Stem rust
4941350
223996237
2008-07-06T21:38:55Z
Ka Faraq Gatri
6892069
Category:Puccinia
{{Taxobox
| name = ''Puccinia graminis''
| image= Stem rust close up.jpg
| image_width = 250px
| regnum = [[Fungi]]
| phylum = [[Basidiomycota]]
| classis = [[Urediniomycetes]]
| subclassis = [[Incertae sedis]]
| ordo = [[Uredinales]]
| familia = [[Pucciniaceae]]
| genus = ''[[Puccinia]]''
| species = '''''P. graminis'''''
| binomial = ''Puccinia graminis''
| binomial_authority = Pers., (1794)
| synonyms =
''Dicaeoma anthistiriae''<br>
''Puccinia albigensis''<br>
''Puccinia anthistiriae''<br>
''Puccinia brizae-maximae''<br>
''Puccinia cerealis''<br>
''Puccinia elymina''<br>
''Puccinia favargeri''<br>
''Puccinia graminis f. macrospora''<br>
''Puccinia graminis f.sp. avenae''<br>
''Puccinia graminis f.sp. secalis''<br>
''Puccinia graminis f.sp. tritici''<br>
''Puccinia graminis subsp. major''<br>
''Puccinia graminis var. graminis''<br>
''Puccinia graminis var. stakmanii''<br>
''Puccinia graminis var. tritici''<br>
''Puccinia jubata''<br>
''Puccinia linearis''<br>
''Puccinia megalopotamica''<br>
''Puccinia secalis''<br>
''Puccinia vilis''<br>
''Trichobasis linearis''<br>
}}
The '''stem''', '''black''' or '''cereal rusts''' are caused by the [[fungus]] '''''Puccinia graminis''''' and are a significant disease affecting cereal crops. An [[epidemic]] of stem rust on [[wheat]] caused by race '''Ug99''' is currently spreading across [[Africa]], [[Asia]] and most recently into [[Middle East]] and is causing major concern.
==Biology==
There is considerable genetic diversity within the species ''P. graminis'' and several special forms, ''[[forma specialis]]'', which vary in host range have been identified.
* ''Puccinia graminis f. sp. avenae'', [[oat]]
* ''Puccinia graminis f. sp. dactylis''
* ''Puccinia graminis f. sp. lolii''
* ''Puccinia graminis f. sp. poae''
* ''Puccinia graminis f. sp. secalis'', [[rye]], [[barley]]
* ''Puccinia graminis f. sp. tritici'', [[wheat]], [[barley]]
Like other ''[[Puccinia]]'' species, ''P. graminis'' has a complex life cycle featuring [[alternation of generations]], the fungus is also [[heteroecious]] which means that its various life cycle stages require alternate host species. The complete life cycle of ''P. graminis'' requires [[barberry]] as well as a cereal species.
In the spring and summer, stem rust infections on wheat plants produce [[dikaryotic]] urediniospores, which are spread by the wind to nearby wheat plants, where they germinate and infect wheat by penetrating through the [[stomata]]. This [[polycyclic]] [[asexual]] phase can rapidly spread the infection over a wide area. Towards the end of the growing season, the rust converts to producing teliospores, which again contain these two [[haploid]] nuclei of opposite mating types. Before the winter, the [[karyogamy|nucleii fuse]] to form a diploid cell, which remains dormant until the next spring when it undergoes [[meiosis]] to produce four haploid cells known as basidiospores, borne on a structure called a basidium. The basidiospores then undergo a mitotic nuclear division to produce the mature basidiospore which contains two haploid nuclei of the same mating type. Basidiospores cannot infect cereal plants, but are instead, carried in the wind, and infect young leaves of common barberry (''Berberis vulgaris'') or other susceptible ''Berberis'', ''[[Mahonia]]'', or ''[[Mahoberberis]]'' species or cultivars. On barberry, the basidiospore penetrates the leaf epidermis directly, and the resulting infections produce specialized infection structures called pycnia (or spermagonia).
Pycnia (or spermagonia), which result from infection on young barberry leaves by basidiospores, are the sexual stage of the fungus life cycle. When a receptive [[hyphae]] from one pycnium has been fertilized by pycniospores (or spermatia) from a mating type compatible pycnium, its haploid cells become dikaryotic. The fertilized hyphae forms an aecium, on the underside of the barberry leaf, which produces chains of aeciospores surrounded by a bell-like enclosure of fungal cells. Like the urediniospores and like the cells of the aecium, each aeciospore contains [[dikaryotic|two nuclei]]. Aeciospores are carried by the wind, and infect wheat by penetrating through [[stomata]]. After infecting a wheat plant, the aecispores develop and form uredia under the [[epidermis (botany)|plants epidermis]], these produce the [[dikaryotic]] urediniospores. These uredia eventually rupture the plants epidermis and again spread by the wind to nearby wheat plants, continuing the lifecycle.
[[Image:Puccina graminis lifecycle.gif|left|thumb|Life cycle of ''Puccinia graminis'']]
==Pathology==
The stem rust fungus attacks the aboveground parts of the plant, infected plant produce fewer tillers and set fewer seed. In the case of extremely bad infection the plant may die. The site of infection is a visible symptom of the disease. Where infection has occurred on the stem or leaf, elliptical blisters or pustules called uredia develop
Pycnia typically form on the upper side of barberry leaves, and aecia form within 5-7 days after fertilization on the lower side of the leaf directly below each fertilized pycnium.
==Ug99==
'''Ug99''', which has the designation of '''TTKS''', is a [[Race (biology)|race]] of [[Stem rust|black stem rust]] ''(Puccinia graminis tritici)''.<ref name=Singh>{{cite journal |
url= http://www.ars.usda.gov/SP2UserFiles/ad_hoc/36400500Publications/YJ/PAV054.pdf |
journal = CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources
| title=Current status, likely migration and strategies to mitigate the threat to wheat production from race Ug99 (TTKS) of stem rust pathogen
| year= 2006 |volume=1|issue= No. 054
| author= Singh, RP ''et al''
| doi-doi = 10.1079/PAVSNNR20061054 |accessdate= 2007-04-19
| doi=10.1079/PAVSNNR20061054}} – Review Article</ref>
It is [[Virulence|virulent]] to the great majority of [[wheat]] varieties.<ref name = NewSci> {{cite journal | url = http://environment.newscientist.com/channel/earth/mg19425983.700-billions-at-risk-from-wheat-superblight.html
|journal = New Scientist Magazine |title=Billions at risk from wheat super-blight |year=2007-04-03
|accessdate = 2007-04-19 |issue=issue 2598 |pages = 6–7}}</ref>
The blight was first noted in [[Uganda]] in [[1999]] and has spread throughout the highlands of [[East Africa]]. In January of [[2007]], [[spore]]s blew across to [[Yemen]], and north into [[Sudan]]. In March 2007, [[FAO]] announced its concern regarding the spread through [[Iran]] based on Iranian authorities report.<ref>[http://www.un.org/apps/news/story.asp?NewsID=25859&Cr=cereal&Cr1= Dangerous wheat-killing fungus detected in Iran] from UN News Centre</ref>
==See also==
*[[List of wheat diseases]]
==References==
<references/>
*Schumann, G.L. and K.J. Leonard. 2000. [http://www.apsnet.org/education/LessonsPlantPath/StemRustWheat/top.htm Stem rust of wheat (black rust)]. The Plant Health Instructor. DOI: 10.1094/PHI-I-2000-0721-01
*Leonard, K.J. ''[http://www.ars.usda.gov/Main/docs.htm?docid=10755 Black stem rust biology and threat to wheat growers]'', USDA ARS
*[http://www.speciesfungorum.org/Names/Names.asp Index Fungorum]
*[http://nt.ars-grin.gov/fungaldatabases USDA ARS Fungal Database]
[[Category:Cereal diseases]]
[[Category:Wheat diseases]]
[[Category:Plant pathogens and diseases]]
[[Category:Puccinia]]
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