View source for Biology:Phytophthora nicotianae

{{Short description|Species of single-celled organism}}
{{Speciesbox
| image = 
| image_alt = 
| image_caption = 
| genus = Phytophthora
| species = nicotianae
| authority = Breda de Haan, (1896)<ref name=BDH>Breda de Haan, J. van. 1896. De bibitziekte in de Deli-tabak veroorzaakt door Phytophthora nicotianae. Mededeelingen uit 's Lands Plantentuin Batavia. 15: 57 (1896)</ref>
| synonyms = 
*''Blepharospora terrestris'' <small>(Sherb.) Peyronel</small><ref name="gbif">
Phytophthora nicotianae Breda de Haan stdterms.in GBIF Secretariat (2017). GBIF Backbone Taxonomy. Checklist dataset https://doi.org/10.15468/39omei accessed via https://www.gbif.org/species/3203651 on 2018-06-24.
</ref>
*''Phloeophthora nicotianae'' <small>(Breda de Haan) G.W.Wilson</small><ref name="gbif" />
*''Phloeophthora nicotiane'' <small>(Breda de Haan) G.W.Wilson</small><ref name="gbif" />
*''Phytophthora allii'' <small>Sawada</small><ref name="gbif" />
*''Phytophthora formosana'' <small>Sawada</small><ref name="gbif" />
*''Phytophthora imperfecta var. nicotianae'' <small>Breda de Haan</small><ref name="gbif" />
*''Phytophthora imperfecta var. nicotianae'' <small>Breda de Haan ex Sarej.</small><ref name="gbif" />
*''Phytophthora lycopersici'' <small>Sawada</small><ref name="gbif" />
*''Phytophthora manoana'' <small>Sideris</small><ref name="gbif" />
*''Phytophthora melongenae'' <small>Sawada</small><ref name="gbif" />
*''Phytophthora melongenae subsp. ananaphthoros'' <small>Sideris</small><ref name="gbif" />
*''Phytophthora melongenae var. melongenae'' <small>Sawada, 1915</small><ref name="gbif" />
*''Phytophthora nicotianae subsp. parasitica'' <small>(Dastur) G.M.Waterh., 1963</small><ref name="gbif" />
*''Phytophthora nicotianae var. nicotianae'' <small>Breda de Haan, 1896</small><ref name="gbif" />
*''Phytophthora nicotianae var. parasitica'' <small>(Dastur) G.M.Waterh.</small><ref name="gbif" />
*''Phytophthora parasitica'' <small>Dastur</small><ref name="gbif" />
*''Phytophthora parasitica subsp. nicotianae'' <small>(Breda de Haan) Tucker</small><ref name="gbif" />
*''Phytophthora parasitica subsp. rhei'' <small>G.H.Godfrey, 1923</small><ref name="gbif" />
*''Phytophthora parasitica var. nicotianae'' <small>Tucker</small><ref name="gbif" />
*''Phytophthora parasitica var. piperina'' <small>Dastur</small><ref name="gbif" />
*''Phytophthora parasitica var. rhei'' <small>G.H.Godfrey</small><ref name="gbif" />
*''Phytophthora ricini'' <small>Sawada</small><ref name="gbif" />
*''Phytophthora tabaci'' <small>Sawada</small><ref name="gbif" />
*''Phytophthora terrestris'' <small>Sherb.</small><ref name="gbif" />
| subdivision_ranks = Varieties
| subdivision_ref = <ref name=NCBI>{{cite web|author1=<!-- not stated -->|title=''Phytophthora''|url=https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=4783&lvl=3&keep=1&srchmode=1&unlock|website=NCBI taxonomy|publisher=National Center for Biotechnology Information|access-date=18 June 2018|location=Bethesda, MD|language=en}}</ref>
| subdivision = 
*''Phytophthora nicotianae'' var. ''parasitica'' <small></small>
}}

'''''Phytophthora nicotianae''''' or '''black shank''' is an oomycete belonging to the order [[Biology:Peronosporales|Peronosporales]] and family [[Biology:Peronosporaceae|Peronosporaceae]].

==Hosts and symptoms==
''Phytophthora nicotianae'' has a broad host range comprising 255 genera from 90 families.<ref name=":3">{{Cite web|url=http://www.phytophthoradb.org/species.php?a=dv&id=16086&p=1&l=200&sv=&sf=&opt=0|title=''Phytophthora'' Database|website=www.phytophthoradb.org|access-date=2016-12-08}}</ref> Hosts include [[Biology:Tobacco|tobacco]], [[Biology:Onion|onion]], [[Biology:Tomato|tomato]], ornamentals, [[Biology:Cotton|cotton]], pepper, and [[Biology:Citrus|citrus]] plants. This pathogen can cause [[Biology:Root rot|root rot]], crown rot, fruit rot, leaf infection, and stem infection. Root rot symptoms are observed on tobacco, [[Biology:Poinsettia|poinsettia]], tomato, [[Biology:Pineapple|pineapple]], [[Biology:Watermelon|watermelon]], and  as well as [[Biology:Streptocarpus sect. Saintpaulia|African violet]]. Fruit rots occur on tomato, [[Biology:Papaya|papaya]], and [[Biology:Eggplant|eggplant]]. Onion shows a leaf and stem infection. In tobacco black shank affects the roots and basal stem area, but all parts of the plant can become infected.<ref>{{Cite web|url=http://www.extento.hawaii.edu/kbase/crop/type/p_nicoti.htm|title=''Phytophthora nicotianae''|website=www.extento.hawaii.edu|access-date=2016-12-07}}</ref> [[Biology:Damping off|Damping off]] symptoms can be observed in young seedlings. The first above ground symptom that will be observed is the wilting of plants, which leads to stunting. Roots will be blackened and decayed. In final stages of the disease the stem begins to turn black, hence the name black shank. As this happens, tobacco leaves turn brown and become not marketable. Another symptom is disk-like appearance of the [[Biology:Pith|pith]], although this is not a definitive symptom as it may also be the result of [[Astronomy:Lightning|lightning]] strikes.<ref name=":3" /><ref name=":0">{{Cite web|url=https://projects.ncsu.edu/cals/course/pp728/Phytophthora/Ppnicotianae.htm|title=Melinda Sullivan|last=Sullivan|first=Melinda|website=projects.ncsu.edu|access-date=2016-12-07}}</ref> On [[Biology:Allium cepa|onion]] it causes the disease known as ''Phytophthora'' neck and bulb rot. Different stages of onion may be affected. Initially, tips of newly infected plants start to yellow and dry followed by softening of the "neck" of the plants that eventually fall over. Infected leaves may show grey lesions. Roots may become necrotic in late disease.<ref>{{Cite news|url=http://www.seminis-us.com/resources/disease-guides/onions/phytophthora-neck-bulb-rot/|title=''Phytophthora'' Neck And Bulb Rot {{!}} Seminis|newspaper=Seminis|language=en-US|access-date=2016-12-07}}</ref>
[[File:Black Shank on Tobacco at H. Davis farm.jpg|thumb|Black shank affecting a field of tobacco]]

==Disease cycle==
[[File:Black Shank infecting American Boxwoods (Pcinnamomi).jpg|thumb|Black shank infection on American boxwood]]
Black shank is a polycyclic soil borne disease, with the possibility of multiple disease cycles per growing season occurring from May to October. There are important structures this pathogen uses in its disease cycle. [[Biology:Chlamydospore|Chlamydospore]]s are produced asexually and serve as long lived resting structures, surviving from four to six years.<ref name=":1">{{Cite web|url=http://www.apsnet.org/edcenter/intropp/lessons/fungi/oomycetes/Pages/BlackShank.aspx|title=Black shank of tobacco|last=Gallup|first=C. M.|last2=Sullivan|first2=M. J.|website=www.apsnet.org|access-date=2016-12-07}}</ref> Chlamydospores are the primary survival structure, the primary [[Biology:Propagule|inoculum]], and are usually produced in abundance.<ref name=":3" /> These [[Biology:Spore|spore]]s germinate in warm and moist soil to produce a [[Biology:Germ tube|germ tube]] that infects plants or produces a [[Biology:Sporangium|sporangium]]. Another asexual structure and secondary inoculum, appearing ovoid, pear, or spherical in shape are called sporangium. These spores are produced and can either germinate directly or release motile [[Biology:Zoospore|zoospore]]s within 24 hours of inoculation with the right conditions. Zoospores are kidney shaped with an anterior tinsel [[Biology:Flagellum|flagellum]] and a posterior whip like flagellum that helps to navigate toward root tips were infection occurs. Black shank needs water for germination and movement because zoospores swim through soil pores and standing water. Splashing water from rain or irrigation can infect healthy plant leaves leading to more repeating secondary cycles.<ref name=":2">{{Cite web|url=https://ag.tennessee.edu/EPP/Extension%20Publications/Plant%20Disease%20Black%20Shank%20of%20Tobacco.pdf|title=Plant Diseases: Black Shank of Tobacco|last=Bost|first=S|last2=Hensley|first2=D.|access-date=2016-12-07}}</ref> Zoospores [[Physics:Chemotaxis|move toward nutrient gradients]] around root tips and host wounds. Once the root surface is contacted, zoospores encyst and a germ tube will emerge penetrating the [[Biology:Epidermis|epidermis]]. Infection leads to systemic rotting of the root system and wilting and chlorosis in the leaves. Another structure called [[Biology:Hypha|hypha]]e is colorless, transparent, and coenocytic, but colonies may yellow with age. Also, there is much morphological variation in colony type with different isolates of ''P. nicotianae'' and the growth may differ when grown on different media. The hyphae are heterothallic and require two [[Biology:Mating type|mating type]]s to produce [[Biology:Oospore|oospore]]s, the sexual survival structure. Many fields only contain one mating type, so the zoospores rarely germinate and rarely cause epidemics.<ref name=":1" />

==Environment==
[[File:Black Shank on Tobacco Stem.jpg|thumb|Discing of tobacco pith]]
[[File:Black Shank Disease Cycle.jpg|thumb|372x372px|''Phytophthora nicotianae'' disease cycle]]
This pathogen thrives in temperatures ranging from {{convert|84-90|°F}}. Disease is prominent in many agricultural productive regions and therefore is a major host to many warm environment crops.<ref name=":1" /> Black shank needs water for germination and movement. Saturated soil optimizes disease spread because water is used for dissemination of motile zoospores and sporangia. Low-lying areas of the soil that remain wet for prolonged periods of time will have more disease. Splashing water from rain or [[Earth:Irrigation|irrigation]] can infect healthy plant leaves leading to more repeating secondary cycles. Soils that are not saturated will lead to little to no disease development, so water management is important. Optimum soil [[Chemistry:PH|pH]] for development is between 6 and 7. Levels of [[Chemistry:Calcium|calcium]] and [[Chemistry:Magnesium|magnesium]] in the soils can affect disease progress.<ref name=":0" />

==Management==
Several kinds of management exist for the prevention and suppression of disease. A cultural method that can be effective in preventing disease is sanitation. Equipment should be cleaned after use in infested fields so the disease does not spread into uninfested fields. To disrupt chlamydospore germination crops should be grown in drained disease free soil. Also, avoid transplanting without thorough knowledge of the transplant. To limit spread of structures limit traffic in infected fields and always clean after exposure. Disease is favored by pH values greater than 6.2, so lowering the pH is an effective method for preventing germination. pH management can be difficult because tobacco cannot survive in very low pH soils. Soil pH 5.5 to 6 allow successful growth of tobacco and control of disease.<ref name=":1" />

The cultural control, [[Earth:Crop rotation|crop rotation]], is very effective at limiting disease. The longer an infected field is planted in a crop other than the initial infected crop, the lower the population will become. A minimum three-year rotation is recommended. Crop rotation is recommended in combination with resistant varieties as genetic controls. Burley tobacco, burley tobacco hybrids, and dark tobacco are varieties of tobacco that are resistant to black shank. Resistance however is not reliable because a single variety has resistance to only a few races of black shank. Finding new lines of resistance is becoming increasingly important due to new discovered resistant races of the pathogen.

Chemical control is most successful if used with resistant varieties. [[Chemistry:Metalaxyl|Metalaxyl]] or mefenoxam are chemistries used to control ''Phytophthora nicotianae''. Ridomil Gold is an example a systemic pesticide with a metalaxyl chemistry.<ref name=":2" /> Mefenoxam is twice as active as metalaxyl, but they both have the same mode of action. Successful chemical control is difficult because we are limited to these two chemistries that are basically identical. A study by A. S. Csinos and P. F. Bertrand found out at a rate of 3.36&nbsp;kg/ha would not inhibit many of the common races used in their study. Overall, from their study they observed that black shank severity was increasing in Georgia due to metalaxyl sensitivity and resistant races of black shank.<ref>{{Cite journal|last=Csinos|first=A. S.|last2=Bertrand|first2=P. F.|year=1994|title=Distribution of ''Phytophthora parasitica'' var. ''nicotianae'' Races and Their Sensitivity to Metalaxyl in Georgia|url=http://www.apsnet.org/publications/PlantDisease/BackIssues/Documents/1994Articles/PlantDisease78n05_471.PDF|journal=Plant Disease|volume=78|issue=5|pages=471|doi=10.1094/pd-78-0471}}</ref>

==Importance==
''Phytophthora nicotianae'' has a wide host range, affecting agriculture rich areas all over the world. In the {{wipe|United States}} this is a major pathogen of ornamentals, tobacco, and tomato. Black shank is one of the most damaging and far reaching diseases of tobacco. In 1896, black shank was first described in Indonesia by Van Breda de Haan.<ref name=":1" /> Disease was observed near Georgia in 1915 and reached major tobacco growing areas of Kentucky and North Carolina in the 1930s and 1940s. In North Carolina black shank can be found in every county that grows flue-cured tobacco and currently causes statewide losses of 1 to 2.5 percent per year.<ref>{{Cite web|url=https://www.ces.ncsu.edu/depts/pp/notes/Tobacco/tdin004/tdin004.htm|title=Black Shank|website=www.ces.ncsu.edu|access-date=2016-12-07}}</ref> This pathogen thrives in warm climates, so it is destructive on crops grown in these areas. During favorable conditions, new generations of spores can be produced every 72 hours, so if this disease is not managed well it can be very destructive. Susceptible [[Biology:Cultivar|cultivar]]s in the right conditions can reach losses of 100 percent, because infected plants do not recover.<ref name=":1" /> Less than one [[Biology:Propagule|propagule]] per gram of soil can lead to an [[Medicine:Epidemic|epidemic]].<ref name=":0" /> 
[[File:Field of Tobacco diseased by Black Shank.jpg|thumb|Black shank disease effects]]

==Pathogenesis==
This pathogen causes secondary cycles of disease by mode of zoospores. Zoospores interact with the host by sensing and moving toward the nutrient gradients near the root tip and wounds of the plant. Without this means of sensing entry points there would be no secondary cycles of disease.<ref name=":1" /> Zoospores, chlamydospores, and sporangia produce a germ tube that directly penetrates the epidermis of the plant. Without this penetration device the pathogen would not be able to infect the plant. The pathogen interferes with transport by infecting the roots. Typically hyphae can be seen in the pith and cause blackening and necrosis.<ref name=":0" /><ref name=":2" /> Infection can proceed rapidly once the pathogen has made an entrance into the plant. Once established, further reproduction of both chlamydospores and sporangia will occur within host tissues, amplifying the spread of disease within the host plant and spreading out into nearby plants. Upon death of the host, the decomposing infected tissues will release the pathogen back into the soil, in the form of chlamydospores and zoospores. A resting spore, the chlamydospores are capable of surviving in the soil for years, but it has been noted that cold winters cause an inhibitory effect on the survival rate. This results in less black shank infections where tobacco is grown in cooler, more northern climates.<ref name=":0" />

The action of ''P. nicotianae'' is amplified by the presence of [[Biology:Root-knot nematode|root-knot nematode]]s, which through their own feeding habits, assist the pathogen in finding an entrance to the host. This pathogen synergy with root-knot nematodes has the ability to overcome much of the resistance of cultivars especially bred for ''P. nicotianae'' resistance.<ref name=":0" />

==References==
{{Reflist}}

{{Taxonbar|from1=Q3018847|from2=Q20686122}}

[[Category:Phytophthora|nicotianae]]

{{Sourceattribution|Phytophthora nicotianae}}