View source for Pyrenophora tritici-repentis

{{Short description|Species of fungus}}
{{Use dmy dates|date=December 2023}}
{{Speciesbox
| image = Drechslera tritici-repentis (01).jpg
| genus = Pyrenophora
| species = tritici-repentis
| authority = (Died.) Drechsler, (1923)
| synonyms =
''Drechslera tritici-repentis'' <small></small><br />
''Drechslera tritici-vulgaris'' <small></small><br />
''Helminthosporium gramineum f.sp. tritici-repentis'' <small></small><br />
''Helminthosporium tritici-repentis'' <small></small><br />
''Helminthosporium tritici-vulgaris'' <small></small><br />
''Pleospora culmorum'' <small></small><br />
''Pleospora sarcocystis'' <small></small><br />
''Pleospora trichostoma'' <small></small><br />
''Pyrenophora tritici-vulgaris'' <small></small><br />
''Pyrenophora sarcocystis'' <small></small><br />
''Pyrenophora trichostoma'' <small></small><br />
''Pyrenophora tritici-vulgaris'' <small></small><br />
''Sphaeria culmorum'' <small></small><br />
''Sphaeria sarcocystis'' <small></small><br />
''Sphaeria trichostoma'' <small></small>
}}
'''''Pyrenophora tritici-repentis''''' ([[teleomorph]]) and ''Drechslera tritici-repentis'' ([[anamorph]]) is a necrotrophic [[fungal plant pathogen|plant pathogen of fungal origin]], phylum [[Ascomycota]].<ref name=Reem>{{cite journal |last1=Aboukhaddour |first1=Reem |last2=Turkington |first2=T. Kelly |last3=Strelkov |first3=Stephen E. |title=Race structure of ''Pyrenophora tritici-repentis'' (tan spot of wheat) in Alberta, Canada |journal= [[Canadian Journal of Plant Pathology]] |date=April 2013 |volume=35 |issue=2 |pages=256–268 |doi=10.1080/07060661.2013.782470|bibcode=2013CaJPP..35..256A |s2cid=85882209 }}</ref> The pathogen causes a disease originally named yellow spot but now commonly called tan spot, yellow leaf spot, yellow leaf blotch or helminthosporiosis.<ref name=Prescott>{{cite web |last1=Prescott |first1=J. M. |last2=Burnett |first2=P. A. |last3=Saari |first3=E. E. |last4=Ranson |first4=J. |last5=Bowman |first5=J. |last6=De Milliano |first6=W. |last7=Singh |first7=R. P. |last8=Bekele |first8=G. |title=Guide to Wheat Disease and Pests |url=http://wheat.pw.usda.gov/ggpages/wheatpests |website=wheat.pw.usda.gov |publisher=[[CIMMYT]] |access-date=4 December 2014 |archive-date=20 March 2017 |archive-url=https://web.archive.org/web/20170320144043/https://wheat.pw.usda.gov/ggpages/wheatpests |url-status=dead }}</ref><ref name="Helminthosporium-proc-1997">{{ cite conference | last1 = Duveiller | first1 = Etienne | last2 = Dubin | first2 = H.J. | last3 = Reeves | first3 = J. | last4 = McNab | first4 = A. | title = ''Helminthosporium'' Blights of Wheat: Spot Blotch and Tan Spot | website = [[International Maize and Wheat Improvement Center|CIMMYT]] | location = El Batan, Mexico | publication-place = México, D.F., México | date = 9–14 February 1997 | isbn = 970-648-001-3 | oclc = 39500836 | pages = viii+376 | s2cid = 82752566 | hdl = 10883/1229 | id = [[Invasive Species Compendium|CABI ISC]]# [http://www.cabi.org/isc/abstract/20001003003 20001003003] }}</ref> At least eight races of the pathogen are known to occur based on their virulence on a wheat differential set.<ref name=Gamba>{{cite journal |last1=Gamba |first1=Fernanda M. |last2=Strelkov |first2=Stephen E. |last3=Lamari |first3=Lakhdar |title=Virulence of ''Pyrenophora tritici-repentis'' in the Southern Cone Region of South America |journal= [[Canadian Journal of Plant Pathology]] |date=October 2012 |volume=34 |issue=4 |pages=545–550 |doi=10.1080/07060661.2012.695750|bibcode=2012CaJPP..34..545G |s2cid=84067227 }}</ref>
The tan (yellow) spot fungus was first described by Nisikado in 1923 in Japan.<ref name=Nisikado >{{cite journal |last=Nisikado |first=Yosikazu |title=Preliminary notes on yellow spot diseases of wheat caused by ''Helminthosporium tritici-vulgaris'' |journal= [[Inst Agric Biol]] |year=1928 |volume=4|pages=103–109}}</ref> and was later identified in Europe, Australia and the US, in the mid 1900s.<ref name=Faris>{{cite journal |last1=Faris |first1=Justin D. |last2=Liu |first2=Zhaohui |last3=Xu |first3=Steven S. |title=Genetics of tan spot resistance in wheat |journal= [[Theoretical and Applied Genetics]] |date=25 July 2013 |volume=126 |issue=9 |pages=2197–2217 |doi=10.1007/s00122-013-2157-y|pmid=23884599 |s2cid=1652404 }}</ref> The disease is one of the most important fungal disease on wheat and the fungal pathogen is found to infect in all parts of the world wherever wheat and other susceptible host crops are found.<ref name=Gamba /> ''P. tritici-repentis'' overwinters on stubble, and due to recent heavily no-till/residue retention cultural practices, increased incidence and yield loss of up to 49% has been witnessed if ideal conditions occur.<ref name=Faris /> It forms characteristic, dark, oval-shaped spots of [[necrosis|necrotic]] tissue surrounded by a yellow ring.<ref>[http://www.eumedia.es/user/articulo.php?id=650 eumedia.es – Control de enfermedades en cereales de invierno]. Web consulted 6 June 2008.</ref> It is responsible for losses that account for up to 30% of the crop,<ref>[http://www.engormix.com/MA-agricultura/trigo/articulos/manejo-enfermedades-trigo-t1668/998-p0.htm Manejo de las enfermedades del trigo]. Pérez Fernández, Jesús  & Corro Molas, Andrés. Web consulted 1 June 2008.</ref> due to its effects reducing [[photosynthesis]]. Pathogenesis and toxicity in ''P. tritici-repentis'' is controlled by a single [[gene]], transformations of this gene cause the pathogen to become benign when interacting with wheat.<ref>{{Cite web|url=http://www.plantcell.org/content/9/2/135.short |archive-url=https://web.archive.org/web/20141109051224/http://www.plantcell.org/content/9/2/135.short |archive-date=9 Nov 2014 |title=A single gene encodes a selective toxin causal to the development of tan spot of wheat.}}</ref> This has major implications for those in agriculture seeking to combat the effects of this fungus.
== Hosts and symptoms ==
Tan spot is found primarily on wheat, but is also found to infect other cereals and grasses including triticale, barley, and rye, but are less frequently affected.<ref name=Prescott /> Other grass species affected by the pathogen include Siberian wheat grass, sand bluestem, meadow brome, sheep fescue, June grass, little bluestem, green foxtail, needle and thread, and tall wheatgrass.<ref name=Krupinsky>{{cite journal |last1 = Krupinsky |first1 = J. M. |title = Grass Hosts of ''Pyrenophora tritci-repentis'' | year = 1992 |volume = 76 |issue = 1 |pages = 92–95 |url = http://www.apsnet.org/publications/PlantDisease/BackIssues/Documents/1992Articles/PlantDisease76n01_92.pdf |access-date = 4 December 2014 |doi = 10.1094/pd-76-0092 | publisher = [[American Phytopathological Society]] (APS) | journal = [[Plant Disease (journal)|Plant Disease]] }}</ref> While these are not necessarily agriculture crop hosts such as wheat, the pathogen is able to form and survive on many grass hosts, which can eventually venture into wheat fields. Other important grass susceptible hosts include smooth brome which can be found in pastures, as well as quack grass that is found in the environment and considered a weed in many agricultural crops. Lesions typically appear on both upper and lower leaf surfaces, and initially are tan to brown specks. Eventually, the tan to brown specks expand to larger irregular, oval, lens-shaped, ellipse, tan blotches with a yellow ring around them. The yellow ring is often referred to as a halo, yellow discoloration as chlorosis, and browning/death of leaf tissue as necrosis. The development of a dark brown to black spot in the center the lesion is characteristic of the disease.<ref name="Cereals Disease Encyclopedia">{{cite web |title=Cereals Disease Encyclopedia |url=http://archive.hgca.com/minisite_manager.output/3623/3623/Cereal%20Disease%20Encyclopedia/Diseases/Tan%20Spot%20(DTR).mspx?minisiteId=26 |website=archive.hgca.com |access-date=4 December 2014 |archive-url=https://web.archive.org/web/20141023063347/http://archive.hgca.com/minisite_manager.output/3623/3623/Cereal%20Disease%20Encyclopedia/Diseases/Tan%20Spot%20(DTR).mspx?minisiteId=26 |archive-date=23 October 2014 |url-status=dead }}</ref> If warmer temperatures and moist conditions persist, spores known as conidia will move up plant as secondary inoculum and can also infect head/spikes. Symptoms on the head are indistinct, but can cause brownish glumes, and grains can have a reddish appearance similar to the pathogen ''Fusarium''.<ref name="Cereals Disease Encyclopedia"/>
== Disease cycle ==
''P. tritici-repentis'' survives and overwinters as [[pseudothecia]] on stubble from the previous year's infected crop. The pseudothecia contain [[ascospore]]s (sexual spores). Such ascospores produced are large and typically dispersed by wind, but do not travel far due to their size. The ascospores land on leaf surfaces and begin to produce lesions by infection from appressorium and infection peg. The lesions initially formed by ascospores, known as condo, form atop of conidiophores, and can serve as primary inoculum to new plant/host via long distance wind dispersal. Condo can also serve as primary inoculum via rain splash to further more up primary host and re-infect. During and after maturation of the wheat crop, fungus can grow saprophytically as mycelium from the infected leaf blade, down the leaf sheath, and on to the stem where it will later form a pseudothecia.<ref name=Wegulo>{{cite web |last1=Wegulo |first1=S. N. |title=Tan Spot of Cereals |url=http://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Pages/TanSpot.aspx |website=apsnet.org |access-date=4 December 2014 |archive-url=https://web.archive.org/web/20140520212202/https://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Pages/TanSpot.aspx |archive-date=20 May 2014 |url-status=dead }}</ref> The disease develops over a wide temperature range, but is favored by warmer temperatures along with or followed by long rains, dew, or irrigation.<ref name=Wegulo/>
== Environment ==
The fungus requires 6-24+ hours of moisture to infect a leaf. This means that rain, significant dew or high canopy humidity are factors that can lead to infection. Optimal temperatures for symptom development range from {{convert|60-82|F|C}}.<ref name="TanSpot">De Wolf, Erick  "Tan Spot." Kansas State Plant Pathology (n.d):n.pag. Kansas State Extension, Apr. 2008. Web.</ref><ref name="Burrows">Burrows Mary, Grey William, and Olmstead Jeannie. "Fungal, Bacterial and Physiological Leaf Diseases of  Cereal Crops (wheat, Durum, Barley)." Fungal, Bacterial and Physiological Leaf Diseases of Cereal Crops (wheat, Durum, Barley)." (n.d.): n. pag. [[Montana State University]]. Web.</ref>
== Control ==
Since this disease can cause considerable yield loss, effective control is very important. The most effective method of long term control is crop rotation.<ref>Bockus, W.W., and M.M. Claassen. 1992.  Effects of crop rotation and residue management practices on severity of tan spot of winter wheat.  Plant Disease 76:633–636.</ref><ref name=Burrows/> There is a considerable difference in the fungal population after one year of rotation. Examples of non-host crops include mustard, flax, and soybean.<ref name=Wegulo/><ref name=TanSpot/> Some other control options include tillage. Foliar fungicides can also be used as control methods.<ref name=Wegulo/><ref>Carigano, M., S.A. Staggenborg, and J.P. Shroyer. 2008. Management practices to minimize tan spot in a continuous wheat rotation. Agronomy Journal 100:145–153.</ref> Since the top two leaves contribute the most to yield, it is important to protect them. Some effective fungicides include, but are not limited to, Headline, Quilt, and Stratego. There are however, resistant varieties that make most methods of control unnecessary.<ref name="Weg">Wegulo, Stephen N. Tan Spot of Wheat (2012): n. pag. University of Nebraska-Lincoln Extension, Institute of Agriculture and Natural Resources. University of Nebraska-Lincoln, Dec. 2012. Web.</ref> There is research to suggest that plant height may also influence the amount of disease able to form due to the pathogen. It suggests that shorter plants will have a lowered chance of infection.<ref name="Canada">"The Effect of Plant Height on Tan Spot on Durum Wheat in Southern Saskatchewan." National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web.</ref> This research has only been conducted in Canada however, and should lead to more research before being used as a control technique.
Out of all [[wheat pathogen]]s, ''Ptr'' is among the best studied.<ref name = "Advances" /> Among all [[necrotrophic]] pathogen of this crop, ''Ptr''{{'}}s and ''[[Parastagonospora nodorum]]''{{'}}s [[effector (biology)|effectors]] have become the best studied.<ref name = "Advances" >
{{ Cite journal
| date = 2018
| volume = 46
| pages = 14–18
| last2 = Solomon
| last1 = McDonald
| first2 = Peter
| first1 = Megan
| journal = [[Current Opinion in Microbiology]]
| title = Just the surface: advances in the discovery and characterization of necrotrophic wheat effectors
| doi = 10.1016/j.mib.2018.01.019
| pmid = 29452845
| s2cid = 3374561
}}
</ref>
=== Host resistance ===
Some [[plant disease resistance|resistance genes]] – especially against races 1 and 5, the most problematic in [[Kazakhstan]] – have been identified.<ref name="CIMMYT-resis-Kazakh-2021">{{cite web | last1=Dahm | first1=Madeline | title=Genome-wide association study puts tan spot-resistant genes in the spotlight | website=[[International Maize and Wheat Improvement Center|CIMMYT]] | date=29 July 2021 | url=http://www.cimmyt.org/news/genome-wide-association-study-puts-tan-spot-resistant-genes-in-the-spotlight/ | access-date=21 August 2021}}</ref><ref name="WHEAT-Kazakhstan-GWAS" />
== Importance ==
This disease is considered to be a very important one. According to the University of Nebraska, losses of 50 percent have been documented. This negatively impacts the profitability a farmer can hope to achieve within one year. Tan spot is recognized as "one of the major constraints of wheat production.<ref name=Weg/> This is also a very significant disease in Canada, creating similar yield losses annually. Tan spot is important enough and causing large enough yield losses to continually prompt new research.<ref name=Canada/> ''P. t-r.'' has caused serious epidemics in Kazakhstan since the 1980s with nearly half the national harvest being lost when there is an epidemic.<ref name="WHEAT-Kazakhstan-GWAS">{{cite web | first1=Madeline | last1=Dahm | title=Genome-wide association study puts tan spot-resistant genes in the spotlight | website=[[WHEAT (CGIAR)|WHEAT]] | url=http://wheat.org/genome-wide-association-study-puts-tan-spot-resistant-genes-in-the-spotlight/ | access-date=28 July 2021 | archive-date=22 September 2021 | archive-url=https://web.archive.org/web/20210922142934/https://wheat.org/genome-wide-association-study-puts-tan-spot-resistant-genes-in-the-spotlight/ | url-status=dead }}</ref>
== References ==
{{Reflist|30em}}
== External links ==
{{Commons category|Pyrenophora tritici-repentis}}
* [https://web.archive.org/web/20120216001119/http://www.oznet.ksu.edu/library/plant2/ep134.pdf Tan Spot, Kansas State University]
{{Taxonbar|from=Q289074}}
[[Category:Pyrenophora|tritici-repentis]]
[[Category:Fungal plant pathogens and diseases]]
[[Category:Wheat diseases]]
[[Category:Fungi described in 1923]]
[[Category:Fungus species]]