited . 40 . 4 . 2018-10-02 . 0706-0661 . 10.1080/07060661.2018.1535466 . 498–513. 91372504 . free . 2018CaJPP..40..498P .
  14. Weiland, Jerry E., Luisa Santamaria, and Niklaus J. Grünwald. 2014. "Sensitivity of Pythium Irregulare, P. Sylvaticum, and P. Ultimum from Forest Nurseries to Mefenoxam and Fosetyl-Al, and Control of Pythium Damping-Off." Plant Disease 98 (7): 937–42.. 2014. 10.1094/PDIS-09-13-0998-RE. 30708838. Weiland. J. E.. Santamaria. L.. Grünwald. N. J.. Plant Disease. 98. 7. 937–942. free.
  15. Weiland, Jerry E., Bryan R. Beck, and Anne Davis. 2013. "Pathogenicity and Virulence of Pythium Species Obtained from Forest Nursery Soils on Douglas-Fir Seedlings." Plant Disease 97 (6): 744–48.. 2013. 10.1094/PDIS-09-12-0895-RE. 30722598. Weiland. J. E.. Beck. B. R.. Davis. A.. Plant Disease. 97. 6. 744–748.
  16. Web site: Root Rot – Causes, Symptoms, Prevention, and Control. Elite Tree Care.
  17. Web site: UC IPM: UC Management Guidelines for Pythium Root Rot on Floriculture and Ornamental Nurseries. Koike. S. Wilen. C.
  18. 1 . 2013 . 97 . Schroeder . Kurtis . Martin . Frank . Cock . Arthur . Levesque . Andre . Spies . Christoffel . Okubara . Patricia . Paulitz . Timothy . American Phytopathological Society (APS) . . Molecular Detection and Quantification of Pythium Species: Evolving Taxonomy, New Tools, and Challenges . 0191-2917 . 10.1094/pdis-03-12-0243-fe . 4–20 . 73451469 . 30722255 .
  19. Book: Blancard, Dominique. 10.1016/B978-0-12-387737-6.50003-0. Tomato Disease. 2012. 978-0-12-387737-6. 3. Second.
  20. Chatterton. S.. Sutton. J. C.. Boland. G. J.. June 1, 2004. Timing Pseudomonas chlororaphis applications to control Pythium aphanidermatum, Pythium dissotocum, and root rot in hydroponic peppers. 10.1016/j.biocontrol.2003.11.001 . . 30. 2. 360–373. 2004BiolC..30..360C .
  21. Web site: Root Rots in the Garden. Hudelson. Brian. Jull. Laura. Wisconsin Horticulture.
  22. Web site: Recovering from Root Rot. Pennington.

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