Editing Monoculture (section)

=== Historic examples of genetic monocultures ===

==== Great Famine of Ireland ====
In Ireland, exclusive use of one variety of potato, the "lumper", led to the [[Great Famine (Ireland)|Great Famine]] of 1845–1849. Lumpers provided inexpensive food to feed the Irish masses. Potatoes were [[vegetative propagation|propagated vegetatively]] with little to no genetic variation. When ''[[Phytophthora infestans]]'' arrived in Ireland from the Americas in 1845, the lumper had no resistance to the disease, leading to the nearly complete failure of the potato crop across Ireland.

==== Bananas ====
Until the 1950s, the [[Gros Michel banana|Gros Michel]] cultivar of banana represented almost all bananas consumed in the United States because of their taste, small seeds, and efficiency to produce. Their small seeds, while more appealing than the large ones in other Asian cultivars, were not suitable for planting,<ref>{{Cite web|url=http://www.promusa.org/Gros+Michel|title=Gros Michel|website=The banana knowledge platform of the [[ProMusa]] network|access-date=2019-06-08}}</ref> meaning all new banana plants had to be grown from the cut [[Suckers (botany)|suckers]] of another plant. As a result of this [[Asexual reproduction|asexual]] form of planting, all bananas grown had identical genetic makeups which gave them no traits for resistance to ''[[Fusarium wilt]]'', a fungal disease that spread quickly throughout the Caribbean where they were being grown. By the beginning of the 1960s, growers had to switch to growing the [[Cavendish banana]], a cultivar grown in a similar way. This cultivar is under similar disease stress since all the bananas are clones of each other and could easily succumb as the Gros Michel did.<ref name=":16">{{Cite journal|last1=Schwarzacher|first1=Trude|last2=Heslop-Harrison|first2=J. S.|date=2007-10-01|title=Domestication, Genomics and the Future for Banana|url= |journal=[[Annals of Botany]]|volume=100|issue=5|pages=1073–1084|doi=10.1093/aob/mcm191|pmid=17766312|issn=0305-7364|pmc=2759213}}</ref>

==== Cattle ====
[[File:SOBREVVO EM RONDONIA DIA 07-08-2020 (FOTO BRUNO KELLY) (62) (50224604772).jpg|thumb|Aerial view of [[Deforestation of the Amazon rainforest|deforested area]] prepared for monoculture or [[Ranch|cattle ranching]], near Porto Velho in [[Rondônia]], Brazil, in 2020]] 
Genetic monoculture can also refer to a single breed of farm animal being raised in large-scale [[concentrated animal feeding operation]]s (CAFOs). Many [[Livestock|livestock production systems]] rely on just a small number of highly specialized breeds. Focusing heavily on a single trait (output) may come at the expense of other desirable traits{{Snd}}such as [[fecundity|fertility]], resistance to disease, [[wikt:|vigor]], and [[mothering]] instincts. In the early 1990s, a few [[Holstein cow|Holstein calves]] were observed to grow poorly and died in the first 6 months of life. They were all found to be [[homozygous]] for a mutation in the gene that caused bovine [[leukocyte adhesion deficiency]]. This mutation was found at a high frequency in Holstein populations worldwide. (15% among bulls in the US, 10% in Germany, and 16% in Japan.) Researchers studying the pedigrees of affected and carrier animals tracked the source of the mutation to a single bull that was widely used in livestock production. In 1990 there were approximately 4 million Holstein cattle in the US, making the affected population around 600,000 animals.<ref name=":17">{{cite news|url=http://albc-usa.etapwss.com/index.php/resources/internal/rare-breed-facts|title=The Value of Genome Mapping for the Genetic Conservation of Cattle|last=Williams|first=J.L.|date=2015-10-22|publisher=The [[Food and Agriculture Organization]] of the United Nations|access-date=2015-10-22|location=[[Rome]]|archive-url=https://web.archive.org/web/20160306175025/http://albc-usa.etapwss.com/index.php/resources/internal/rare-breed-facts|archive-date=6 March 2016|url-status=dead}}</ref>