Magnaporthe grisea

{{Short description|Blast, fungal disease of rice & wheat}} {{Speciesbox | image = Magnaporthe grisea.jpg | image_caption = Conidium and conidiogenous cell | genus = Magnaporthe | species = grisea | authority = (T.T. Hebert) M.E. Barr | synonyms = ''Ceratosphaeria grisea'' T.T. Hebert, (1971) ''Dactylaria grisea'' (Cooke) Shirai, (1910) ''Dactylaria oryzae'' (Cavara) Sawada, (1917) ''Magnaporthe oryzae'' ''Phragmoporthe grisea'' (T.T. Hebert) M. Monod, (1983) ''Pyricularia grisea'' Sacc., (1880) '''(anamorph)''' ''Pyricularia grisea'' (Cooke) Sacc., (1880) ''Pyricularia oryzae'' Cavara, (1891) ''Trichothecium griseum'' Cooke, ''Trichothecium griseum'' Speg., (1882) }}

'''''Magnaporthe grisea''''', also known as '''rice blast fungus''', '''rice rotten neck''', '''rice seedling blight''',''' blast of rice''', '''oval leaf spot of graminea''', '''pitting disease''', '''ryegrass blast''', '''Johnson spot''',<ref name="Serial-Killer" /><ref>Zeigler, RS; Leong, SA; Teeng, PS (1994). "Rice Blast Disease." Wallingford, UK: CABI Centre for Agriculture and Bioscience International.</ref><ref>{{Cite journal | pmid = 19219052 | year = 2009 | last1 = Wilson | first1 = R. A. | title = Under pressure: Investigating the biology of plant infection by ''Magnaporthe oryzae'' | journal = Nature Reviews Microbiology | volume = 7 | issue = 3 | pages = 185–95 | last2 = Talbot | first2 = N. J. | author-link2 = Nick Talbot | doi = 10.1038/nrmicro2032 | s2cid = 42684382 }}</ref><ref>{{Cite journal | doi = 10.1038/nature02880| pmid = 15457264| title = The rice leaf blast pathogen undergoes developmental processes typical of root-infecting fungi| journal = Nature| volume = 431| issue = 7008| pages = 582–6| year = 2004| last1 = Sesma | first1 = A. | last2 = Osbourn | first2 = A. E.| bibcode = 2004Natur.431..582S| s2cid = 549194|author-link2=Anne Osbourn }}</ref><ref>{{Cite journal | pmid = 15846337 | year = 2005 | last1 = Dean | first1 = R. A. | title = The genome sequence of the rice blast fungus ''Magnaporthe grisea'' | journal =Nature | volume = 434 | issue = 7036 | pages = 980–6 | last2 = Talbot | first2 = N. J. | author-link2 = Nick Talbot | last3 = Ebbole | first3 = D. J. | last4 = Farman | first4 = M. L. | last5 = Mitchell | first5 = T. K. | last6 = Orbach | first6 = M. J. | last7 = Thon | first7 = M | last8 = Kulkarni | first8 = R | last9 = Xu | first9 = J. R. | last10 = Pan | first10 = H | last11 = Read | first11 = N. D. | last12 = Lee | first12 = Y. H. | last13 = Carbone | first13 = I | last14 = Brown | first14 = D | last15 = Oh | first15 = Y. Y. | last16 = Donofrio | first16 = N | last17 = Jeong | first17 = J. S. | last18 = Soanes | first18 = D. M. | last19 = Djonovic | first19 = S | last20 = Kolomiets | first20 = E | last21 = Rehmeyer | first21 = C | last22 = Li | first22 = W | last23 = Harding | first23 = M | last24 = Kim | first24 = S | last25 = Lebrun | first25 = M. H. | last26 = Bohnert | first26 = H | last27 = Coughlan | first27 = S | last28 = Butler | first28 = J | last29 = Calvo | first29 = S | last30 = Ma | first30 = L. J. | display-authors = 29 | doi = 10.1038/nature03449 | bibcode = 2005Natur.434..980D | doi-access = free }}</ref><ref>{{Cite journal | pmid = 21156541 | year = 2002 | last1 = Couch | first1 = B. C. | title = A multilocus gene genealogy concordant with host preference indicates segregation of a new species, ''Magnaporthe oryzae'', from ''M. grisea'' | journal = Mycologia | volume = 94 | issue = 4 | pages = 683–93 | last2 = Kohn | first2 = L. M. | doi=10.2307/3761719 | jstor = 3761719 }}</ref><ref>[http://www.cabicompendium.org/NamesLists/CPC/Full/PYRIOR.htm ''Magnaporthe grisea''] {{webarchive|url=https://web.archive.org/web/20071012212113/http://www.cabicompendium.org/NamesLists/CPC/Full/PYRIOR.htm |date=2007-10-12 }} at [http://www.cabi.org/compendia/cpc/ Crop Protection Compendium] {{webarchive|url=https://web.archive.org/web/20070716191745/http://www.cabi.org/compendia/cpc/ |date=2007-07-16 }}, CAB International</ref> '''neck blast''',<ref name="TeBeest-2007">{{cite journal | title=Rice Blast | journal=The Plant Health Instructor | publisher=American Phytopathological Society (APS)| year=2007 | issn=1935-9411 | doi=10.1094/phi-i-2007-0313-07 | last1=Te Beest }}</ref><ref name="Khan-et-al-2014">{{cite journal | last1=Khan | first1=Mohammad Ashik Iqbal | last2=Rejwan Bhuiyan | first2=Mohammad | last3=Hossain | first3=Mohammad Shahadat | last4=Pratim Sen | first4=Partha | last5=Ara | first5=Anjuman | last6=Abubakar Siddique | first6=Md | last7=Ansar Ali | first7=Md | title=Neck blast disease influences grain yield and quality traits of aromatic rice | journal=Comptes Rendus Biologies | publisher=Elsevier Masson | volume=337 | issue=11 | year=2014 | issn=1631-0691 | doi=10.1016/j.crvi.2014.08.007 | pages=635–641| pmid=25444707 | url=https://comptes-rendus.academie-sciences.fr/biologies/articles/10.1016/j.crvi.2014.08.007/ | url-access=subscription }}</ref><ref name="Roumen-et-al-1992">{{cite journal | last=Roumen | first=E. C. | title=Partial resistance to neck blast influenced by stage of panicle development and rice genotype | journal=Euphytica | publisher=Springer Science and Business Media LLC | volume=64 | issue=3 | year=1992 | issn=0014-2336 | doi=10.1007/bf00046046 | pages=173–182| s2cid=45126761 }}</ref><ref name="Titone-et-al-2015">{{cite journal | last1=Titone | first1=Patrizia | last2=Mongiano | first2=Gabriele | last3=Tamborini | first3=Luigi | title=Resistance to neck blast caused by ''Pyricularia oryzae'' in Italian rice cultivars | journal=European Journal of Plant Pathology | publisher=Springer Science and Business Media LLC | volume=142 | issue=1 | date=2015-01-04 | issn=0929-1873 | doi=10.1007/s10658-014-0588-1 | pages=49–59| s2cid=14478689 | doi-access=free | bibcode=2015EJPP..142...49T }}</ref> '''wheat blast'''<ref name="Kumar" /> and {{nihongo||稲熱|'''Imochi'''}}, is a plant-pathogenic fungus and model organism<ref name="Yarden-et-al-2003" /> that causes a serious disease affecting rice. It is now known that ''M. grisea'' consists of a cryptic species complex containing at least two biological species that have clear genetic differences and do not interbreed.<ref name="Couch-et-al-2005">{{Cite journal | pmid = 15802503 | pmc = 1450392 | year = 2005 | last1 = Couch | first1 = B. C. | title = Origins of host-specific populations of the blast pathogen ''Magnaporthe oryzae'' in crop domestication with subsequent expansion of pandemic clones on rice and weeds of rice | journal =Genetics | volume = 170 | issue = 2 | pages = 613–30 | last2 = Fudal | first2 = I | last3 = Lebrun | first3 = M. H. | last4 = Tharreau | first4 = D | last5 = Valent | first5 = B | last6 = Van Kim | first6 = P | last7 = Nottéghem | first7 = J. L. | last8 = Kohn | first8 = L. M. | doi = 10.1534/genetics.105.041780 }}</ref> Complex members isolated from ''Digitaria'' have been more narrowly defined as ''M. grisea''. The remaining members of the complex isolated from rice and a variety of other hosts have been renamed '''''Magnaporthe oryzae''''', within the same ''M. grisea'' complex.<ref name="Couch-et-al-2005" /> Confusion on which of these two names to use for the rice blast pathogen remains, as both are now used by different authors.

Members of the ''M. grisea'' complex can also infect other agriculturally important cereals including wheat, rye, barley, and pearl millet causing diseases called '''blast disease''' or '''blight disease'''. Rice blast causes economically significant crop losses annually. Each year it is estimated to destroy enough rice to feed more than 60 million people. The fungus is known to occur in 85 countries worldwide<ref name="California" /> and {{as of|2003|lc=yes}} was the most devastating fungal plant pathogen in the world.<ref name="Yarden-et-al-2003" />

== Hosts and symptoms ==

''M. grisea'' is an ascomycete fungus. It is an extremely effective plant pathogen as it can reproduce both sexually and asexually to produce specialized infectious structures, appressoria, that infect aerial tissues and hyphae that can infect root tissues.

Rice blast has been observed on rice strains M-201, M-202, M-204, M-205, M-103, M-104, S-102, L-204, Calmochi-101, with M-201 being the most vulnerable.<ref>[http://www.ipm.ucdavis.edu/PMG/r682100611.html Rice Blast] at University of California Integrated Pest Management (UC-IPM)</ref> Initial symptoms are white to gray-green lesions or spots with darker borders produced on all parts of the shoot, while older lesions are elliptical or spindle-shaped and whitish to gray with necrotic borders. Lesions may enlarge and coalesce to kill the entire leaf. Symptoms are observed on all above-ground parts of the plant.<ref>[http://www.oisat.org/pests/diseases/fungal/rice_blast.html Rice Blast] at the Online Information Service for Non-Chemical Pest Management in the Tropics</ref> Lesions can be seen on the leaf collar, culm, culm nodes, and panicle neck node. Internodal infection of the culm occurs in a banded pattern. Nodal infection causes the culm to break at the infected node (rotten neck).<ref>[http://www.cbwinfo.com/Biological/PlantPath/PyG.html Rice Blast] {{webarchive|url=https://web.archive.org/web/20101020063252/http://cbwinfo.com/Biological/PlantPath/PyG.html |date=2010-10-20 }} at Factsheets on Chemical and Biological Warfare Agents</ref> It also affects reproduction by causing the host to produce fewer seeds. This is caused by the disease preventing maturation of the actual grain.<ref name="California" />

== Disease cycle == [[File:Rice blast spores.jpg|thumb|left|195px|Spores]] The pathogen infects as a spore that produces lesions or spots on parts of the rice plant such as the leaf, leaf collar, panicle, culm and culm nodes. Using a structure called an appressorium, the pathogen penetrates the plant. The appressorium cell wall is chitinous and its inner side contains melanin.<ref name="Serial-Killer" />{{ RP | page=184}} which is necessary to damage host structures.<ref name="Serial-Killer" />{{ RP | page=184}} <ref name="Yarden-et-al-2003" /> The turgor pressure generated during this process is sufficient to penetrate the plants' cuticles routinely, and experimentally can penetrate Kevlar. This impressive turgor is produced by synthesis of glycerol and maintained by the aforementioned appressorial melanin.<ref name="Yarden-et-al-2003">{{cite journal | last1=Yarden | first1=O. | last2=Ebbole | first2=D. J. | last3=Freeman | first3=S. | last4=Rodriguez | first4=R. J. | last5=Dickman | first5=M. B. | title=Fungal Biology and Agriculture: Revisiting the Field | journal=Molecular Plant-Microbe Interactions | publisher=American Phytopathological Society (APS)| volume=16 | issue=10 | year=2003 | issn=0894-0282 | doi=10.1094/mpmi.2003.16.10.859 | pages=859–866 | s2cid=20430256 | pmid=14558687| url=https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1345&context=plantpathpapers | url-access=subscription }}</ref> The pathogen is able to move between the plant cells using its invasive hyphae to enter through plasmodesmata.<ref>{{cite journal |last1=Sakulkoo |first1=Wasin |last2=Osés-Ruiz |first2=Miriam |last3=Oliveira Garcia |first3=Ely |last4=Soanes |first4=Darren |last5=Littlejohn |first5=George |last6=Hacker |first6=Christian |last7=Correia |first7=Ana |last8=Valent |first8=Barbara |last9=Talbot |first9=Nicholas |title=A single fungal MAP kinase controls plant cell-to-cell invasion by the rice blast fungus |journal=Science|date=23 Mar 2018 |volume=359 |issue=6382 |pages=1399–1403 |doi=10.1126/science.aaq0892|pmid=29567712 |bibcode=2018Sci...359.1399S |doi-access=free |hdl=10871/32530 |hdl-access=free }}</ref> ''M. grisea'' then sporulates from the diseased rice tissue to be dispersed as conidiospores.<ref name="Agrios">{{cite book |title=Plant Pathology |first= George N. |last=Agrios |publisher=Elsevier Academic Press|location=Amsterdam|year=2005}}</ref> After overwintering in sources such as rice straw and stubble, the cycle repeats.<ref name="California">{{cite web |url=http://www.plantsciences.ucdavis.edu/uccerice/afs/agfs0297.htm |first=S.C.|last=Scardaci|series=Agronomy Fact Sheet Series|issue=1997–2|publisher=University of California-Davis (UCD)|year=2003 |title=Rice Blast: A New Disease in California|archive-url=https://web.archive.org/web/20060911083717/http://www.plantsciences.ucdavis.edu/uccerice/AFS/agfs0297.htm |archive-date=2006-09-11 |access-date=2014-02-25|display-authors=etal}}</ref>

A single cycle can be completed in about a week under favorable conditions where one lesion can generate up to thousands of spores in a single night. Disease lesions, however, can appear in three to four days after infection.<ref>{{cite journal |last1=Wilson |first1=Richard |last2=Talbot |first2=Nicholas |title=Under pressure: investigating the biology of plant infection by ''Magnaporthe oryzae'' |journal=Nature Reviews Microbiology |date=1 Mar 2009 |volume=7 |issue=3 |pages=185–189 |doi=10.1038/nrmicro2032 |pmid=19219052|s2cid=42684382 }}</ref> With the ability to continue to produce the spores for over 20 days, rice blast lesions can be devastating to susceptible rice crops.<ref>[http://www.padil.gov.au/pbt.htm Diagnostic Methods for Rice Blast]{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }} at PaDIL Plant Biosecurity Toolbox</ref>

Infection of rice induces phosphorylation of the light-harvesting complex II protein {{ Visible anchor | LHCB5 }}.<ref name = "Double-Edged-Sword" /> LHCB5 is required for a reactive oxygen species burst produced by the host which provides resistance against this pathogen.<ref name = "Double-Edged-Sword" > {{ Cite journal | language = English | year = 2022 | volume = 289 | issue = 18 | first2 = Zhengguang | first1 = Xinyu | last2 = Zhang | last1 = Liu | publisher = John Wiley & Sons, Inc. (Federation of European Biochemical Societies | journal = The FEBS Journal | pages = 5505–5515 | title = A double-edged sword: reactive oxygen species (ROS) during the rice blast fungus and host interaction | doi = 10.1111/febs.16171 | pmid = 34453409 | s2cid = 237340135 }} </ref>

== Environment == Rice blast is a significant problem in temperate regions and can be found in areas such as irrigated lowland and upland.<ref name="Grain">{{cite web |url=http://www.grain.org/briefings/?id=138 |title=Implications of corporate strategies on rice research in asia |first=Devlin |last=Kuyek |publisher= Grain |year=2000 |access-date=2010-10-20}}</ref> Conditions conducive for rice blast include long periods of free moisture and/or high humidity, because leaf wetness is required for infection.<ref name="Grain" /> Sporulation increases with high relative humidity and at {{convert|77|-|82|F|C|order=flip}}, spore germination, lesion formation, and sporulation are at optimum levels.<ref name="California" />

In terms of control, excessive use of nitrogen fertilization as well as drought stress increase rice susceptibility to the pathogen as the plant is placed in a weakened state and its defenses are low.<ref name="California" /> Flooding and draining fields is normal in rice growing, however leaving a field drained for extended periods also favors infection as that will aerate the soil, converting ammonium to nitrate and thus causing stress to rice crops, as well.<ref name="California" />

== Geographical distribution == Wheat blast was found in the 2017–2018 rainy season in Zambia, in the Mpika district of the Muchinga Province.<ref>{{cite web | url=http://wheat.org/researchers-in-zambia-confirm-wheat-blast-has-made-the-intercontinental-jump-to-africa/ | title=Researchers in Zambia confirm: Wheat blast has made the intercontinental jump to Africa | date=24 September 2020 | access-date=1 October 2020 | archive-date=6 October 2021 | archive-url=https://web.archive.org/web/20211006145037/https://wheat.org/researchers-in-zambia-confirm-wheat-blast-has-made-the-intercontinental-jump-to-africa/ }}</ref><ref>{{cite journal | url= | title=Detection and characterization of fungus (''Magnaporthe oryzae'' pathotype ''Triticum'') causing wheat blast disease on rain-fed grown wheat (''Triticum aestivum'' L.) in Zambia | year=2020 | doi=10.1371/journal.pone.0238724 | last1=Tembo | first1=Batiseba | last2=Mulenga | first2=Rabson M. | last3=Sichilima | first3=Suwilanji | last4=m'Siska | first4=Kenneth K. | last5=Mwale | first5=Moses | last6=Chikoti | first6=Patrick C. | last7=Singh | first7=Pawan K. | last8=He | first8=Xinyao | last9=Pedley | first9=Kerry F. | last10=Peterson | first10=Gary L. | last11=Singh | first11=Ravi P. | last12=Braun | first12=Hans J. | journal=PLoS ONE | publisher=Public Library of Science | volume=15 | issue=9 | article-number=e0238724 | pmid=32956369 | pmc=7505438 | bibcode=2020PLoSO..1538724T | s2cid=221843315| doi-access=free }}</ref>

In February 2016 a devastating wheat epidemic struck Bangladesh.<ref name="Islam-et-al-2016">{{cite journal | last1=Islam | first1=M. Tofazzal | last2=Croll | first2=Daniel | last3=Gladieux | first3=Pierre | last4=Soanes | first4=Darren M. | last5=Persoons | first5=Antoine | last6=Bhattacharjee | first6=Pallab | last7=Hossain | first7=Md. Shaid | last8=Gupta | first8=Dipali Rani | last9=Rahman | first9=Md. Mahbubur | last10=Mahboob | first10=M. Golam | last11=Cook | first11=Nicola | last12=Salam | first12=Moin U. | last13=Surovy | first13=Musrat Zahan | last14=Sancho | first14=Vanessa Bueno | last15=Maciel | first15=João Leodato Nunes | last16=NhaniJúnior | first16=Antonio | last17=Castroagudín | first17=Vanina Lilián | last18=Reges | first18=Juliana T. de Assis | last19=Ceresini | first19=Paulo Cezar | last20=Ravel | first20=Sebastien | last21=Kellner | first21=Ronny | last22=Fournier | first22=Elisabeth | last23=Tharreau | first23=Didier | last24=Lebrun | first24=Marc-Henri | last25=McDonald | first25=Bruce A. | last26=Stitt | first26=Timothy | last27=Swan | first27=Daniel | last28=Talbot | first28=Nicholas J. | last29=Saunders | first29=Diane G. O. | last30=Win | first30=Joe | last31=Kamoun | first31=Sophien | title=Emergence of wheat blast in Bangladesh was caused by a South American lineage of ''Magnaporthe oryzae'' | journal=BMC Biology | publisher=Springer Science and Business Media LLC | volume=14 | issue=1 | date=2016-10-03 | page=84 | issn=1741-7007 | doi=10.1186/s12915-016-0309-7 | pmid=27716181 | pmc=5047043 | doi-access=free }}</ref><ref name="Br-Bngl-warn-infographic" /> Transcriptome analysis showed this to be an ''M. grisea'' lineage most likely from Minas Gerais, São Paulo, Brasília, and Goiás states of Brazil and not from any geographically proximate strains.<ref name="Islam-et-al-2016" /><ref name="Br-Bngl-warn-infographic" /> This successful diagnosis shows the ability of genetic surveillance to untangle the novel biosecurity implications of transcontinental transportation<ref name="Islam-et-al-2016" /><ref name="Br-Bngl-warn-infographic" /> and allows the Brazilian experience to be rapidly applied to the Bangladeshi situation.<ref name="Islam-et-al-2016" /><ref name="Br-Bngl-warn-infographic" /> To that end the government has set up an early warning system to track its spread through the country.<ref name="Br-Bngl-warn-infographic">{{cite web | title=New infographic highlights an early warning system for wheat blast in Bangladesh | website=CGIAR WHEAT | date=2020-07-15 | url=http://wheat.org/new-infographic-highlights-an-early-warning-system-for-wheat-blast-in-bangladesh/ | access-date=2020-12-26 | archive-date=2020-12-01 | archive-url=https://web.archive.org/web/20201201000217/https://wheat.org/new-infographic-highlights-an-early-warning-system-for-wheat-blast-in-bangladesh/ }}</ref>

== Management == [[File:J Sendra with Magnaporthe grisea.jpeg|thumb|250px|J. Sendra rice]] This fungus faces both fungicides and genetic resistance in some types of rice developed by plant breeders. It is able to establish both resistance to those chemical treatments and virulence to crop resistance by genetic change through mutation. In order to most effectively control infection by ''M. grisea'', an integrated management program should be implemented to avoid overuse of a single control method and fight against genetic resistance. For example, eliminating crop residue could reduce the occurrence of overwintering and discourage inoculation in subsequent seasons. Another strategy would be to plant resistant rice varieties that are not as susceptible to infection by ''M. grisea''.<ref name="California" /> Knowledge of the pathogenicity of ''M. grisea'' and its need for free moisture suggest other control strategies such as regulated irrigation and a combination of chemical treatments with different modes of action.<ref name="California" /> Managing the amount of water supplied to the crops limits spore mobility thus dampening the opportunity for infection. Chemical controls such as Carpropamid have been shown to prevent penetration of the appressoria into rice epidermal cells, leaving the grain unaffected.<ref name="Biological Activity of Carpropamid">{{cite web|title=Biological Activity of Carpropamid (KTU 3616): A new fungicide for rice blast disease |first=Yoshio |last=Kurahasi |publisher=Journal of Pesticide Science|year=1997 |url=http://eurekamag.com/research/008/229/biological-activity-carpropamid-ktu-3616-fungicide-rice-blast-disease.php |access-date=2014-02-25}}</ref> Papajani et al. 2015 finds the essential oils of both ''Origanum vulgare'' and ''Rosmarinus officinalis'' to be effective in vitro, and provides treatment thresholds.<ref name="Fourmentin-et-al-2018">{{cite book | editor-last1=Fourmentin | editor-first1=Sophie | editor-last2=Crini | editor-first2=Grégorio | editor-last3=Lichtfouse | editor-first3=Eric | title=Environmental Chemistry for a Sustainable World | publisher=Springer International Publishing | publication-place=Cham, Switzerland| year=2018 | volume=17 | isbn=978-3-319-76161-9 | issn=2213-7114 | doi=10.1007/978-3-319-76162-6 | page=| s2cid=199492358 }}</ref>{{ RP | pages=107–108}}

The wheat blast strain can be diagnosed by sequencing.<ref name="Kumar" />{{ RP | page=45}} Thierry ''et al.'', 2020 presents a set of genetic markers which can be found by polymerase chain reaction (PCR), real-time PCR (RT-PCR), and loop-mediated isothermal amplification (LAMP).<ref name="Kumar" />{{ RP | page=45}} The big advantages of the Thierry markers are that they do not miss isolates lacking the Mot3 sequence, for example {{ Visible anchor |BR0032}}, and its great sensitivity.<ref name="Kumar" />{{ RP | page=45}}

Some innovative biologically imitative fungicides are being developed from small RNAs and short peptides.<ref name="Game-Changing" /> {{ Visible anchor |SNP-D4}} is a short peptide located by an in vitro library screen against the ''M. oryzae'' calmodulin.<ref name="Game-Changing" /> It binds to calmodulin, inhibits conidia formation, and blocks spore germination.<ref name="Game-Changing">{{ Cite journal|year=2021|publisher=Cell Press|journal=Trends in Biotechnology|issn=0167-7799|pages=1–18|first7=Simona|first6=Elena|first5=Bruno|first4=Vincent|first3=Chiara|first2=Paolo|first1=Stefano|last7=Masiero|last6=Baraldi|last5=Mezzetti|last4=Bulone|last3=Mizzotti|last2=Pesaresi|last1=Rosa|title=Game-changing alternatives to conventional fungicides: small RNAs and short peptides|volume=40 |issue=3 |doi=10.1016/j.tibtech.2021.07.003|pmid=34489105 |s2cid=237433001 }}</ref>

== Importance == Rice blast is the most important disease concerning rice crops in the world. Since rice is an important food source for much of the world, its effects have a broad range. It has been found in over 85 countries across the world and reached the United States in 1996. Every year the amount of crops lost to rice blast could feed 60 million people. Although there are some resistant strains of rice, the disease persists wherever rice is grown. The disease has never been eradicated from a region.<ref>[http://www.knowledgebank.irri.org/RiceDoctor/index.php?option=com_content&view=article&id=562&Itemid=2767 Rice Blast] {{webarchive|url=https://web.archive.org/web/20100731163031/http://www.knowledgebank.irri.org/RiceDoctor/index.php?option=com_content&view=article&id=562&Itemid=2767 |date=2010-07-31 }} at Cereal Knowledge Bank</ref>

== Strains == Three strains, ''albino'' (defined by a mutation at the ''ALB1'' locus), ''buff'' (''BUF1''), and ''rosy'' (''RSY1''), have been extensively studied because they are nonpathogenic. This has been found to be due to their inability to synthesize melanin, which is a virulence factor in some fungi.<ref name="Serial-Killer">{{ Cite journal | last=Talbot | first=Nicholas J. | title=On the Trail of a Cereal Killer: Exploring the Biology of ''Magnaporthe grisea'' | journal=Annual Review of Microbiology | publisher=Annual Reviews | volume=57 | issue=1 | year=2003 | issn=0066-4227 | doi=10.1146/annurev.micro.57.030502.090957 | pages=177–202 | pmid=14527276 | author-link=Nick Talbot |quote=Three mutants of ''M. grisea'', ''albino'', ''buff'', and ''rosy'' (corresponding to the ''ALB1'', ''BUF1'', and ''RSY1'' loci, respectively), have been studied extensively and are nonpathogenic. This is due to an inability to cross the plant cuticle because of the lack of melanin deposition in the appressorium. }}</ref>{{ RP | page=184}} The {{ Visible anchor | Wheat Blast | Wheat blast | pv. triticum | Magnaporthe oryzae pathotype Triticum | MoT | Mot | text=pathovar ''triticum'' }} strain (''M. o.'' pv. ''triticum'') causes the '''wheat blast''' disease.<ref name="Kumar">{{cite book | date=2020 | edition=1 | publication-place=Boca Raton, FL, US | publisher=CRC Press | first3=Gyanendra | first2=Prem | first1=Sudheer | last3=Singh | last2=Kashyap | last1=Kumar | oclc=1150902336 | doi=10.1201/9780429470554 | isbn=978-0-429-47055-4 | title=Wheat Blast| s2cid=235049332 }}</ref> Export of Magnaporthe from the US is restricted.<ref>{{Cite web |title=Supplement No. 1 to Part 774—The Commerce Control List {{!}} Bureau of Industry and Security |url=https://www.bis.gov/ear/title-15/subtitle-b/chapter-vii/subchapter-c/part-774/supplement-no-1-part-774-commerce-control#1C354 |access-date=2024-08-14 |website=www.bis.gov}}</ref>

== Genetics ==

Whole-genome sequences were just becoming possible, and being made available, in 2003.<ref name="Yarden-et-al-2003" />

A mitogen-activated protein kinase (MAPK) called ''pmk1'' is genetically close to one necessary for mating and cell morphology in yeasts, ''FUS3''/''KSS1''. Defective mutant yeast are somewhat or entirely restored in mating function if they are given a copy of ''pmk1''. It was therefore assumed that this must only be a mating and development gene in ''M. grisea'', however it turns out to be both vital to the female mating process and in appressorium function and pathogenicity as a whole.<ref name="Yarden-et-al-2003" />

Because signal links between MAPKs and cyclic adenosine monophosphates were shown to be required for mating in several other models, including ''Ustilago maydis'' and several others, this was assumed to be true for ''M. grisea'', and yet that was then shown to be unnecessary in this model. This demonstrates significant variety in cellular function within fungi.<ref name="Yarden-et-al-2003" />

The transaminase alanine: glyoxylate aminotransferase 1 (AGT1) has been shown to be crucial to the pathogenicity of ''M. grisea'' through its maintenance of redox homeostasis in peroxisomes. Lipids transported to the appressoria during host penetration are degraded within a large central vacuole, a process that produces fatty acids. β-Oxidation of fatty acids is an energy producing process that generates Acetyl-CoA and the reduced molecules FADH2 and NADH, which must be oxidized in order to maintain redox homeostasis in appressoria. AGT1 promotes lactate fermentation, oxidizing NADH/FADH2 in the process.<ref>{{Cite journal |last1=Bhadauria |first1=Vijai |last2=Banniza |first2=Sabine |last3=Vandenberg |first3=Albert |last4=Selvaraj |first4=Gopalan |last5=Wei |first5=Yangdou |date=2012-04-27 |title=Peroxisomal Alanine: Glyoxylate Aminotransferase AGT1 Is Indispensable for Appressorium Function of the Rice Blast Pathogen, ''Magnaporthe oryzae'' |journal=PLOS ONE|language=en |volume=7 |issue=4 |article-number=e36266 |doi=10.1371/journal.pone.0036266 |issn=1932-6203 |pmc=3338719 |pmid=22558413|bibcode=2012PLoSO...736266B |doi-access=free }}</ref>

''M. grisea'' mutants lacking the AGT1 gene were observed to be nonpathogenic through their inability to penetrate host surface membranes. This indicates the possibility of impaired lipid utilization in ''M. grisea'' appressoria in the absence of the AGT1 gene.<ref name=":0">{{Cite journal |last1=Bhadauria |first1=Vijai |last2=Banniza |first2=Sabine |last3=Vandenberg |first3=Albert |last4=Selvaraj |first4=Gopalan |last5=Wei |first5=Yangdou |date=2012-09-01 |title=Alanine |journal=Plant Signaling & Behavior|volume=7 |issue=9 |pages=1206–1208 |doi=10.4161/psb.21368 |pmc=3489663 |pmid=22899049|bibcode=2012PlSiB...7.1206B }}</ref>

== Biochemistry of host-pathogen interactions ==

A 2010 review reported clones for quantitative disease resistance in plants.<ref name="QDR-QRL-breed">{{ Cite journal |last=St.Clair |first=Dina |year=2010 |title=Quantitative Disease Resistance and Quantitative Resistance Loci in Breeding |journal=Annual Review of Phytopathology |volume=48 |issue=1 |pages=247–268 |doi=10.1146/annurev-phyto-080508-081904 |pmid=19400646 |bibcode=2010AnRvP..48..247S |issn=0066-4286 }}</ref> The rice plant responds to the blast pathogen by releasing jasmonic acid, which cascades into the activation of further downstream metabolic pathways which produce the defense response.<ref name="Secondary-Metabolites"/> This accumulates as methyl-jasmonic acid.<ref name="Secondary-Metabolites" /> The pathogen responds by synthesizing an oxidizing enzyme which prevents this accumulation and its resulting alarm signal.<ref name="Secondary-Metabolites" >{{Cite journal |doi=10.1093/jimb/kuab058 |pmid=34379774 |pmc=8788799 |title=Biosynthesis and biological function of secondary metabolites of the rice blast fungus ''Pyricularia oryzae'' |year=2021 |last1=Motoyama |first1=Takayuki |last2=Yun |first2=Choong-Soo |last3=Osada |first3=Hiroyuki |journal=Journal of Industrial Microbiology and Biotechnology |volume=48 |issue=9–10 }}</ref> {{ Visible anchor |OsPii-2|Pii-2|text=''Os''Pii-2}} is a rice protein that acts as an immunoreceptor.<ref name="Show-Me-Your-ID"/> It binds to the rice's own {{ Visible anchor |Exo70-F3}} protein.<ref name="Show-Me-Your-ID" /> This protein is a target of the ''M. oryzae'' effector {{ Visible anchor |AVR-Pii}} that the fungus secretes during infection. Thus, this allows the ''Os''Pii-2 protein to monitor for ''M. oryzae''{{'}}s attack against that target.<ref name="Show-Me-Your-ID">{{Cite journal |doi=10.1042/ebc20210084 |title=Show me your ID: NLR immune receptors with integrated domains in plants |year=2022 |last1=Marchal |first1=Clemence |last2=Michalopoulou |first2=Vassiliki A. |last3=Zou |first3=Zhou |last4=Cevik |first4=Volkan |last5=Sarris |first5=Panagiotis F. |journal=Essays in Biochemistry |volume=66 |issue=5 |pages=527–539 |pmid=35635051 |pmc=9528084 }}</ref> Some rice cultivars carry resistance alleles of the ''OsSWEET13'' gene, which produces the molecular target of the ''X. oryzae'' pv. ''oryzae'' effector ''PthXo2''.<ref name=PthXo2>{{Cite journal |doi=10.1111/tpj.12838 |s2cid=29633821 |pmid=25824104 |title=Gene targeting by the TAL effector PthXo2 reveals cryptic resistance gene for bacterial blight of rice |year=2015 |last1=Zhou |first1=Junhui |last2=Peng |first2=Zhao |last3=Long |first3=Juying |last4=Sosso |first4=Davide |last5=Liu |first5=Bo |last6=Eom |first6=Joon-Seob |last7=Huang |first7=Sheng |last8=Liu |first8=Sanzhen |last9=Vera Cruz |first9=Casiana |last10=Frommer |first10=Wolf B. |last11=White |first11=Frank F. |last12=Yang |first12=Bing |display-authors=3 |journal=The Plant Journal |volume=82 |issue=4 |pages=632–643 |doi-access=free }}</ref>

== See also == *Corn grey leaf spot, a similar disease in maize/corn *Gray leaf spot, a similar disease in other grasses

== References == {{ Reflist }}

== Further reading == * California EPA. [http://www.arb.ca.gov/newsrel/nr021198.htm Rice Crop Infestation in Three Counties Leads To Emergency Burn Agreement] {{Webarchive|url=https://web.archive.org/web/20181215224308/https://www.arb.ca.gov/newsrel/nr021198.htm |date=2018-12-15 }}, February 11, 1998 * CIMMYT. [https://www.cimmyt.org/news/what-is-wheat-blast/ What is wheat blast?], 2019. * Kadlec, RP. [https://web.archive.org/web/20100106135457/http://www.airpower.maxwell.af.mil/airchronicles/battle/chp10.html Biological Weapons for Waging Economic Warfare], ''Air & Space Power Chronicles'' * NSF. [https://www.nsf.gov/news/news_summ.jsp?cntn_id=104086&org=OLPA&from=news Microbial Genome Helps Blast Devastating Rice Disease] {{Webarchive|url=https://web.archive.org/web/20181215221903/https://www.nsf.gov/news/news_summ.jsp?cntn_id=104086&org=OLPA&from=news |date=2018-12-15 }}, April 21, 2005 * United States Congress. [https://web.archive.org/web/20050501191145/http://www.house.gov/hasc/testimony/106thcongress/99-10-20alibek.htm Testimony of Dr. Kenneth Alibek], 1999 * {{cite web | title=What is wheat blast? | website=CIMMYT | date=2019-12-11 | url=http://www.cimmyt.org/news/what-is-wheat-blast/ | access-date=2020-12-21}} * {{cite web|url=http://repository.cimmyt.org/bitstream/handle/10883/19942/60052.pdf?sequence=1&isAllowed=y|title=What is wheat blast? How can I manage it?|website=CIMMYT}} * {{cite journal | first1=肇 Hajime | last1=加藤 Katō | first2=富夫 Tomio | last2=山口 Yamaguchi | first3=夏樹 Natsuki | last3=西原 Nishihara | title=The perfect state of ''Pyricularia oryzae'' Cav. in culture. | journal=Japanese Journal of Phytopathology | publisher=The Phytopathological Society of Japan | volume=42 | issue=4 | year=1976 | issn=1882-0484 | doi=10.3186/jjphytopath.42.507 | pages=507–510| doi-access=free }} * {{cite web | title=Blast (node and neck) | website=Rice Knowledge Bank | publisher=IRRI (International Rice Research Institute) | date=2017-08-15 | url=http://www.knowledgebank.irri.org/training/fact-sheets/pest-management/diseases/item/blast-node-neck | access-date=2021-03-04}}

== External links == {{Commons category|Magnaporthe oryzae}} * [http://gromo.msubiotech.ac.in/Gromo/Home/ GROMO - Genomic Resources of ''Magnaporthe oryzae'']{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }} * [http://www.broad.mit.edu/annotation/genome/magnaporthe_grisea/ ''Magnaporthe grisea'' Genome] * [https://web.archive.org/web/20090901131850/http://www.riceblast.org/ The official Website of the International Rice Blast Genome Consortium] * [http://www.speciesfungorum.org/Names/Names.asp Index Fungorum] * [https://web.archive.org/web/20090417091347/http://www.metapathogen.com/magnaporthe/ ''Magnaporthe grisea'' at MetaPathogen: stages, tissues, mating types, strains, references]

{{DEFAULTSORT:Magnaporthe Grisea}} Category:Magnaporthales Category:Biological agents Category:Fungal plant pathogens and diseases Category:Rice diseases Category:Fungi described in 1880 Category:Biological anti-agriculture weapons Category:Wheat diseases Category:Fungal models Category:Fungus species