Editing Banana (section)

== Diseases ==

{{main|List of banana and plantain diseases}}

Although in no danger of outright extinction, bananas of the Cavendish group, which dominate the global market, are under threat.<ref name="NewScientist-2006"/> There is a need to enrich banana [[biodiversity]] by producing diverse new banana varieties, not just focusing on the Cavendish.<ref name="Karp-2019"/> Its predecessor '[[Gros Michel]]', discovered in the 1820s, was similarly dominant but had to be replaced after widespread infections of Panama disease. [[Monocropping]] of Cavendish similarly leaves it susceptible to disease and so threatens both commercial cultivation and small-scale subsistence farming.<ref name="NewScientist-2006">{{cite magazine |title=A future with no bananas? |magazine=[[New Scientist]] |date=May 13, 2006 |url=https://www.newscientist.com/channel/earth/dn9152-a-future-with-no-bananas.html |access-date=December 9, 2006 |archive-date=January 18, 2021 |archive-url=https://web.archive.org/web/20210118200955/https://www.newscientist.com/article/dn9152-a-future-with-no-bananas/?ignored=irrelevant |url-status=live }}</ref><ref name="Montpellier-2003">{{cite magazine |last=Montpellier |first=Emile Frison |title=Rescuing the banana |magazine=[[New Scientist]] |date=February 8, 2003 |url=https://www.newscientist.com/article/mg17723813.300-rescuing-the-banana.html |access-date=December 9, 2006 |url-status=dead |archive-url=https://web.archive.org/web/20070311123354/http://www.newscientist.com/article/mg17723813.300-rescuing-the-banana.html |archive-date=March 11, 2007  }}</ref> Within the data gathered from the genes of hundreds of bananas, the botanist Julie Sardos has found several wild banana ancestors currently unknown to scientists, whose genes could provide a means of defense against banana crop diseases.<ref>{{Cite news |last=Whang |first=Oliver |date=October 17, 2022 |title=The Search Is on for Mysterious Banana Ancestors |work=[[The New York Times]] |url=https://www.nytimes.com/2022/10/17/science/banana-ancestors-genes.html |access-date=October 21, 2022}}</ref>

Some commentators have remarked that those variants which could replace what much of the world considers a "typical banana" are so different that most people would not consider them the same fruit, and blame the decline of the banana on [[mendelian inheritance|monogenetic]] cultivation driven by short-term commercial motives.<ref name="NZHerald-2008">{{cite news |title=Big-business greed killing the banana – Independent |newspaper=[[The New Zealand Herald]] |date=May 24, 2008 |page=A19}}</ref> Overall, [[fungal banana disease|fungal diseases]] are disproportionately important to [[small island developing states]].<ref name="Thomas-2020">{{cite journal |last1=Thomas |first1=Adelle |last2=Baptiste |first2=April |last3=Martyr-Koller |first3=Rosanne |last4=Pringle |first4=Patrick |last5=Rhiney |first5=Kevon |title=Climate Change and Small Island Developing States |journal=[[Annual Review of Environment and Resources]] |publisher=[[Annual Reviews (publisher)|Annual Reviews]] |volume=45 |issue=1 |date=October 17, 2020 |doi=10.1146/annurev-environ-012320-083355 |pages=1–27 |doi-access=free }}</ref>

=== Panama disease ===

[[File:Panama disease of banana - vascular decoloration on pseudostem.jpg|thumb|Panama disease ''[[Fusarium]]'' fungus climbing up through the banana stem |alt=A banana tree cut horizontally to show the fungus development in the interior of the tree]]

[[Panama disease]] is caused by a ''[[Fusarium]]'' soil [[fungus]], which enters the plants through the roots and travels with water into the trunk and leaves, producing [[gel]]s and gums that cut off the flow of water and nutrients, causing the plant to [[wilting|wilt]], and exposing the rest of the plant to lethal amounts of sunlight. Prior to 1960, almost all commercial banana production centered on the Gros Michel cultivar, which was highly susceptible.<ref name="Barker-2008">{{cite journal |last=Barker |first=C.L. |title=Conservation: Peeling Away |journal=National Geographic Magazine |date=November 2008}}</ref> Cavendish was chosen as the replacement for Gros Michel because, among resistant cultivars, it produces the highest quality [[fruit]]. It requires more care during shipping,<ref>{{cite magazine |first=Natasha |last=Frost |date=February 28, 2018 |url=https://www.atlasobscura.com/articles/gros-michel-bananas |magazine=[[Atlas Obscura]] |title=A Quest for the Gros Michel, the Great Banana of Yesteryear|access-date=July 24, 2019|archive-date=July 24, 2020 |archive-url=https://web.archive.org/web/20200724111647/https://www.atlasobscura.com/articles/gros-michel-bananas |url-status=live}}</ref> and its quality compared to Gros Michel is debated.<ref name="Lessard-1992">{{Cite book |title=The Complete Book of Bananas |last=Lessard |first=William |year=1992 |publisher=W.O. Lessard |isbn=978-0963316103 |pages=27–28}}</ref>

==== Fusarium wilt TR4 ====

[[Tropical Race 4|Fusarium wilt TR4]], a reinvigorated strain of Panama disease, was discovered in 1993. This virulent form of Fusarium wilt has destroyed Cavendish plantations in several southeast Asian countries and spread to Australia and India.<ref name="Karp-2019">{{cite web |url=https://www.nationalgeographic.com/environment/2019/08/banana-fungus-latin-america-threatening-future/ |title=The banana is one step closer to disappearing |last=Karp |first=Myles |publisher=[[National Geographic]] |date=August 12, 2019 |access-date=September 14, 2019 |archive-date=September 13, 2019 |archive-url=https://web.archive.org/web/20190913225425/https://www.nationalgeographic.com/environment/2019/08/banana-fungus-latin-america-threatening-future/ |url-status=dead}}</ref> As the soil-based fungi can easily be carried on boots, clothing, or tools, the wilt spread to the Americas despite years of preventive efforts.<ref name="Karp-2019"/> Without genetic diversity, Cavendish is highly susceptible to TR4, and the disease endangers its commercial production worldwide.<ref name="IBP-2012">{{cite web |title=Risk assessment of Eastern African Highland Bananas and Plantains against TR4 |publisher=[[International Tropical Fruits Network|International Banana Symposium]] |date=2012 |url=http://banana-networks.org/bapnet/files/2012/11/Risk-Assessment-EAHB1.pdf |access-date=April 6, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140407090355/http://banana-networks.org/bapnet/files/2012/11/Risk-Assessment-EAHB1.pdf |archive-date=April 7, 2014  }}</ref> The only known defense to TR4 is [[Plant disease resistance|genetic resistance]].<ref name="Karp-2019"/> This is conferred either by [[RGA2]], a gene isolated from a TR4-resistant [[diploid]] banana, or by the [[nematode]]-derived Ced9.<ref name="Dale-2017"/><ref name="ISAAA-2021"/> This may be achieved by [[genetic modification]].<ref name="Dale-2017">{{cite journal |display-authors=3 |last1=Dale |first1=James |last2=James |first2=Anthony |last3=Paul |first3=Jean-Yves |last4=Khanna |first4=Harjeet |last5=Smith |first5=Mark |last6=Peraza-Echeverria |first6=Santy |last7=Garcia-Bastidas |first7=Fernando |last8=Kema |first8=Gert |last9=Waterhouse |first9=Peter |last10=Mengersen |first10=Kerrie |last11=Harding |first11=Robert |title=Transgenic Cavendish bananas with resistance to Fusarium wilt tropical race 4 |journal=[[Nature Communications]] |date=November 14, 2017 |volume=8 |issue=1 |pages=1496 |doi=10.1038/s41467-017-01670-6 |pmid=29133817 |pmc=5684404 |bibcode=2017NatCo...8.1496D}}</ref><ref name="ISAAA-2021">{{cite web |title=Researchers Develop Cavendish Bananas Resistant to Panama Disease |website=ISAAA ([[International Service for the Acquisition of Agri-biotech Applications]]) Crop Biotech Update |date=2021-02-24 |url=http://www.isaaa.org/kc/cropbiotechupdate/article/default.asp?ID=18606 |access-date=2021-09-02}}</ref>

=== Black sigatoka ===

[[File:Black Sigatoka (detail).jpg|thumb|Leaf infected with [[black sigatoka]] ]]

[[Black sigatoka]] is a fungal leaf spot disease first observed in Fiji in 1963 or 1964. It is caused by the [[ascomycete]] ''Mycosphaerella fijiensis''. The disease, also called black leaf streak, has spread to banana plantations throughout the tropics from infected banana leaves used as packing material. It affects all main cultivars of bananas and plantains (including the Cavendish cultivars<ref name="Holmes-2013">{{cite journal |last=Holmes |first=Bob |date=April 20, 2013 |title=Go Bananas |journal=[[New Scientist]] |volume=218 |issue=2913 |pages=9–41}} (Also at {{cite web |last=Holmes |first=Bob |date=April 20, 2013 |title=Nana from heaven? How our favourite fruit came to be |website=[[New Scientist]] |url=https://www.newscientist.com/article/mg21829132.000-nana-from-heaven-how-our-favourite-fruit-came-to-be.html |access-date=April 19, 2013 |url-access=subscription |url-status=live |archive-url=https://web.archive.org/web/20130424064954/http://www.newscientist.com/article/mg21829132.000-nana-from-heaven-how-our-favourite-fruit-came-to-be.html |archive-date=April 24, 2013}})</ref>), impeding [[photosynthesis]] by blackening parts of the leaves, eventually killing the entire leaf. Starved for energy, fruit production falls by 50% or more, and the bananas that do grow [[ripen]] prematurely, making them unsuitable for export. The fungus has shown ever-increasing resistance to treatment; spraying with fungicides may be required as often as 50 times a year. Better strategies, with [[integrated pest management]], are needed.<ref>{{cite journal |last1=Marín |first1=D.H. |last2=Romero |first2=R. A. |last3=Guzmán |first3=M. |last4=Sutton |first4=T.B. |publisher=[[American Phytopathological Society]] (APS) |journal=[[Plant Disease (journal)|Plant Disease]] |title=Black sigatoka: An increasing threat to banana cultivation |volume=87 |issue=3 |pages=208–222 |year=2003 |doi=10.1094/PDIS.2003.87.3.208 |pmid=30812750 |bibcode=2003PlDis..87..208M }}</ref><ref name="JGI-2013">{{cite web |url=http://genomeportal.jgi-psf.org/Mycfi2/Mycfi2.home.html |title=''Mycosphaerella fijiensis'' v2.0 |publisher=[[Joint Genome Institute]], U.S. Department of Energy |year=2013 |access-date=13 August 2013 |archive-url=https://web.archive.org/web/20140228220104/http://genomeportal.jgi-psf.org/Mycfi2/Mycfi2.home.html |archive-date=28 February 2014 |url-status=dead }}</ref>

=== Banana bunchy top virus ===

[[File:Banana aphid colony.jpg|alt=Infected Banana Plant|thumb|Colony of banana aphids (''[[Pentalonia nigronervosa]]''), [[Disease vector|vector]] of [[banana bunchy top virus]] ]]

[[Banana bunchy top virus]] is a plant virus of the genus ''Babuvirus'', family ''Nanonviridae'' affecting ''Musa'' spp. (including banana, abaca, plantain and ornamental bananas) and ''Ensete'' spp. in the family ''Musaceae''.<ref>National Biological Information Infrastructure & IUCN/SSC Invasive Species Specialist Group. [http://www.issg.org/database/species/ecology.asp?si=141 Banana Bunchy Top Virus] {{Webarchive |url=https://web.archive.org/web/20160422084515/http://www.issg.org/database/species/ecology.asp?si=141 |date=April 22, 2016}}. Global Invasive Species Database. N.p., July 6, 2005.</ref> Banana bunchy top disease symptoms include dark green streaks of variable length in leaf veins, midribs and petioles. Leaves become short and stunted as the disease progresses, becoming 'bunched' at the apex of the plant. Infected plants may produce no fruit or the fruit bunch may not emerge from the pseudostem.<ref name="Thomas-2015">Thomas, J.E. (ed). 2015. [http://www.musalit.org/seeMore.php?id=15942 MusaNet Technical Guidelines for the Safe Movement of ''Musa'' Germplasm] {{Webarchive |url=https://web.archive.org/web/20180928035947/http://www.musalit.org/seeMore.php?id=15942 |date=September 28, 2018}}. 3rd edition. MusaLit, Bioversity International, Rome</ref> The virus is transmitted by the banana aphid ''[[Pentalonia nigronervosa]]'' and is widespread in Southeast Asia, Asia, the Philippines, Taiwan, Oceania and parts of Africa. There is no cure, but it can be effectively controlled by the eradication of diseased plants and the use of virus-free planting material.<ref>{{cite web |last1=Thomas |first1=J.E. |last2=Iskra-Caruana |first2=M-L. |first3=D.R. |last3=Jones |year=1994 |title=''Musa'' Disease Fact Sheet N° 4. Banana Bunchy Top Disease |publisher=[[INIBAP]] |url=https://www.bioversityinternational.org/fileadmin/user_upload/online_library/publications/pdfs/703.pdf |access-date=October 2, 2018 |archive-date=October 2, 2018 |archive-url=https://web.archive.org/web/20181002180558/https://www.bioversityinternational.org/fileadmin/user_upload/online_library/publications/pdfs/703.pdf |url-status=live}}</ref> No resistant cultivars have been found, but varietal differences in susceptibility have been reported. The commercially important Cavendish subgroup is severely affected.<ref name="Thomas-2015"/>

=== Banana bacterial wilt ===

[[Banana Xanthomonas wilt|Banana bacterial wilt]] is a bacterial disease caused by ''[[Xanthomonas campestris]]'' pv. ''musacearum''.<ref name="Tushemereirwe-2004">{{Cite journal |last1=Tushemereirwe |first1=W. |last2=Kangire |first2=A. |last3=Ssekiwoko |first3=F. |last4=Offord |first4=L.C. |last5=Crozier |first5=J. |last6=Boa |first6=E. |last7=Rutherford |first7=M. |last8=Smith |first8=J.J. |title=First report of ''Xanthomonas campestris'' pv. ''musacearum'' on banana in Uganda |journal=[[Plant Pathology (journal)|Plant Pathology]] |volume=53 |date=2004 |page=802 |doi=10.1111/j.1365-3059.2004.01090.x |issue=6|bibcode=2004PPath..53..802T }}</ref> First identified on a close relative of bananas, ''[[Ensete ventricosum]]'', in Ethiopia in the 1960s,<ref name="Bradbury-1968">{{Cite journal |last1=Bradbury |first1=J.F. |last2=Yiguro |first2=D. |title=Bacterial wilt of Enset (''Ensete ventricosa'') incited by ''Xanthomonas musacearum'' |journal=[[Phytopathology (journal)|Phytopathology]] |volume=58 |date=1968 |pages=111–112}}</ref> The disease was first seen in Uganda in 2001 affecting all banana cultivars. Since then it has been diagnosed in Central and East Africa, including the banana growing regions of Rwanda, the Democratic Republic of the Congo, Tanzania, Kenya, Burundi, and Uganda.<ref name="Mwangi-2007">{{Cite journal |last1=Mwangi |first1=M. |last2=Bandyopadhyay |first2=R. |last3=Ragama |first3=P. |last4=Tushemereirwe |first4=R.K. |title=Assessment of banana planting practices and cultivar tolerance in relation to management of soilborne ''Xanthomonas campestris'' pv. ''musacearum'' |journal=[[Crop Protection (journal)|Crop Protection]] |volume=26 |date=2007 |pages=1203–1208 |doi=10.1016/j.cropro.2006.10.017 |issue=8  |bibcode=2007CrPro..26.1203M }}</ref>