Editing Cassava

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|image2_alt=Photograph of oblong brown tuberous root, waxed

'''''Manihot esculenta''''', [[common name|commonly called]] '''cassava''', '''manioc''',<!--<ref name=GRIN>{{GRIN |access-date=4 January 2014}}</ref>--> or '''yuca''' (among numerous regional names), is a woody [[shrub]] of the [[spurge]] family, [[Euphorbiaceae]], native to South America, from Brazil, Paraguay and parts of the Andes. Although a perennial plant, cassava is extensively cultivated in [[tropical]] and [[subtropical]] regions as an annual [[crop]] for its edible [[starch]]y [[tuber]]ous root. Cassava is predominantly consumed in boiled form, but substantial quantities are processed to extract cassava starch, called [[tapioca]], which is used for food, animal feed, and industrial purposes. The Brazilian {{lang|pt-BR|farofa}}, and the related ''[[garri]]'' of West Africa, is an edible coarse flour obtained by grating cassava roots, pressing moisture off the obtained grated pulp, and finally drying it (and roasting in the case of both {{lang|pt-BR|farofa}} and ''garri'').

Cassava is the third-largest source of carbohydrates in food in the tropics, after [[rice]] and [[maize]], making it an important [[staple food|staple]]; more than 500 million people depend on it. It offers the advantage of being exceptionally [[drought-tolerant]], and able to grow productively on poor soil. The largest producer is Nigeria, while Thailand is the largest exporter of cassava starch.

== Etymology ==

The [[genus|generic]] name ''[[Manihot]]'' and the common name "manioc" both derive from the [[Guarani language|Guarani]] (Tupi) name ''mandioca'' or ''manioca'' for the plant.<ref name="SNP"/><ref>{{cite web |title=manioc (n.) |url=https://www.etymonline.com/word/manioc|publisher=[[Online Etymology Dictionary]] |access-date=7 July 2024}}</ref> The specific name ''esculenta'' is Latin for 'edible'.<ref name="SNP">{{cite web |title=''Manihot esculenta'' Crantz |publisher=Singapore National Parks |url=https://www.nparks.gov.sg/florafaunaweb/flora/2/2/2210 |access-date=7 July 2024 |quote=Genus Manihot is from the Tupi-Guarani name "manioca" which means cassava. Species esculenta means edible by humans.}}</ref> The common name "cassava" is a 16th century word from the French or Portuguese ''cassave'', in turn from [[Taíno]] ''caçabi''.<ref>{{cite web |title=cassava (n.) |url=https://www.etymonline.com/word/cassava |publisher=[[Online Etymology Dictionary]] |access-date=7 July 2024}}</ref> The common name "yuca" or "yucca" is most likely also from Taíno, via Spanish ''yuca'' or ''juca''.<ref>{{cite web |title=yucca (n.) |url=https://www.etymonline.com/word/yucca |publisher=[[Online Etymology Dictionary]] |access-date=7 July 2024}}</ref>

== Description ==

The harvested part of a cassava plant is the root. This is long and tapered, with an easily detached rough brown rind. The white or yellowish flesh is firm and even in texture. Commercial [[cultivar]]s can be {{convert|5|to|10|cm|in|0}} wide at the top, and some {{convert|15|to|30|cm|in|0|abbr=on}} long, with a woody vascular bundle running down the middle. The [[tuber]]ous roots are largely [[starch]], with small amounts of calcium (16&nbsp;milligrams per 100&nbsp;grams), phosphorus (27&nbsp;mg/100&nbsp;g), and [[Vitamin C|vitamin&nbsp;C]] (20.6&nbsp;mg/100&nbsp;g).<ref>{{cite web|title=Basic Report: 11134, Cassava, raw|url=https://ndb.nal.usda.gov/ndb/foods/show/2907?manu=&fgcd=&ds=|archive-url=https://web.archive.org/web/20170712215400/https://ndb.nal.usda.gov/ndb/foods/show/2907?manu=&fgcd=&ds=|archive-date=12 July 2017|website=National Nutrient Database for Standard Reference Release 28|date=May 2016|publisher=Agricultural Research Service, US Department of Agriculture|access-date=7 December 2016}}</ref> Cassava roots contains little [[protein]], whereas the leaves are rich in it,<ref>{{Cite journal |last1=Latif |first1=Sajid |last2=Müller |first2=Joachim |title=Potential of cassava leaves in human nutrition: a review |journal=[[Trends in Food Science & Technology]] |year=2015 |volume=44 |issue=2 |pages=147–158 |doi=10.1016/j.tifs.2015.04.006 }}</ref> except for being low in [[methionine]], an essential [[amino acid]].<ref>{{Cite journal|last=Ravindran|first=Velmerugu |title=Preparation of cassava leaf products and their use as animal feeds |journal=FAO Animal Production and Health Paper |issue=95 |pages=111–125 |year=1992 |url=http://www.fao.org/Ag/AGA/AGAP/FRG/AHPP95/95-111.pdf |access-date=13 August 2010 |archive-date=15 January 2012 |archive-url=https://web.archive.org/web/20120115022720/http://www.fao.org/Ag/AGA/AGAP/FRG/AHPP95/95-111.pdf |url-status=dead}}</ref>

File:Manihot esculenta dsc07325.jpg|Unprocessed tuberous roots

File:Manihot esculenta - cross section 2.jpg|Tuberous root in cross-section

The complete and haplotype-resolved African cassava (TME204) genome has been reconstructed and made available using the Hi-C technology.<ref name="qi">{{Cite journal |last1=Qi |first1=W. |last2=Lim |first2=Y. |last3=Patrignani |first3=A. |last4=Schläpfer |first4=P. |last5=Bratus-Neuenschwander |first5=A. |last6=Grüter |first6=S. |last7=Chanez |first7=C. |last8=Rodde |first8=N. |last9=Prat |first9=E. |last10=Vautrin |first10=S. |last11=Fustier |first11=M. |last12=Pratas |first12=D. |last13=Schlapbach |first13=R. |last14=Gruissem |first14=W. |display-authors=5 |year=2022 |title=The haplotype-resolved chromosome pairs of a heterozygous diploid African cassava cultivar reveal novel pan-genome and allele-specific transcriptome features |journal=[[GigaScience]] |volume=11 |doi=10.1093/gigascience/giac028 |pmid=35333302 |pmc=8952263 }}</ref> The genome shows abundant novel gene loci with enriched functionality related to chromatin organization, meristem development, and cell responses.<ref name="qi" /> Differentially expressed transcripts of different haplotype origins were enriched for different functionality during tissue development. In each tissue, 20–30% of transcripts showed allele-specific expression differences with <2% of direction-shifting. Despite high gene synteny, the HiFi genome assembly revealed extensive chromosome rearrangements and abundant intra-genomic and inter-genomic divergent sequences, with significant structural variations mostly related to long terminal repeat retrotransposons.<ref name="qi" />

Although [[smallholder]]s are otherwise [[economic efficiency|economically inefficient]] producers, they are vital to productivity at particular times.<ref name="Challenges-Opportunities" /> Small cassava farmers are no exception.<ref name="Challenges-Opportunities" /> [[Crop genetic diversity|Genetic diversity]] is vital when productivity has declined due to [[crop pest|pests]] and [[List of cassava diseases|diseases]], and smallholders tend to retain less productive but more diverse [[gene pool]]s.<ref name="Challenges-Opportunities">{{cite journal |last1=McGregor |first1=Andrew |last2=Manley |first2=M. |last3=Tubuna |first3=S. |last4=Deo |first4=R. |last5=Bourke |first5=Mike |date=2020 |journal=Pacific Economic Bulletin|publisher=Asia Pacific Press |title=Pacific Island food security: situation, challenges and opportunities |hdl=1885/39234}}</ref>

{{ visible anchor |MeFT1 |MeFT2 |FLOWERING LOCUS T |FT |FT protein }} (FT) is a gene producing FT proteins which affect the formation of storage roots in many plants, including this one.<ref name="Development" /> Alleles in cassava include ''MeFT1'' and ''MeFT2''.<ref name="Development" /> ''MeFT1'' [[gene expression|expression]] in leaves seems to not be [[photoperiodic]], while ''MeFT2'' clearly is.<ref name="Development" /> ''MeFT1'' expression encourages motivation of [[sucrose]] towards the reproductive organs, as shown by experimental [[overexpression]] reducing storage root accumulation.<ref name="Development">{{cite journal |year=2021 |publisher=[[Annual Reviews (publisher)|Annual Reviews]] |issue=1 |volume=72 |pages=551–580 |first2=David |first4=Sophia |first1=Wolfgang |first3=Uwe |last4=Sonnewald |last3=Sonnewald |last2=Rüscher |last1=Zierer |issn=1543-5008 |journal=[[Annual Review of Plant Biology]] |doi=10.1146/annurev-arplant-080720-084456 |title=Tuber and Tuberous Root Development |pmid=33788583 |doi-access=free}}</ref>

[[File:Taíno women preparing cassava bread.png|thumb|[[Taíno]] women preparing [[cassava bread]] in 1565: grating tuberous roots into paste, shaping the bread, and cooking it on a fire-heated burén]]

Wild populations of ''M. esculenta'' subspecies ''flabellifolia'', shown to be the progenitor of domesticated cassava, are centered in west-central Brazil, where it was likely first domesticated no more than 10,000 years ago.<ref>{{Cite journal|last1=Olsen|first1=K. M. |last2=Schaal |first2=B. A. |title=Evidence on the origin of cassava: phylogeography of ''Manihot esculenta'' |journal=[[Proceedings of the National Academy of Sciences of the United States of America]]|volume=96 |issue=10 |pages=5586–5591 |year=1999 |pmid=10318928 |pmc=21904 |bibcode=1999PNAS...96.5586O |doi=10.1073/pnas.96.10.5586 |doi-access=free }}</ref> Forms of the modern domesticated species can also be found growing in the wild in the south of Brazil. By 4600&nbsp;BC, cassava pollen appears in the [[Gulf of Mexico]] lowlands, at the [[San Andrés (Mesoamerican site)|San Andrés]] archaeological site.<ref>{{cite journal |last1=Pope |first1=Kevin O. |last2=Pohl |first2=Mary E. D. |last3=Jones |first3=John G. |last4=Lentz |first4=David L. |last5=von Nagy |first5=Christopher |last6=Vega |first6=Francisco J. |last7=Quitmyer |first7=Irvy R. |title=Origin and Environmental Setting of Ancient Agriculture in the Lowlands of Mesoamerica |journal=[[Science (journal)|Science]] |volume=292 |issue=5520 |pages=1370–1373 |year=2001 |doi=10.1126/science.292.5520.1370 |pmid=11359011 |bibcode=2001Sci...292.1370P}}</ref> The oldest direct evidence of cassava cultivation comes from a 1,400-year-old [[Maya civilization|Maya]] site, [[Joya de Cerén]], in [[El Salvador]].<ref>{{cite news |last=Carroll |first=Rory |title=CU team discovers Mayan crop system |newspaper=[[The Guardian]] |date=23 August 2007 |url=https://www.theguardian.com/science/2007/aug/23/1 |access-date=31 July 2019 |archive-date=31 July 2019 |archive-url=https://web.archive.org/web/20190731171801/https://www.theguardian.com/science/2007/aug/23/1 |url-status=live }}</ref> It became a [[staple food]] of the native populations of northern South America, southern Mesoamerica, and the [[Taíno|Taino]] people in the [[List of Caribbean islands|Caribbean islands]], who grew it using a high-yielding form of [[shifting cultivation|shifting agriculture]] by the time of European contact in 1492.<ref>{{cite web |title=Taino {{!}} History & Culture |url=https://www.britannica.com/topic/Taino |access-date=2020-09-24 |website=Encyclopedia Britannica |archive-date=2020-09-01 |archive-url=https://web.archive.org/web/20200901154607/https://www.britannica.com/topic/Taino |url-status=live}}</ref> Cassava was a staple food of [[pre-Columbian]] peoples in the Americas and is often portrayed in [[Pre-Columbian art|indigenous art]]. The [[Moche (culture)|Moche]] people often depicted cassava in their ceramics.<ref>Berrin, Katherine & Larco Museum. ''The Spirit of Ancient Peru:Treasures from the [[Larco Museum|Museo Arqueológico Rafael Larco Herrera]].'' New York: [[Thames & Hudson]], 1997.</ref>

Portuguese traders introduced cassava to Africa from Brazil in the 16th century. Around the same period, it was introduced to Asia through [[Columbian Exchange]] by Portuguese and Spanish traders, who planted it in their colonies in Goa, Malacca, Eastern Indonesia, Timor and the Philippines.<ref name="Nweke 2005">{{cite book |last=Nweke |first=Felix I. |chapter=The cassava transformation in Africa |chapter-url=http://www.fao.org/docrep/009/a0154e/A0154E02.HTM |publisher=The Food and Agriculture Organization of the United Nations |place=Rome |year=2005 |title=A review of cassava in Africa with country case studies on Nigeria, Ghana, the United Republic of Tanzania, Uganda and Benin |series=Proceedings of the Validation Forum on the Global Cassava Development Strategy |volume=2 |access-date=1 January 2011 |archive-date=11 February 2019 |archive-url=https://web.archive.org/web/20190211073843/http://www.fao.org/docrep/009/a0154e/A0154E02.htm |url-status=live}}</ref> Cassava has also become an important crop in Asia. While it is a valued food staple in parts of eastern Indonesia, it is primarily cultivated for starch extraction and bio-fuel production in Thailand, Cambodia and Vietnam.<ref>{{Cite book |last=Hershey |first=Clair |display-authors=et al |date=April 2000 |chapter-url=http://www.fao.org/docrep/009/y1177e/Y1177E02.htm |publisher=Food and Agriculture Organization of the United Nations |title=A review of cassava in Asia with country case studies on Thailand and Viet Nam |chapter=Cassava in Asia. Expanding the Competitive Edge in Diversified Markets |place=Rome |access-date=28 January 2018 |archive-date=7 November 2017|archive-url=https://web.archive.org/web/20171107231144/http://www.fao.org/docrep/009/y1177e/Y1177E02.htm|url-status=live}}</ref> Cassava is sometimes described as the "bread of the tropics"<ref>{{Cite book |last1=Adams |first1=C. |last2=Murrieta |first2=R. |last3=Siqueira |first3=A. |last4=Neves |first4=W. |last5=Sanches |first5=R. |chapter=Bread of the Land: The Invisibility of Manioc in the Amazon |title=Amazon Peasant Societies in a Changing Environment |doi=10.1007/978-1-4020-9283-1_13 |pages=281–305 |year=2009 |isbn=978-1-4020-9282-4 }}</ref> but should not be confused with the tropical and equatorial [[bread tree]] ''(Encephalartos)'', the [[breadfruit]] ''(Artocarpus altilis)'' or the [[African breadfruit]] ''(Treculia africana)''. This description definitely holds in Africa and parts of South America; in Asian countries such as Vietnam fresh cassava barely features in human diets.<ref name=MotaGuttierez2019>{{cite journal |last1=Mota-Guttierez |first1=Jatziri |last2=O'Brien |first2=Gerard Michael |date=September 2019 |title=Cassava consumption and the occurrence of cyanide in cassava in Vietnam, Indonesia and Philippines |journal=Public Health Nutrition |volume=23 |issue=13 |pages=2410–2423 |doi=10.1017/S136898001900524X |doi-access=free |pmid=32438936 |pmc=11374567 }}</ref>

Several viruses cause enough damage to cassava crops to be of economic importance. The [[African cassava mosaic virus]] causes the leaves of the cassava plant to wither, limiting the growth of the root.<ref>{{cite web |title=Cassava (manioc) |url=https://www.plantvillage.com/en/topics/cassava-manioc/infos/diseases_and_pests_description_uses_propagation |archive-url=https://web.archive.org/web/20150630145744/https://www.plantvillage.com/en/topics/cassava-manioc/infos/diseases_and_pests_description_uses_propagation |archive-date=30 June 2015 |access-date=29 May 2015}}</ref> An outbreak of the virus in Africa in the 1920s led to a major famine.<ref name="NYT May 2010">{{cite news |date=31 May 2010 |title=Virus ravages cassava plants in Africa |work=The New York Times |url=https://www.nytimes.com/2010/06/01/science/01cassava.html |access-date=24 February 2017 |archive-date=16 March 2017 |archive-url=https://web.archive.org/web/20170316113128/http://www.nytimes.com/2010/06/01/science/01cassava.html |url-status=live }}</ref> The virus is spread by the [[whitefly]] and by the transplanting of diseased plants into new fields. Sometime in the late-1980s, a mutation occurred in Uganda that made the virus even more harmful, causing the complete loss of leaves. This mutated virus spread at a rate of {{convert|50|mi|km|sigfig=1|order=flip|abbr=off}} per year, and as of 2005 was found throughout Uganda, Rwanda, Burundi, the Democratic Republic of the Congo and the Republic of the Congo.<ref>{{cite web |date=31 August 2005 |title=Hungry African nations balk at biotech cassava |url=http://www.redorbit.com/news/science/225369/hungry_african_nations_balk_at_biotech_cassava/ |archive-url=https://web.archive.org/web/20120303183231/http://www.redorbit.com/news/science/225369/hungry_african_nations_balk_at_biotech_cassava/ |archive-date=3 March 2012 |access-date=11 August 2008 |work=[[St. Louis Post-Dispatch]]}}</ref> Viruses are a severe production limitation in the tropics. They are the primary reason for the complete lack of yield increases in the 25 years {{as of|2021|alt=up to 2021}}.<ref name="Afedraru-2019" /> [[Cassava brown streak virus disease]] is a major threat to cultivation worldwide.<ref name="NYT May 2010" /> [[Cassava mosaic virus]] (CMV) is widespread in Africa, causing cassava mosaic disease (CMD).<ref name="Lebot-2020" /> Bredeson et al. 2016 find the ''M. esculenta'' cultivars most widely used on that continent have [[Manihot carthaginensis subsp. glaziovii|''M. carthaginensis'' subsp. ''glaziovii'']] genes of which some appear to be CMD [[plant disease resistance gene|resistance gene]]s.<ref name="Lebot-2020">{{cite book |last=Lebot |first=Vincent |title=Tropical Root and Tuber Crops: Cassava, Sweet Potato, Yams And Aroids |publisher=CABI ([[Centre for Agriculture and Bioscience International]]) |year=2020 |isbn=978-1-78924-336-9 |publication-place=[[Wallingford, Oxfordshire]], UK; [[Boston]], USA |page=541 |oclc=1110672215}}</ref> Although the ongoing CMD [[pandemic]] affects both East and Central Africa, Legg ''et al.'' found that these two areas have two distinct [[subpopulation]]s of the [[vector (epidemiology)|vector]], ''[[Bemisia tabaci]]'' whiteflies.<ref>{{ Cite book |year=2015 |publisher=Academic Press |issn=0065-3527 |author1=Legg, James P. |author2=Kumar, P. Lava |author3=Makeshkumar, T. |author4=Tripathi, Leena |author5=Ferguson, Morag |author6=Kanju, Edward |author7=Ntawuruhunga, Pheneas |author8=Cuellar, Wilmer |doi=10.1016/bs.aivir.2014.10.001 |chapter=Cassava Virus Diseases: Biology, Epidemiology, and Management |editor1=Loebenstein, Gad |editor2=Katis, Nikolaos I. |series=Control of Plant Virus Diseases: Vegetatively-Propagated Crops |title=Advances in Virus Research |volume=91 |pages=85–142 |pmid=25591878 |isbn=9780128027622}}</ref><ref name="Legg 2014">{{cite journal |last1=Legg |first1=James P. |last2=Sseruwagi |first2=Peter |last3=Boniface |first3=Simon |last4=Okao-Okuja |first4=Geoffrey |last5=Shirima |first5=Rudolph |last6=Bigirimana |first6=Simon |last7=Gashaka |first7=Gervais |last8=Herrmann |first8=Hans-Werner |last9=Jeremiah |first9=Simon |last10=Obiero |first10=Hannington |last11=Ndyetabula |first11=Innocent |last12=Tata-Hangy |first12=Willy |last13=Masembe |first13=Charles |last14=Brown |first14=Judith K. |display-authors=6 |title=Spatio-temporal patterns of genetic change amongst populations of cassava Bemisia tabaci whiteflies driving virus pandemics in East and Central Africa |journal=Virus Research |volume=186 |date=2014 |doi=10.1016/j.virusres.2013.11.018 |pages=61–75 |pmid=24291251 }}</ref> Genetically engineered cassava offers opportunities for the improvement of virus resistance, including CMV and CBSD resistance.<ref name="Current-Perspectives">{{cite journal |last1=Rey |first1=Chrissie |last2=Vanderschuren |first2=Hervé |title=Cassava Mosaic and Brown Streak Diseases: Current Perspectives and Beyond |issue=1 |volume=4 |year=2017 |pages=429–452 |publisher=[[Annual Reviews (publisher)|Annual Reviews]] |journal=[[Annual Review of Virology]] |issn=2327-056X |s2cid=25767024 |pmid=28645239 |doi=10.1146/annurev-virology-101416-041913 |doi-access=free}}</ref>

Among the most serious bacterial pests is [[Xanthomonas axonopodis pv. manihotis|''Xanthomonas axonopodis'' pv. ''manihotis'']], which causes [[bacterial blight of cassava]]. This disease originated in South America and has followed cassava around the world.<ref name="Lozano-1986">{{Cite journal |last=Lozano |first=J. Carlos |date=September 1986 |title=Cassava bacterial blight: a manageable disease |url=http://www.apsnet.org/publications/PlantDisease/BackIssues/Documents/1986Articles/PlantDisease70n12_1089.PDF |journal=[[Plant Disease (journal)|Plant Disease]] |publisher=[[American Phytopathological Society]] (APS) |volume=70 |issue=12 |pages=1089–1093 |doi=10.1094/PD-70-1089 |access-date=14 January 2023 |archive-date=14 January 2023 |archive-url=https://web.archive.org/web/20230114224139/https://www.apsnet.org/publications/PlantDisease/BackIssues/Documents/1986Articles/PlantDisease70n12_1089.PDF |url-status=live }}</ref> Bacterial blight has been responsible for near catastrophic losses and famine in past decades, and its mitigation requires active management practices.<ref name="Lozano-1986" /> Several other bacteria attack cassava, including the related ''[[Xanthomonas campestris]]'' pv. ''cassavae'', which causes bacterial angular leaf spot.<ref name="Zárate-Chaves 2021">{{cite journal |last1=Zárate-Chaves |first1=Carlos A. |last2=Gómez de la Cruz |first2=Diana |last3=Verdier |first3=Valérie |last4=López |first4=Camilo E. |last5=Bernal |first5=Adriana |last6=Szurek |first6=Boris |title=Cassava diseases caused by Xanthomonas phaseoli pv. manihotis and Xanthomonas cassavae |journal=Molecular Plant Pathology |volume=22 |issue=12 |date=2021 |issn=1464-6722 |pmid=34227737 |pmc=8578842 |doi=10.1111/mpp.13094 |pages=1520–1537}}</ref>

Several fungi bring about significant crop losses, one of the most serious being cassava root rot; the [[pathogen]]s involved are species of ''[[Phytophthora]]'', the genus which causes potato blight. Cassava root rot can result in losses of as much as 80 percent of the crop.<ref name="Alvarez 2012">{{cite book|last1=Alvarez |first1=Elizabeth |author2=Llano, Germán Alberto |author3=Mejía, Juan Fernando |chapter=Cassava diseases in Latin America, Africa and Asia |title=The Cassava Handbook |page=258 |year=2012 |url=https://www.academia.edu/download/98098352/The_Cassava_Handbook_2011.pdf#page=266}}<!--Scholar: cassava fungal diseases--></ref>

Nematode pests of cassava are thought to cause harms ranging from negligible to seriously damaging,<ref>{{cite journal |author1=Coyne, D. L. |author2=Talwana, L. A. H. |date=2000 |title=Reaction of cassava cultivars to root-knot nematode (''Meloidogyne'' spp.) in pot experiments and farmer-managed field trials in Uganda |journal=International Journal of Nematology|volume=10 |pages=153–158 |url=https://www.cabdirect.org/cabdirect/abstract/20013117434 |access-date=22 September 2018}}</ref><ref>{{cite journal |author1=Makumbi-Kidza, N. N. |author2=Speijer |author3=Sikora R. A. |date=2000 |title=Effects of ''Meloidogyne incognita'' on growth and storage-root formation of cassava (''Manihot esculenta'') |journal=Journal of Nematology|volume=32 |issue=4S |pages=475–477 |pmc=2620481 |pmid=19270997}}</ref><ref name="Gapasin"/> making the choice of management methods difficult.<ref name="Coyne"/> A wide range of plant parasitic nematodes have been reported associated with cassava worldwide. These include ''[[Pratylenchus brachyurus]]'', ''[[Rotylenchulus reniformis]]'', ''[[Helicotylenchus]]'' spp., ''[[Scutellonema]]'' spp. and ''[[Root-knot nematode|Meloidogyne]]'' spp., of which ''[[Meloidogyne incognita]]'' and ''[[Meloidogyne javanica]]'' are the most widely reported and economically important.<ref>{{cite journal |author1=Mc Sorley, R. |author2=Ohair, S. K. |author3=Parrado, J. L. |date=1983 |title=Nematodes of Cassava, ''Manihot esculenta'' Crantz |url=http://journals.fcla.edu/nematropica/article/view/63820/61488 |journal=Nematropica|volume=13 |pages=261–287 |archive-url=https://web.archive.org/web/20160603205439/http://journals.fcla.edu/nematropica/article/view/63820/61488 |archive-date=3 June 2016 |access-date=4 May 2016}}</ref> ''Meloidogyne'' spp. feeding produces physically damaging galls with eggs inside them. Galls later merge as the females grow and enlarge, and they interfere with water and nutrient supply.<ref name="Gapasin">{{cite journal |author1=Gapasin, R. M. |date=1980 |title=Reaction of golden yellow cassava to ''Meloidogyne'' spp. Inoculation |journal=Annals of Tropical Research|volume=2 |pages=49–53}}</ref> Cassava roots become tough with age and restrict the movement of the juveniles and the egg release. It is therefore possible that extensive galling can be observed even at low densities following infection.<ref name="Coyne">{{cite journal |author1=Coyne, D. L. |date=1994 |title=Nematode pests of cassava |journal=African Crop Science Journal|volume=2 |issue=4 |pages=355–359 |url=https://www.ajol.info/index.php/acsj/article/view/135776 |access-date=22 September 2018 |archive-date=22 September 2018 |url-status=live |archive-url=https://web.archive.org/web/20180922101847/https://www.ajol.info/index.php/acsj/article/view/135776}}</ref> Other pests and diseases can gain entry through the physical damage caused by gall formation, leading to rots. They have not been shown to cause direct damage to the enlarged tuberous roots, but plant height can be reduced if the root system is reduced.<ref>{{cite journal |author1=Caveness, F. E. |date=1982 |title=Root-knot nematodes as parasites of cassava |journal=IITA Research Briefs|volume=3 |issue=2 |pages=2–3}}</ref>

Nematicides reduce the numbers of galls per feeder root, along with fewer rots in the tuberous roots.<ref>{{cite journal |author1=Coyne D. L. |author2=Kagoda F. |author3=Wambugu E. |author4=Ragama P. |date=2006 |title=Response of cassava to nematicide application and plant-parasitic nematode infection in East Africa, with emphasis on root-knot nematode |journal=International Journal of Pest Management |volume=52 |issue=3 |pages=215–223 |doi=10.1080/09670870600722959 |s2cid=84771539}}</ref> The organophosphorus nematicide femaniphos does not reduce crop growth or harvest yield. Nematicide use in cassava is not terribly effective at increasing harvested yield, but lower infestation at harvest and lower subsequent storage loss provide a higher effective yield. The use of tolerant and resistant cultivars is the most practical management method in most locales.<ref name="Coyne-et-al-2018">{{cite journal |last1=Coyne |first1=Danny L. |last2=Cortada |first2=Laura |last3=Dalzell |first3=Johnathan J. |last4=Claudius-Cole |first4=Abiodun O. |last5=Haukeland |first5=Solveig |last6=Luambano |first6=Nessie |last7=Talwana |first7=Herbert |date=2018-08-25 |title=Plant-Parasitic Nematodes and Food Security in Sub-Saharan Africa |journal=[[Annual Review of Phytopathology]] |publisher=[[Annual Reviews (publisher)|Annual Reviews]] |volume=56 |issue=1 |pages=381–403 |doi=10.1146/annurev-phyto-080417-045833 |issn=0066-4286 |pmc=7340484 |pmid=29958072 |s2cid=49615468}}</ref><ref name="Coyne"/><ref name="TodayNg-new-varieties">{{cite web |url=http://www.today.ng/news/nigeria/nigeria-introduce-cassava-varieties-334463 |title=Nigeria to introduce new cassava varieties |website=Todayng |date=2020-12-21 |first=Chidinma |last=Uchechukwumgemezu |access-date=21 December 2020 |archive-date=21 December 2020 |archive-url=https://web.archive.org/web/20201221194624/https://www.today.ng/news/nigeria/nigeria-introduce-cassava-varieties-334463 |url-status=live}}</ref>

Before harvest, the leafy stems are removed. The harvest is gathered by pulling up the base of the stem and cutting off the tuberous roots.<ref name=CIAT/>

Cassava deteriorates after harvest, when the tuberous roots are first cut. The healing mechanism produces [[coumaric acid]], which oxidizes and blackens the roots, making them inedible after a few days. This deterioration is related to the accumulation of [[reactive oxygen species]] initiated by cyanide release during mechanical harvesting. Cassava shelf life may be increased up to three weeks by overexpressing a cyanide-insensitive alternative oxidase, which suppressed ROS by 10-fold.<ref>{{cite journal |last1=Zidenga |first1=T |display-authors=etal |year=2012 |title=Extending cassava root shelf life via reduction of reactive oxygen species production |journal=[[Plant Physiology (journal)|Plant Physiology]]|volume=159 |issue=4 |pages=1396–1407 |doi=10.1104/pp.112.200345 |pmc=3425186 |pmid=22711743}}</ref> Post-harvest deterioration is a major obstacle to the export of cassava. Fresh cassava can be preserved like potato, using [[thiabendazole]] or bleach as a fungicide, then wrapping in plastic, freezing, or applying a wax coating.<ref>{{cite web |title=Storage and processing of roots and tubers in the tropics |url=http://www.fao.org/docrep/x5415e/x5415e04.htm |access-date=4 May 2016 |publisher=[[U.N. Food and Agriculture Organization]] |archive-date=22 April 2016 |archive-url=https://web.archive.org/web/20160422120308/http://www.fao.org/docrep/x5415e/x5415e04.htm |url-status=live }}</ref>

While alternative methods for controlling post-harvest deterioration have been proposed, such as preventing reactive oxygen species effects by using plastic bags during storage and transport, coating the roots with wax, or freezing roots, such strategies have proved to be economically or technically impractical, leading to [[plant breeding|breeding]] of cassava varieties with improved durability after harvest, achieved by different mechanisms.<ref name="gmr">{{cite journal |last1=Venturini |first1=M. T |last2=Santos |first2=L. R |last3=Vildoso |first3=C. I |last4=Santos |first4=V. S |last5=Oliveira |first5=E. J |year=2016 |title=Variation in cassava germplasm for tolerance to post-harvest physiological deterioration |journal=[[Genetics and Molecular Research]] |volume=15 |issue=2 |doi=10.4238/gmr.15027818 |pmid=27173317 |doi-access=free}}</ref><ref name="cs">{{cite journal |last1=Morante |first1=N. |last2=Sánchez |first2=T. |last3=Ceballos |first3=H. |last4=Calle |first4=F. |last5=Pérez |first5=J. C. |last6=Egesi |first6=C. |last7=Cuambe |first7=C. E. |last8=Escobar |first8=A. F. |last9=Ortiz |first9=D. |last10=Chávez |first10=A. L. |last11=Fregene |first11=M. |year=2010 |title=Tolerance to Postharvest Physiological Deterioration in Cassava Roots |journal=[[Crop Science (journal)|Crop Science]]|volume=50 |issue=4 |pages=1333–1338 |doi=10.2135/cropsci2009.11.0666}}</ref> One approach used [[gamma ray]]s to try to silence a gene involved in triggering deterioration; another strategy selected for plentiful [[carotenoid]]s, [[antioxidant]]s which may help to reduce oxidization after harvest.<ref name="cs" />

In 2022, world production of cassava root was 330 million tonnes, led by Nigeria with 18% of the total (table). Other major growers were Democratic Republic of the Congo and Thailand.

Cassava is the third-largest source of carbohydrates in food in the tropics, after [[rice]] and [[maize]].<ref name="FAO">{{cite web|title=Cassava|publisher=[[Food and Agriculture Organization]] of the United Nations (FAO) |url=http://www.fao.org/ag/agp/agpc/gcds/|access-date=24 November 2011|archive-date=18 November 2016|archive-url=https://web.archive.org/web/20161118061344/http://www.fao.org/ag/agp/agpc/gcds/}}</ref><ref name="Claude-Denis-1990">{{cite journal |author1=Fauquet Claude |author2=Fargette Denis |year=1990 |title=African Cassava Mosaic Virus: Etiology, Epidemiology, and Control |url=http://www.apsnet.org/publications/PlantDisease/BackIssues/Documents/1990Articles/PlantDisease74n06_404.pdf |journal=[[Plant Disease (journal)|Plant Disease]] |publisher=[[American Phytopathological Society]] (APS) |volume=74 |issue=6 |pages=404–411 |doi=10.1094/pd-74-0404 |access-date=10 January 2011 |archive-date=9 August 2017 |archive-url=https://web.archive.org/web/20170809004240/http://www.apsnet.org/publications/PlantDisease/BackIssues/Documents/1990Articles/PlantDisease74n06_404.pdf |url-status=live }}</ref><ref name="Afedraru-2019">{{cite web |last=Afedraru |first=Lominda |title=Uganda to launch innovative gene-edited cassava research |website=Alliance for Science |date=2019-01-31 |url=http://allianceforscience.cornell.edu/blog/2019/01/uganda-launch-innovative-gene-edited-cassava-research/ |access-date=2021-08-15 |archive-date=15 August 2021 |archive-url=https://web.archive.org/web/20210815171521/https://allianceforscience.cornell.edu/blog/2019/01/uganda-launch-innovative-gene-edited-cassava-research/ |url-status=live }}</ref> making it an important staple; more than 500 million people depend on it.<ref>{{cite web|title=Dimensions of Need: An atlas of food and agriculture|publisher=United Nations [[Food and Agriculture Organization]] (FAO) |year=1995|url=http://www.fao.org/docrep/u8480e/U8480E01.htm|access-date=23 November 2011|archive-date=24 November 2016|archive-url=https://web.archive.org/web/20161124095410/http://www.fao.org/docrep/u8480e/U8480E01.htm|url-status=live}}</ref> It offers the advantage of being exceptionally [[drought-tolerant]], and able to grow productively on poor soil. Cassava grows well within 30° of the equator, where it can be produced at up to {{convert|2000|m|ft|sigfig=1|abbr=on}} above sea level, and with {{convert|50|to|5000|mm|in|sigfig=1|abbr=on}} of rain per year. These environmental tolerances suit it to conditions across much of South America and Africa.<ref>{{cite journal |last=Cock |first=James H. |title=Cassava |journal=The Crop Productivity Symposium, IRRI, los Banos, Philippines |date=September 1980 |pages=1–33 |url=https://cgspace.cgiar.org/server/api/core/bitstreams/0bb17dbb-ef96-4ea9-9ca6-100ae47f0503/content}} reprinted as a chapter in ''Crop physiology case histories for major crops''. [[Academic Press]], 2021, pages 588-633.</ref>

Chronic, low-level exposure to cyanide may contribute to both goiter and [[tropical ataxic neuropathy]], also called [[konzo]], which can be fatal. The risk is highest in famines, when as many as 3 percent of the population may be affected.<ref>{{cite web |last=Wagner |first=Holly |title=Cassava's cyanide-producing abilities can cause neuropathy |url=http://www.cidpusa.org/cassava.htm |archive-url=https://web.archive.org/web/20100924054056/http://cidpusa.org/cassava.htm |archive-date=24 September 2010 |access-date=21 June 2010 |publisher=cidpusa.org}}</ref><ref>{{cite journal |author1=Siritunga D |author2=Sayre RT |date=September–October 2007 |title=Transgenic approaches for cyanogen reduction in cassava |journal=[[J AOAC Int]] |volume=90 |issue=5 |pages=1450–1455 |doi=10.1093/jaoac/90.5.1450 |pmid=17955993 |doi-access=free}}</ref>

Societies that traditionally eat cassava generally understand that processing (soaking, cooking, fermentation, etc.) is necessary to avoid getting sick. Brief soaking (four hours) of cassava is not sufficient, but soaking for 18–24 hours can remove up to half the level of cyanide. Drying may not be sufficient, either.<ref name="fao.org"/>

For some smaller-rooted, sweet varieties, cooking is sufficient to eliminate all toxicity. The cyanide is carried away in the processing water and the amounts produced in domestic consumption are too small to have environmental impact.<ref name="cereda"/> The larger-rooted, bitter varieties used for production of flour or starch must be processed to remove the cyanogenic glucosides. The large roots are peeled and then ground into flour, which is then soaked in water, squeezed dry several times, and toasted. The starch grains that flow with the water during the soaking process are also used in cooking.<ref>{{Cite journal |last1=Padmaja |first1=G. |last2=Steinkraus |first2=K. H. |year=1995 |title=Cyanide detoxification in cassava for food and feed uses |journal=[[Critical Reviews in Food Science and Nutrition]]|volume=35 |issue=4 |pages=299–339 |doi=10.1080/10408399509527703 |pmid=7576161}}</ref> The flour is used throughout South America and the [[Caribbean]]. Industrial production of cassava flour, even at the cottage level, may generate enough cyanide and cyanogenic glycosides in the effluents to have a severe environmental impact.<ref name="cereda"/>

A safe processing method known as the "wetting method" is to mix the cassava flour with water into a thick paste, spread it in a thin layer over a basket and then let it stand for five hours at 30&nbsp;°C in the shade.<ref name="fca">{{cite journal |last1=Bradbury |first1=J.H. |date=2006 |title=Simple wetting method to reduce cyanogen content of cassava flour |url=http://biology-assets.anu.edu.au/hosted_sites/CCDN/papers/Howard_06.pdf |journal=[[Journal of Food Composition and Analysis]] |volume=19 |issue=4 |pages=388–393 |doi=10.1016/j.jfca.2005.04.012 |access-date=23 March 2018 |archive-date=5 February 2015 |archive-url=https://web.archive.org/web/20150205063243/http://biology-assets.anu.edu.au/hosted_sites/CCDN/papers/Howard_06.pdf |url-status=live }}</ref> In that time, about 83% of the cyanogenic [[glycoside]]s are broken down by [[linamarase]]; the resulting hydrogen cyanide escapes to the atmosphere, making the flour safe for consumption the same evening.<ref name="fca" />

The traditional method used in West Africa is to peel the roots and put them into water for three days to ferment. The roots are then dried or cooked. In Nigeria and several other west African countries, including Ghana, Cameroon, Benin, Togo, Ivory Coast, and Burkina Faso, they are usually grated and lightly fried in palm oil to preserve them. The result is a foodstuff called [[garri]]. Fermentation is also used in other places such as Indonesia, such as [[Tapai]]. The fermentation process also reduces the level of antinutrients, making the cassava a more nutritious food.<ref>{{cite journal |last1=Oboh |first1=G. |last2=Oladunmoye |first2=M.K. |title=Biochemical Changes in Micro-Fungi Fermented Cassava Flour Produced from Low- and Medium-Cyanide Variety of Cassava Tubers |journal=Nutrition and Health |volume=18 |issue=4 |date=2007 |issn=0260-1060 |doi=10.1177/026010600701800405 |pages=355–367|pmid=18087867 }}</ref> The reliance on cassava as a food source and the resulting exposure to the [[goitrogen]]ic effects of [[thiocyanate]] has been responsible for the endemic goiters seen in the [[Akoko]] area of southwestern Nigeria.<ref name="pmid10497657">{{cite journal |last1=Akindahunsi |first1=A. A. |last2=Grissom |first2=F. E. |last3=Adewusi |first3=S. R. |last4=Afolabi |first4=O. A. |last5=Torimiro |first5=S. E. |last6=Oke |first6=O. L. |title=Parameters of thyroid function in the endemic goitre of Akungba and Oke-Agbe villages of Akoko area of southwestern Nigeria |journal=African Journal of Medicine and Medical Sciences |volume=27 |issue=3–4 |date=1998 |issn=0309-3913 |pmid=10497657 |pages=239–242}}</ref><ref>{{cite journal |last1=Bumoko |first1=G.M.-M. |last2=Sadiki |first2=N.H. |last3=Rwatambuga |first3=A. |last4=Kayembe |first4=K.P. |last5=Okitundu |first5=D.L. |last6=Mumba Ngoyi |first6=D. |last7=Muyembe |first7=J.-J.T. |last8=Banea |first8=J.-P. |last9=Boivin |first9=M.J. |last10=Tshala-Katumbay |first10=D. |title=Lower serum levels of selenium, copper, and zinc are related to neuromotor impairments in children with konzo |journal=Journal of the Neurological Sciences |volume=349 |issue=1–2 |date=2015 |pmid=25592410 |pmc=4323625 |doi=10.1016/j.jns.2015.01.007 |pages=149–153}}</ref>

[[Bioengineering]] has been applied to grow cassava with lower [[cyanogenic glycosides]] combined with [[food fortification|fortification]] of [[vitamin A]], [[iron]] and protein to improve the nutrition of people in sub-Saharan Africa.<ref>{{Cite journal |last1=Sayre |first1=R. |last2=Beeching |first2=J. R. |last3=Cahoon |first3=E. B. |last4=Egesi |first4=C. |last5=Fauquet |first5=C. |last6=Fellman |first6=J. |last7=Fregene |first7=M. |last8=Gruissem |first8=W. |last9=Mallowa |first9=S. |last10=Manary |first10=M. |last11=Maziya-Dixon |first11=B. |year=2011 |title=The BioCassava Plus Program: Biofortification of Cassava for Sub-Saharan Africa |journal=[[Annual Review of Plant Biology]]|volume=62 |pages=251–272 |doi=10.1146/annurev-arplant-042110-103751 |pmid=21526968 |last12=Mbanaso |first12=A. |last13=Schachtman |first13=D. P. |last14=Siritunga |first14=D. |last15=Taylor |first15=N. |last16=Vanderschuren |first16=H. |last17=Zhang |first17=P.}}</ref><ref>{{cite web |date=2018 |title=BioCassava Plus |url=https://www.danforthcenter.org/scientists-research/research-institutes/institute-for-international-crop-improvement/crop-improvement-projects/biocassava-plus |archive-url=https://web.archive.org/web/20160327133605/http://www.danforthcenter.org/scientists-research/research-institutes/institute-for-international-crop-improvement/crop-improvement-projects/biocassava-plus |archive-date=27 March 2016 |access-date=23 March 2018 |publisher=Donald Danforth Plant Science Center |place=St. Louis, Missouri, USA}}</ref>

Raw cassava is 60% water, 38% carbohydrates, 1% protein, and has negligible [[fat]] (table).<ref name="fao">{{cite web |title=The Global Cassava Development Strategy|year=2004 |author=Tewe, Olumide O.|publisher=[[U.N. Food and Agriculture Organization]] |url=http://www.fao.org/docrep/007/j1255e/j1255e00.htm|access-date=24 November 2011|archive-date=19 January 2012|archive-url=https://web.archive.org/web/20120119045952/http://www.fao.org/docrep/007/j1255e/j1255e00.htm|url-status=live}}</ref> In a {{convert|100|g|oz|frac=2|abbr=off|adj=on}} reference serving, raw cassava provides {{convert|160|kcal|kJ|order=flip|abbr=off}} of [[food energy]] and 23% of the [[Daily Value]] (DV) of vitamin C, but otherwise has no [[micronutrients]] in significant content (i.e. above 10% of the relevant DV).<ref name="fao" />

Cassava has been studied as a feedstock to produce [[ethanol]] as a [[biofuel]], including to improve the efficiency of conversion from cassava flour,<ref name="Bakky 2021">{{cite journal |last1=Bakky |first1=Aa |last2=Hoque |first2=Mr |last3=Islam |first3=Ms |title=Production of Biofuel from Cassava |journal=Journal of Environmental Science and Natural Resources |volume=12 |issue=1–2 |date=11 February 2021 |issn=2408-8633 |doi=10.3329/jesnr.v12i1-2.52032 |pages=171–174}}</ref> and to convert crop residues such as stems and leaves as well as the more easily processed roots.<ref name="Sivamani 2018">{{cite journal |last1=Sivamani |first1=Selvaraju |last2=Chandrasekaran |first2=Arun Pandian |last3=Balajii |first3=Muthusamy |last4=Shanmugaprakash |first4=Muthusamy |last5=Hosseini-Bandegharaei |first5=Ahmad |last6=Baskar |first6=Rajoo |title=Evaluation of the potential of cassava-based residues for biofuels production |journal=Reviews in Environmental Science and Bio/Technology |volume=17 |issue=3 |date=2018 |issn=1569-1705 |doi=10.1007/s11157-018-9475-0 |pages=553–570|bibcode=2018RESBT..17..553S }}</ref> China has created facilities to produce substantial amounts of ethanol fuel from cassava roots.<ref name="CH15030">{{cite web |last1=Anderson-Sprecher |first1=Andrew |last2=Ji |first2=James |title=China Biofuel Industry Faces Uncertain Future |publisher=USDA Foreign Agriculture Service |url=https://apps.fas.usda.gov/newgainapi/api/report/downloadreportbyfilename?filename=Biofuels%20Annual_Beijing_China%20-%20Peoples%20Republic%20of_9-3-2015.pdf |access-date=8 November 2019 |archive-date=27 July 2020 |archive-url=https://web.archive.org/web/20200727083130/https://apps.fas.usda.gov/newgainapi/api/report/downloadreportbyfilename?filename=Biofuels%20Annual_Beijing_China%20-%20Peoples%20Republic%20of_9-3-2015.pdf |url-status=live }}</ref>

== Folklore ==

In Java, a myth relates that food derives from the body of Dewi Teknowati, who killed herself rather than accept the advances of the god [[Batara Guru]]. She was buried, and her lower leg grew into a cassava plant.<ref name="Sudardi Widyastuti 2016">{{cite journal |last1=Sudardi |first1=Bani |last2=Widyastuti |first2=Hesti |title=The Folklore about Food Sustainability according Javanese Culture |journal=Journal of Education and Social Science |issue=3 |year=2016 |pages=8–11 |url=https://www.jesoc.com/wp-content/uploads/2016/03/KC3_17.pdf}}</ref>

In Trinidad, folk stories tell of a ''saapina'' or snake-woman; the word is related to ''sabada'', meaning to pound, for what is traditionally a woman's work of pounding cassava.<ref name="Provost 2011">{{cite journal |last1=Provost |first1=M. C. L. |title=Where Asian Indian folklore meets Arawak and Kalinago folklore, 'Sound' Symmetry and Asymmetry can make you jump! |journal=Lokoratna Journal of Folklore |date=2011 |volume=6 |url=https://www.researchgate.net/publication/267155922}}</ref>

The identity of the [[Macushi]] people of Guyana is closely bound up with the growth and processing of cassava in their [[slash-and-burn]] subsistence lifestyle. A story tells that the great spirit Makunaima climbed a tree, cutting off pieces with his axe; when they landed on the ground, each piece became a type of animal. The opossum brought the people to the tree, where they found all the types of food, including bitter cassava. A bird told the people how to prepare the cassava safely.<ref name="Schacht Bell 2013">{{cite journal |last1=Schacht |first1=Ryan N. |title=Cassava and the Makushi: a shared history of resiliency and transformation" |journal=Food and Identity in the Caribbean |year=2013 |pages=15–29 |doi=10.5040/9781350042162.ch-001 |isbn=978-1-350-04216-2 |url=https://www.researchgate.net/publication/275521616}}</ref>

== See also ==

* [[Cassava-based dishes]]