Editing Texas root rot

{{Short description|Pathogenic fungus}}
{{Speciesbox
| image = Phymatotrichopsis omnivora.jpg
| genus = Phymatotrichopsis
| species = omnivora
| authority = (Duggar) Hennebert, (1973)
| synonyms = 
''Ozonium auricomum'' <small>Link [as 'auriconum'], (1809)</small><br>
''Ozonium omnivorum'' <small>Shear, (1907)</small><br>
''Phymatotrichum omnivorum'' <small>Duggar, (1916)</small>
}}
'''Texas root rot''' (also known as '''Phymatotrichopsis root rot''', '''Phymatotrichum root rot''', '''cotton root rot''', or, in the older literature, '''Ozonium root rot''') is a
[[pathogen|disease]] that is fairly common in [[Mexico]] and the southwestern [[United States]] resulting in sudden [[wilting|wilt]] and [[death]] of affected [[plant]]s, usually during the warmer months.  It is caused by a soil-borne [[fungus]] named '''''Phymatotrichopsis omnivora''''' that attacks the [[root]]s of susceptible plants. It was first discovered in 1888 by [[Louis Hermann Pammel|Pammel]] and later named by [[Benjamin Minge Duggar|Duggar]] in 1916.<ref name=":3">{{Cite web|last=Damicone|first=John P|date=January 2014|title=Phymatotrichum Root Rot|url=http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-2321/F-7621web.pdf|access-date=December 1, 2016|website=Oklahoma Cooperative Extension Service}}</ref><ref name=":1" />

A monograph of this disease, which includes a historical review, was written by R.B. Streets and H.E. Bloss in 1973.<ref>R.B. Streets and H.E. Bloss. 1973. Phymatotrichum Root Rot. Monograph #8. The [[American Phytopathological Society]] (APS), St. Paul, MN</ref>

== Host and symptoms ==
''Phymatotrichopsis omnivora'' is a [[necrotrophic]] fungal pathogen that has a very broad host range, attacking almost 2000 [[dicot]]yledonous species. It inhabits alkaline, [[calcareous soil]]s in southwestern United States.<ref name=":0">{{Cite web|url=http://aces.nmsu.edu/pubs/_a/a229.pdf|title=Phymatotrichum Root Rot|last=Goldberg|first=Natalie|date=2005|website= [[New Mexico State College of Agriculture]], Consumer and Environmental Sciences|access-date=17 November 2016}}</ref> It particularly targets dicots as most [[monocot]]s are immune.<ref name=":5">{{Cite web|last=Olson|first=Mary|date=February 2000|title=Cotton (Texas) Root Rot|url=http://cals.arizona.edu/pubs/diseases/az1150.html|access-date=1 December 2016|website=Cooperative Extension, College of Agriculture & Life Sciences, The [[University of Arizona]] }}</ref> Economically important plant hosts affected by the pathogen include: [[peanut]]s, [[cotton]], [[alfalfa]], [[apple]], [[pecan]]s, and [[ornamental tree]]s.

First [[symptom]] of disease is often [[chlorosis]] of the leaves then followed by browning and wilting. Two weeks after the first symptoms appear, the plant dies.<ref name=":0" /> In the field, infected cotton plants exhibit wilting in the mid to late summer form large circular patches and later die. Upon closer examination, the host plant's vascular system show extensive discoloration.<ref name=":0" /> Beneath the soil surface, other observable signs are present. Distinctive cruciform branched [[hypha]]e develop on infected root tissue which are observable with [[compound microscope]] (Figure 1). In addition, taproots of the infect plant are covered in mycelial strands.<ref>{{Cite journal|last1=Marek|first1=S.M.|last2=Hansen|first2=K.|last3=Romanish|first3=M.|last4=Thorn|first4=R.G.|date=2016-12-08|title=Molecular systematics of the cotton root rot pathogen, ''Phymatotrichopsis omnivora''|journal=Persoonia|volume=22|pages=63–74|doi=10.3767/003158509X430930|issn=0031-5850|pmc=2789547|pmid=20198139}}</ref>
[[File:Cuciform Hyphae of P. Omnivera.jpg|thumb|Figure 1: Cruciform hyphae is a unique sign observable using a [[compound microscope]]]]
Another macroscopic sign is tan and white spore mats developed on the soil surface near the infected plants during favorable high moisture environmental conditions.<ref name=":0" /> Despite the name, these spore mats are not known to aid in dispersal. Although presence of the [[conidia]]l phase on the spore mats is known, the function of the conidia remains unknown since conidial germination is rarely observed.<ref name=":1" />

== Environment ==
The highest concentrations of Texas root rot disease are found in the southwestern United States and northern Mexico, with cases also reported in [[India]] and [[Pakistan]].<ref name=":6">{{Cite journal|last=Percy|first=R.G.|date=1983|title=Potential range of ''Phymatotrichum omnivorum'' as determined by edaphic factors|journal=Plant Disease|volume=67|issue=9|pages=981–983|doi=10.1094/PD-67-981}}</ref> Texas root rot is caused by a pathogen that prefers [[alkali]]ne and [[calcareous]] soils (pH between 7-8.5), affording the potential for control via soil amendment.<ref name=":7">{{Cite journal|last=Uppalapati|first=Srinivasa|date=2010|title=Phymatotrichum (cotton) root rot caused by ''Phymatotrichopsis omnivora'': retrospects and prospects|journal= [[Molecular Plant Pathology]] |volume=11|issue=3|pages=325–334|doi=10.1111/j.1364-3703.2010.00616.x|pmid=20447281|pmc=6640249}}</ref> Scientific research has discovered that both high precipitation and high temperatures (below {{convert|93|F}}) are further environmental enhancers for Texas root rot by increasing its [[virulence]].

The pathogen earned its common name because of the geographical area where it is most prevalent, the cotton-growing region of [[Texas]].<ref name=":7" /> Texas, an area located in the southern half of the [[United States]], receives an annual rainfall between {{convert|127|cm|in|0}} and less than {{convert|25|cm|in|0}}.<ref name=":6" /> Researchers collected data on Texas root rot virulence over 13 years at the [[Blackland Research center|Blackland Research Center]] using cotton plants infected with Texas root rot and found that virulence correlates somewhat with precipitation in the range of {{convert|36|-|100|cm|in|0}} of rainfall.<ref name=":8">{{Cite journal|last=Jeger|first=MJ|date=1986|title=Epidemics of Phymatotrichum root rot (''Phymatotrichum omnivorum'') in cotton: environmental correlates of final incidence and forecasting criteria|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1744-7348.1986.tb03209.x|journal= [[Annals of Applied Biology]] |volume=109|issue=3|pages=325–334|doi=10.1111/j.1744-7348.1986.tb03209.x|url-access=subscription}}</ref> Higher virulence of Texas root rot was observed after large precipitation events.<ref name=":8" /> These experimental findings support the conclusion that Texas root rot preferentially develops in wet over dry soil conditions.<ref name=":8" /> The same study also found that virulence of Texas root rot develops inversely to air temperatures over 93 degrees Fahrenheit.<ref name=":8" />

The symptoms of Texas root rot are most severe during hot summers when air temperature increases the average soil temperature over {{convert|80|F}}. The [[elevation]] in temperatures produces Texas root rot's most severe symptoms: [[wilting]] and bronze colored leaves.<ref name=":9">{{Cite web|last=Goldberg|first=Natalie|date=2018|title=Phymatotrichum root rot|url=https://aces.nmsu.edu/ces/plantclinic/documents/pymatotrichum-root-rot-_od-8__final.pdf|access-date=9 December 2020|website= [[New Mexico State University]] }}</ref> The pathogen is only active in the summer months when the high average temperatures can heat the soil microclimate one foot deep over {{convert|80|F}}.<ref name=":9" />

TRR is a pathogen of [[phytosanitary quarantine|quarantine]] concern for [[Ukraine]].<ref name = "Ukraine" >
{{ Cite journal
 | last1 = Fedorenko | first1 = Vitaliy
 | last2 = Pylypenko | first2 = Liliya
 | title = Kwarantannowe i inwazyjne gatunki występujące na Ukrainie
 | trans-title = Quarantine and invasive species in Ukraine
 | date = 2012
 | publisher = [[Institute of Plant Protection]]
 | journal = [[Progress in Plant Protection]]
 | volume = 52 |issue=4 | pages = 1156–1164
 | issn = 2084-4883
 | s2cid = 130106654
}}
This review is cited by Sladonja ''et al.'', 2015, etc.
</ref>

== Disease cycle ==
[[File:Disease Lifecycle of P. Omnivera.jpg|thumb|Figure 2: disease cycle]]
The disease overwinters as sclerotia or as mycelium on dead plant tissue. In spring to early summer, the germination phase begins with hyphae growth and  root colonization. In middle and late summer, the disease reaches its infectious stage when associated symptoms are observed.<ref name=":1">{{Cite journal|last=UPPALAPATI S.R, YOUNG, C. A., MAREK, S. M. and MYSORE, K. S|year=2010|title=Phymatotrichum (cotton) root rot caused by ''Phymatotrichopsis omnivora'': retrospects and prospects|journal= [[Molecular Plant Pathology]] |volume=11|issue=3|pages=325–334|doi=10.1111/j.1364-3703.2010.00616.x|pmid=20447281|pmc=6640249}}</ref> The pathogen penetrates the host and colonize plant root tissue causing a root rot. This results in the first symptoms of the disease manifested by chlorotic leaves and eventually wilting.<ref name=":1" /> Root rot disease rings enlarge, and the field can be categorized into three zones based upon plant status: asymptomatic, disease front and survivor.<ref>{{cite journal |title=Digital Imaging to Evaluate Root System Architectural Changes Associated with Soil Biotic Factors|journal= [[Phytobiomes Journal]] |year=2019|publisher=American Phytopathological Society|doi=10.1094/PBIOMES-12-18-0062-R|last1=Mattupalli|first1=Chakradhar|last2=Seethepalli|first2=Anand|last3=York|first3=Larry M.|last4=Young|first4=Carolyn A.|volume=3|issue=2|pages=102–111|doi-access=free}}</ref> The pathogen disseminates by infecting neighboring plants, with infected plant tissue serving as a secondary inoculum and further spreading the disease. In situations of high moisture, conidia are produced on spore mats but their role in dispersal is unknown since conidia rarely germinate.<ref name=":1" />

''P. omnivora'' forms several kinds of differentiated hyphae. Initially, hyphae emerge from [[sclerotia]] overwintering in soil.<ref name=":1" /> Sclerotia are the primary inoculum in affected fields.<ref name=":2" /> The emerging hyphae either infects the host root or form mycelial strands with a differentiated rind. Upon contact with host roots, ''P. omnivora'' forms a mycelial mantle on the root's surface.<ref name=":2" /> This leads to necrosis of epidermis and underlying cortical tissue, leading to root lesions. As the disease progresses, the roots are covered by the characteristic cinnamon-colored mycelial strands covered with acircular sterile hyphae, a diagnostic sign of Texas Root Rot.<ref name=":2" /> The roots at later stages of infection show extensive vascular discoloration due to root necrosis. The mycelial strands and symptom development in field-infected roots are especially conspicuous on cotton.<ref name=":2" /> During the late summer and fall, mycelial strands formed on the root surfaces or in the soil form sclerotia to survive the winter, thus completing the life cycle.

== Pathogenesis ==
As a soil borne pathogen, ''P. omnivora'' enters the plant host via the roots.<ref name=":1" /> It penetrates the host by growing infectious hyphae that cover the host plant root's epidermis and eventually infects epidermis and cortical cell junctions of plant host instead of having specialized penetration organs like an appressoria.<ref name=":1" /> From there the fungal pathogen infects root vascular system and begin cause cortical root lesions, which is most pronounced in cotton. Microarray analysis and gene expression profiling revealed that certain pathways related to plant defense such as jasmonic acid, ethylene, and flavonoid production were reduced at later infectious stages.<ref name=":2">{{Cite journal|last=Uppalapati, S. R. |display-authors=etal |year=2009|title=Global Gene Expression Profiling During ''Medicago truncatula''–''Phymatotrichopsis omnivora'' Interaction Reveals a Role for Jasmonic Acid, Ethylene, and the Flavonoid Pathway in Disease Development|journal= [[Molecular Plant-Microbe Interactions]] |volume=22|issue=1|pages=7–17|doi=10.1094/mpmi-22-1-0007|pmid=19061398|doi-access=free}}</ref> This suggests that ''P. omnivora'' is able to suppress the production of these phytochemical defenses to ensure disease success.<ref name=":2" />

== Control ==
The most common management strategy to limit the spread and damage produced by Texas root rot is soil manipulation. The goal of soil manipulation is to create a soil environment that is not favorable to Texas root rot to limit its activity. A common approach is to change the soil acidity/soil [[pH]] because the pathogen prefers alkaline soils. A recommended method to decrease soil pH is through the application of [[ammonium sulfate]] or [[ammonium phosphate]] fertilizer  at around {{cvt|4.5|kg|0}} per {{cvt|9.3|m2|0}}. Applications of fertilizer in this manner causes the soil pH to decrease making it less favorable to Texas root rot disease which prefers a more basic soil environment.<ref name=":4">{{Cite web|date=2007-09-27|title=Texas Root Rot, ''Phymatotrichopsis omnivora'' (Duggar) Hennebert [Syn. ''Phymatotrichum omnivorum'' (Shear) Duggar] - Ash Pests: A Guide to Major Insects, Diseases, Air Pollution Injury, and Chemical Injury|url=http://www.forestpests.org/ash/texasroot.html|archive-url=https://web.archive.org/web/20070927045415/http://www.forestpests.org/ash/texasroot.html|url-status=dead|archive-date=2007-09-27|access-date=2020-12-09}}</ref> This management method is impracticable for any moderate or large scale agricultural operation because of the cost required to amend large areas of soil. However, it is well-suited for hobby gardens or other small scale operations.

Texas root displays a varied infection pattern so the most effective treatment plans contain a variety of management strategies. Other control methods for Texas root rot are deep plowing of the soil post-harvest, the establishment of protective plant barriers, and the incorporation of [[Organic matter|organic]] crop residues into the soil.<ref>{{Cite web|title=Cotton Root Rot {{!}} Texas Plant Disease Handbook|url=https://plantdiseasehandbook.tamu.edu/problems-treatments/problems-affecting-multiple-crops/cotton-root-rot/|access-date=2020-12-09|website=plantdiseasehandbook.tamu.edu}}</ref> Deep plowing after harvest breaks up potentially infected soil {{convert|6 to 10|in|cm|0}} deep and has been shown to combat Texas root rot by disrupting the pathogen’s ability to form [[Sclerotium|sclerotia]].

The planting of resistant grass crops, such as [[sorghum]], to surround an already infected area can limit the spread of Texas root rot to other areas. By surrounding susceptible crops with immune grasses, a barrier layer in the soil can be created to block root infection of susceptible crops.<ref name=":0" />

Organic amendments are an effective treatment against Texas root rot when applied to the soil before spring planting. The most effective amendment is composed of residues from [[wheat]], [[oat]]s, and other [[cereal crops]]. Though sources disagree, crop rotation is not an effective control method because of Texas root rot’s wide host range of over 2,000 host species.<ref name=":7" /> Overall, it is best to avoid areas known to suffer from the Texas root rot because no management technique is a guarantee to control the pathogen.

== Importance ==
Texas root rot (''Phymatotrichopsis omnivora'') is regarded as one of the most impactful diseases of woody dicotyledon plants in large part because of its wide array of dicotyledon host plants, featuring one of the largest host ranges of any known fungal pathogen with over 2,000 possible host species.<ref name=":5" /> Though Texas root rot has been studied since 1888, there are few effective management tools because of the unique biological characteristics of the pathogen. Namely, its ability to last virtually indefinitely in soil and its capacity to survive on roots of native vegetation without producing symptoms.<ref name=":9" /> The species' broad host range also makes management difficult because disease populations can be maintained across various host species.

Texas root rot presents a serious economic threat to cotton growers with losses of upwards of $29 million in cotton found in Texas as estimated by Texas A&M.<ref name=":4" />

== References ==
{{Reflist}}

== External links ==
* [http://cals.arizona.edu/pubs/diseases/az1150.html Cotton (Texas) Root Rot]
* [https://web.archive.org/web/20070927045415/http://www.forestpests.org/ash/texasroot.html Texas Root Rot]
* [http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=320424 Index Fungorum - ''Phymatotrichopsis omnivora'']
* [https://web.archive.org/web/20070820101227/http://nt.ars-grin.gov/fungaldatabases/ USDA ARS Fungal Database]
* [https://web.archive.org/web/20070927173912/http://www.eppo.org/QUARANTINE/fungi/Phymatotrichopsis_omnivora/PHMPOM_ds.pdf EPPO Quarantine pest: ''Phymatotrichopsis omnivora'']
* [http://www.persoonia.org/Issue/22/07.pdf Persoonia - Molecular Systematics of ''Phymatotrichopsis omnivora'']
* [http://www.cals.ncsu.edu/course/pp728/Phymatotrichopsis/index.html NC State Pathogen Profile]

{{Taxonbar|from=Q7708288}}


{{DEFAULTSORT:Texas Root Rot}}
[[Category:Pezizales|Phymatotrichopsis]]
[[Category:Fungal plant pathogens and diseases]]
[[Category:Cotton diseases]]