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Selective breeding (also called artificial selection) is the process by which humans use
animal breeding Animal breeding is a branch of animal science Animal science (also bioscience) is described as "studying the biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Bioch ...
and
plant breeding Plant breeding is the science of changing the traits of plants Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy ...
to selectively develop particular
phenotypic trait A phenotypic trait, simply trait, or character state is a distinct variant of a phenotypic right , Here the relation between genotype and phenotype is illustrated, using a Punnett square, for the character of petal color in pea plants. Th ...
s (characteristics) by choosing which typically
animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells ...

animal
or
plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel ...

plant
males and females will
sexually reproduce Sex Sex is either of two divisions, typically male Male (♂) is the sex of an organism that produces the gamete known as sperm. A male gamete can fuse with a larger female gamete, or ovum, in the process of fertilization. A male cannot sexu ...
and have
offspring In biology, offspring are the young creation of living organisms, produced either by a Asexual reproduction, single organism or, in the case of sexual reproduction, two organisms. Collective offspring may be known as a brood or progeny in a more ...

offspring
together.
Domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another group to secure a more predictable supply of resources from that sec ...
animals are known as
breed A breed is a specific group of domestic animals having homogeneous appearance (phenotype), homogeneous behavior, and/or other characteristics that distinguish it from other organisms of the same species. In literature, there exist several slight ...
s, normally bred by a professional
breeder A breeder is a person who selectively breeds carefully selected mates Mates is an English surname, and may refer to: * James Mates (born 1964), British newsreader and journalist * Michael Mates (born 1934), British politician * Frederick S. Mat ...
, while domesticated plants are known as
varieties Variety may refer to: Science and technology Mathematics * Algebraic variety, the set of solutions of a system of polynomial equations * Variety (universal algebra), classes of algebraic structures defined by equations in universal algebra Hort ...
,
cultigen A cultigen (from the Latin ''cultus'' – cultivated, and ''gens'' – kind) or cultivated plant is a plant that has been deliberately altered or selected by humans; it is the result of artificial selection This Chihuahua (dog), Chihuahua mixed ...
s,
cultivar A cultivar is a type of plant that people have bred for desired traits, which are reproduced in each new generation by a method such as grafting, tissue culture or carefully controlled seed production. Most cultivars arise from purposeful human ...
s, or breeds. Two purebred animals of different breeds produce a
crossbreed A crossbreed is an organism with purebred Purebreds, also called purebreeds, are "" (''cultivars'') of an achieved through the process of . When the of a purebred animal is recorded, that animal is said to be '. True breeding In the world ...

crossbreed
, and crossbred plants are called hybrids. Flowers, vegetables and fruit-trees may be bred by amateurs and commercial or non-commercial professionals: major crops are usually the provenance of the professionals. In
animal breeding Animal breeding is a branch of animal science Animal science (also bioscience) is described as "studying the biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Bioch ...
, techniques such as
inbreeding Inbreeding is the production of offspring In biology, offspring are the young born of living organism, organisms, produced either by a single organism or, in the case of sexual reproduction, two organisms. Collective offspring may be known as ...
,
linebreeding Inbreeding is the production of offspring In biology, offspring are the young born of living organism, organisms, produced either by a single organism or, in the case of sexual reproduction, two organisms. Collective offspring may be known as ...
, and
outcrossing Out-crossing or out-breeding is the technique of crossing between different breeds. This is the practice of introducing unrelated genetic material into a breeding line. It increases genetic diversity, thus reducing the probability of an individua ...
are utilized. In
plant breeding Plant breeding is the science of changing the traits of plants Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy ...
, similar methods are used.
Charles Darwin Charles Robert Darwin (; ; 12 February 1809 – 19 April 1882) was an English naturalist Natural history is a domain of inquiry involving organism In biology, an organism () is any organic, life, living system that fu ...

Charles Darwin
discussed how selective breeding had been successful in producing change over time in his 1859 book, ''
On the Origin of Species ''On the Origin of Species'' (or, more completely, ''On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life''),The book's full original title was ''On the Origin of Species by Me ...
''. Its first chapter discusses selective breeding and
domestication Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another group to secure a more predictable supply of resources from that sec ...
of such animals as
pigeon Columbidae () is a bird family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain the well-being of its members and o ...

pigeon
s,
cat The cat (''Felis catus'') is a domestic Domestic may refer to: In the home * Anything relating to the human home A home, or domicile, is a space used as a permanent or semi-permanent residence for an individual, group or family ...

cat
s,
cattle Cattle, taurine cattle, Eurasian cattle, or European cattle (''Bos taurus'' or ''Bos primigenius taurus'') are large domestication, domesticated Cloven hoof, cloven-hooved herbivores. They are a prominent modern member of the subfamily Bovinae ...

cattle
, and
dog The dog or domestic dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a Domestication, domesticated descendant of the wolf which is characterized by an upturning tail. The dog Origin of the domestic dog, derived from an Pleistocene ...

dog
s. Darwin used artificial selection as a springboard to introduce and support the theory of
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype right , Here the relation between genotype and phenotype is illustrated, using a Punnett square, for the character of peta ...
. The deliberate exploitation of selective breeding to produce desired results has become very common in agriculture and experimental biology. Selective breeding can be unintentional, e.g., resulting from the process of human cultivation; and it may also produce unintended – desirable or undesirable – results. For example, in some grains, an increase in seed size may have resulted from certain ploughing practices rather than from the intentional selection of larger seeds. Most likely, there has been an interdependence between natural and artificial factors that have resulted in plant domestication.


History

Selective breeding of both plants and animals has been practiced since early
prehistory Prehistory, also known as pre-literary history, is the period of human history Human history, or world history, is the narrative of Human, humanity's past. It is understood through archaeology, anthropology, genetics, and linguistics, ...
; key species such as
wheat Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food. The many species of wheat together make up the genus ''Triticum''; the most widely grown is common wheat Common wheat (''Triticum aestivum'' ...

wheat
,
rice Rice is the seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was relea ...

rice
, and
dog The dog or domestic dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a Domestication, domesticated descendant of the wolf which is characterized by an upturning tail. The dog Origin of the domestic dog, derived from an Pleistocene ...

dog
s have been significantly different from their wild ancestors for millennia, and
maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It can also be ...

maize
, which required especially large changes from
teosinte ''Zea'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a spe ...

teosinte
, its wild form, was selectively bred in
Mesoamerica Mesoamerica is a historical and important region In geography, regions are areas that are broadly divided by physical characteristics (physical geography), human impact characteristics (human geography), and the interaction of humanity and the ...
. Selective breeding was practiced by the
Romans Roman or Romans usually refers to: *Rome , established_title = Founded , established_date = 753 BC , founder = King Romulus , image_map = Map of comune of Rome (metropolitan city of Capital Rome, region Lazio, ...
. Treatises as much as 2,000 years old give advice on selecting animals for different purposes, and these ancient works cite still older authorities, such as Mago the Carthaginian. The notion of selective breeding was later expressed by the
Persian Persian may refer to: * People and things from Iran, historically called ''Persia'' in the English language ** Persians, Persian people, the majority ethnic group in Iran, not to be conflated with the Iranian peoples ** Persian language, an Iranian ...

Persian
Muslim Muslims () are people who follow or practice Islam Islam (; ar, اَلْإِسْلَامُ, al-’Islām, "submission o God Oh God may refer to: * An exclamation; similar to "oh no", "oh yes", "oh my", "aw goodness", "ah gosh", ...

Muslim
polymath A polymath ( el, πολυμαθής, , "having learned much"; la, homo universalis, "universal human") is an individual whose knowledge spans a substantial number of subjects, known to draw on complex bodies of knowledge to solve specific prob ...

polymath
Abu Rayhan Biruni Abu Rayhan al-Biruni (973 – after 1050) was an Iranian peoples, Iranian in scholar and polymath during the Islamic Golden Age. He has been variously called as the "founder of Indology", "Father of Comparative religion, Comparative Religion ...
in the 11th century. He noted the idea in his book titled ''India'', which included various examples. Selective breeding was established as a scientific practice by Robert Bakewell during the
British Agricultural Revolution#REDIRECT British Agricultural Revolution#REDIRECT British Agricultural Revolution {{Redirect category shell, 1= {{R from other capitalisation ...
{{Redirect category shell, 1= {{R from other capitalisation ...
in the 18th century. Arguably, his most important breeding program was with sheep. Using native stock, he was able to quickly select for large, yet fine-boned sheep, with long, lustrous wool. The Lincoln Longwool was improved by Bakewell, and in turn the Lincoln was used to develop the subsequent breed, named the New (or Dishley) Leicester. It was hornless and had a square, meaty body with straight top lines. These sheep were exported widely, including to
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

Australia
and
North America North America is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continen ...

North America
, and have contributed to numerous modern breeds, despite the fact that they fell quickly out of favor as market preferences in meat and textiles changed. Bloodlines of these original New Leicesters survive today as the
English Leicester The Leicester Longwool is an England, English list of sheep breeds, breed of sheep. Alternative names for the breed include: Leicester, Bakewell Leicester, Dishley Leicester, English Leicester, Improved Leicester and New Leicester. It was origin ...
(or Leicester Longwool), which is primarily kept for wool production. Bakewell was also the first to breed cattle to be used primarily for beef. Previously, cattle were first and foremost kept for pulling
plough A plough or plow ( US; both ) is a farm tool for loosening or turning the soil before sowing Sowing is the process of planting. An area or object that has had seeds planted in it will be described as a sowed area. Plants which are usu ...

plough
s as
oxen An ox () (plural oxen, ), also known as a bullock (in BrE British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial ...

oxen
, but he crossed long-horned heifers and a Westmoreland bull to eventually create the Dishley Longhorn. As more and more farmers followed his lead, farm animals increased dramatically in size and quality. In 1700, the average weight of a
bull A bull is an intact (i.e., not castrated Castration (also known as orchiectomy or orchidectomy) is any action, surgical Surgery ''cheirourgikē'' (composed of χείρ, "hand", and ἔργον, "work"), via la, chirurgiae, meaning ...

bull
sold for slaughter was 370
pounds Pound or Pounds may refer to: Units * Pound (currency), a unit of currency * Pound sterling, the official currency of the United Kingdom * Pound (mass), a unit of mass * Pound (force), a unit of force * Rail pound, in rail profile Symbols * Po ...
(168 kg). By 1786, that weight had more than doubled to 840 pounds (381 kg). However, after his death, the Dishley Longhorn was replaced with short-horn versions. He also bred the Improved Black Cart horse, which later became the
Shire horse The Shire is a British breed of draught horse A draft horse (US), draught horse (UK) or dray horse (from the Old English ''dragan'' meaning "to draw or haul"; compare Dutch language, Dutch ''dragen'' and German language, German ''tragen' ...

Shire horse
.
Charles Darwin Charles Robert Darwin (; ; 12 February 1809 – 19 April 1882) was an English naturalist Natural history is a domain of inquiry involving organism In biology, an organism () is any organic, life, living system that fu ...

Charles Darwin
coined the term 'selective breeding'; he was interested in the process as an illustration of his proposed wider process of
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype right , Here the relation between genotype and phenotype is illustrated, using a Punnett square, for the character of peta ...
. Darwin noted that many domesticated animals and plants had special properties that were developed by intentional animal and
plant breeding Plant breeding is the science of changing the traits of plants Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy ...
from individuals that showed desirable characteristics, and discouraging the breeding of individuals with less desirable characteristics. Darwin used the term "artificial selection" twice in the 1859 first edition of his work ''
On the Origin of Species ''On the Origin of Species'' (or, more completely, ''On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life''),The book's full original title was ''On the Origin of Species by Me ...
'', in Chapter IV: Natural Selection, and in Chapter VI: Difficulties on Theory:


Animal breeding

Animals with homogeneous appearance, behavior, and other characteristics are known as particular breeds or pure breeds, and they are bred through
culling In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechan ...
animals with particular traits and selecting for further breeding those with other traits.
Purebred Purebreds, also called purebreeds, are "cultivated varieties" (''cultivars'') of an animal species achieved through the process of selective breeding. When the pedigree chart, lineage of a purebred animal is recorded, that animal is said to be ' ...
animals have a single, recognizable breed, and purebreds with recorded lineage are called
pedigree Pedigree may refer to: Breeding * Pedigree chart, a document to record ancestry, used by genealogists in study of human family lines, and in selective breeding of other animals ** Pedigree, a human genealogy (ancestry chart) ** Pedigree (animal) ...
d.
Crossbreed A crossbreed is an organism with purebred Purebreds, also called purebreeds, are "" (''cultivars'') of an achieved through the process of . When the of a purebred animal is recorded, that animal is said to be '. True breeding In the world ...

Crossbreed
s are a mix of two purebreds, whereas
mixed breed A mixed breed is a domesticated animal Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another group to secure a more predi ...
s are a mix of several breeds, often unknown. Animal breeding begins with breeding stock, a group of animals used for the purpose of planned breeding. When individuals are looking to breed animals, they look for certain valuable traits in purebred stock for a certain purpose, or may intend to use some type of
crossbreeding A crossbreed is an organism with purebred parents of two different breeds, varieties, or populations. ''Crossbreeding'', sometimes called "designer crossbreeding", is the process of breeding such an organism, While crossbreeding is used to main ...
to produce a new type of stock with different, and, it is presumed, superior abilities in a given area of endeavor. For example, to breed chickens, a breeder typically intends to receive eggs, meat, and new, young birds for further reproduction. Thus, the breeder has to study different breeds and types of chickens and analyze what can be expected from a certain set of characteristics before he or she starts breeding them. Therefore, when purchasing initial breeding stock, the breeder seeks a group of birds that will most closely fit the purpose intended. Purebred breeding aims to establish and maintain stable traits, that animals will pass to the next generation. By "breeding the best to the best," employing a certain degree of
inbreeding Inbreeding is the production of offspring In biology, offspring are the young born of living organism, organisms, produced either by a single organism or, in the case of sexual reproduction, two organisms. Collective offspring may be known as ...
, considerable culling, and selection for "superior" qualities, one could develop a bloodline superior in certain respects to the original base stock. Such animals can be recorded with a
breed registry A breed registry, also known as a herdbook, studbook or register, in animal husbandry Animal husbandry is the branch of agriculture concerned with animals that are raised for meat, animal fiber, fibre, milk, eggs, or other products. It includes d ...
, the organization that maintains
pedigree Pedigree may refer to: Breeding * Pedigree chart, a document to record ancestry, used by genealogists in study of human family lines, and in selective breeding of other animals ** Pedigree, a human genealogy (ancestry chart) ** Pedigree (animal) ...
s and/or
stud book A breed registry, also known as a herdbook, studbook or register, in animal husbandry Animal husbandry is the branch of agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key d ...
s. However, single-trait breeding, breeding for only one trait over all others, can be problematic. In one case mentioned by animal behaviorist
Temple Grandin Mary Temple Grandin (born August 29, 1947) is an American scientist and animal behaviorist. She is a prominent proponent for the humane treatment of livestock for slaughter and the author of more than 60 scientific papers on animal behavior. Gran ...
,
rooster The chicken (''Gallus gallus domesticus'') is a domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another ...

rooster
s bred for fast growth or heavy muscles did not know how to perform typical rooster courtship dances, which alienated the roosters from hens and led the roosters to kill the hens after mating with them. A Soviet attempt to breed lab rats with higher intelligence led to cases of neurosis severe enough to make the animals incapable of any problem solving unless drugs like
phenazepam Phenazepam (also known in Russia as bromdihydrochlorphenylbenzodiazepine) is a benzodiazepine drug, which was developed in the Soviet Union in 1975, and now produced in Russia and some Commonwealth of Independent States, CIS countries. Phenazepam ...

phenazepam
were used. The observable phenomenon of
hybrid vigor Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of any biological quality in a Hybrid (biology), hybrid offspring. An offspring is heterotic if its trait (biology), traits are enhanced as a result of mi ...
stands in contrast to the notion of breed purity. However, on the other hand, indiscriminate breeding of crossbred or
hybrid Hybrid may refer to: Economics and finance * Hybrid market, a system allowing stock trades to be completed either electronically or manually * Hybrid security, a type of economic instrument Technology Electrical power generation * Hybrid generato ...
animals may also result in degradation of quality. Studies in
evolutionary physiology Evolutionary physiology is the study of the biological evolution Evolution is change in the Heredity, heritable Phenotypic trait, characteristics of biological populations over successive generations. These characteristics are the Gene expre ...
, behavioral genetics, and other areas of organismal biology have also made use of deliberate selective breeding, though longer
generation timeIn population biology and demography, generation time is the average time between two consecutive generations in the lineages of a population In biology, a population is a number of all the organisms of the same group or species In bio ...

generation time
s and greater difficulty in breeding can make these projects challenging in such
vertebrates Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an indiv ...

vertebrates
as
house mice The house mouse (''Mus musculus'') is a small mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands ...
.
Garland A garland is a decorative braid, knot or wreath of flowers, leaves, or other material. Garlands can be worn on the head or around the neck, hung on an inanimate object, or laid in a place of cultural or religious importance. garlands on a Christma ...
T, Jr. (2003). Selection experiments: an under-utilized tool in biomechanics and organismal biology. Ch. 3, ''Vertebrate Biomechanics and Evolution'' ed. Bels VL, Gasc JP, Casinos A
PDF
/ref>
Garland A garland is a decorative braid, knot or wreath of flowers, leaves, or other material. Garlands can be worn on the head or around the neck, hung on an inanimate object, or laid in a place of cultural or religious importance. garlands on a Christma ...
T, Jr., Rose MR, eds. (2009)
''Experimental Evolution: Concepts, Methods, and Applications of Selection Experiments''.
University of California Press University of California Press, otherwise known as UC Press, is a publishing house Publishing is the activity of making information, literature, music, software and other content available to the public for sale or for free. Traditionally, t ...
, Berkeley, California.


Plant breeding

Plant breeding has been used for thousands of years, and began with the domestication of
wild Wild, wild or wild may refer to: Common meanings * Wild animal ''Wild Animal'' is the debut solo studio album by Canadian singer Vanity Vanity is the excessive belief in one's own abilities or attractiveness to others. Prior to the 14th centu ...
plants into uniform and predictable agricultural
cultigen A cultigen (from the Latin ''cultus'' – cultivated, and ''gens'' – kind) or cultivated plant is a plant that has been deliberately altered or selected by humans; it is the result of artificial selection This Chihuahua (dog), Chihuahua mixed ...
s. High-yielding varieties have been particularly important in agriculture. Selective plant breeding is also used in research to produce
transgenic A transgene is a gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance#History, Mendelian units of heredity..." (Greek language, Greek) meaning ''generation'' or ''birth'' ) ...
animals that breed "true" (i.e., are
homozygous Zygosity (the noun, zygote A zygote (from Greek ζυγωτός ''zygōtos'' "joined" or "yoked", from ζυγοῦν ''zygoun'' "to join" or "to yoke") is a eukaryotic cell formed by a fertilization event between two gamete A gamete ( /ˈ ...
) for artificially inserted or deleted genes.


Selective breeding in aquaculture

Selective breeding in aquaculture holds high potential for the genetic improvement of fish and shellfish. Unlike terrestrial livestock, the potential benefits of selective breeding in aquaculture were not realized until recently. This is because high mortality led to the selection of only a few broodstock, causing inbreeding depression, which then forced the use of wild broodstock. This was evident in selective breeding programs for growth rate, which resulted in slow growth and high mortality. Control of the reproduction cycle was one of the main reasons as it is a requisite for selective breeding programs. Artificial reproduction was not achieved because of the difficulties in hatching or feeding some farmed species such as eel and yellowtail farming. A suspected reason associated with the late realisation of success in selective breeding programs in aquaculture was the education of the concerned people – researchers, advisory personnel and fish farmers. The education of fish biologists paid less attention to quantitative genetics and breeding plans. Another was the failure of documentation of the genetic gains in successive generations. This in turn led to failure in quantifying economic benefits that successful selective breeding programs produce. Documentation of the genetic changes was considered important as they help in fine tuning further selection schemes.


Quality traits in aquaculture

Aquaculture species are reared for particular traits such as growth rate, survival rate, meat quality, resistance to diseases, age at sexual maturation, fecundity, shell traits like shell size, shell colour, etc. *Growth rate – growth rate is normally measured as either body weight or body length. This trait is of great economic importance for all aquaculture species as faster growth rate speeds up the turnover of production. Improved growth rates show that farmed animals utilize their feed more efficiently through a positive correlated response. *Survival rate – survival rate may take into account the degrees of resistance to diseases. This may also see the stress response as fish under stress are highly vulnerable to diseases. The stress fish experience could be of biological, chemical or environmental influence. *Meat quality – the quality of fish is of great economic importance in the market. Fish quality usually takes into account size, meatiness, and percentage of fat, colour of flesh, taste, shape of the body, ideal oil and omega-3 content. *Age at sexual maturation – The age of maturity in aquaculture species is another very important attribute for farmers as during early maturation the species divert all their energy to gonad production affecting growth and meat production and are more susceptible to health problems (Gjerde 1986). *Fecundity – As the fecundity in fish and shellfish is usually high it is not considered as a major trait for improvement. However, selective breeding practices may consider the size of the egg and correlate it with survival and early growth rate.


Finfish response to selection


Salmonids

Gjedrem (1979) showed that selection of Atlantic salmon (''Salmo salar'') led to an increase in body weight by 30% per generation. A comparative study on the performance of select Atlantic salmon with wild fish was conducted by AKVAFORSK Genetics Centre in Norway. The traits, for which the selection was done included growth rate, feed consumption, protein retention, energy retention, and feed conversion efficiency. Selected fish had a twice better growth rate, a 40% higher feed intake, and an increased protein and energy retention. This led to an overall 20% better Fed Conversion Efficiency as compared to the wild stock. Atlantic salmon have also been selected for resistance to bacterial and viral diseases. Selection was done to check resistance to Infectious Pancreatic Necrosis Virus (IPNV). The results showed 66.6% mortality for low-resistant species whereas the high-resistant species showed 29.3% mortality compared to wild species. Rainbow trout (''S. gairdneri'') was reported to show large improvements in growth rate after 7–10 generations of selection. Kincaid et al. (1977) showed that growth gains by 30% could be achieved by selectively breeding rainbow trout for three generations. A 7% increase in growth was recorded per generation for rainbow trout by Kause et al. (2005). In Japan, high resistance to IPNV in rainbow trout has been achieved by selectively breeding the stock. Resistant strains were found to have an average mortality of 4.3% whereas 96.1% mortality was observed in a highly sensitive strain. Coho salmon (''Oncorhynchus kisutch'') increase in weight was found to be more than 60% after four generations of selective breeding. In Chile, Neira et al. (2006) conducted experiments on early spawning dates in coho salmon. After selectively breeding the fish for four generations, spawning dates were 13–15 days earlier. Cyprinids Selective breeding programs for the Common carp (''Cyprinus carpio'') include improvement in growth, shape and resistance to disease. Experiments carried out in the USSR used crossings of broodstocks to increase genetic diversity and then selected the species for traits like growth rate, exterior traits and viability, and/or adaptation to environmental conditions like variations in temperature. Kirpichnikov ''et al.'' (1974) and Babouchkine (1987) selected carp for fast growth and tolerance to cold, the Ropsha carp. The results showed a 30–40% to 77.4% improvement of cold tolerance but did not provide any data for growth rate. An increase in growth rate was observed in the second generation in Vietnam. Moav and Wohlfarth (1976) showed positive results when selecting for slower growth for three generations compared to selecting for faster growth. Schaperclaus (1962) showed resistance to the dropsy disease wherein selected lines suffered low mortality (11.5%) compared to unselected (57%).


Channel Catfish

Growth was seen to increase by 12–20% in selectively bred ''Iictalurus punctatus''. More recently, the response of the Channel Catfish to selection for improved growth rate was found to be approximately 80%, i.e., an average of 13% per generation.


Shellfish response to selection


Oysters

Selection for live weight of Pacific oysters showed improvements ranging from 0.4% to 25.6% compared to the wild stock. Sydney-rock oysters (''Saccostrea commercialis'') showed a 4% increase after one generation and a 15% increase after two generations. Chilean oysters (''Ostrea chilensis''), selected for improvement in live weight and shell length showed a 10–13% gain in one generation. Bonamia ostrea is a protistan parasite that causes catastrophic losses (nearly 98%) in European flat oyster ''Ostrea edulis'' L. This protistan parasite is endemic to three oyster-regions in Europe. Selective breeding programs show that ''O. edulis'' susceptibility to the infection differs across oyster strains in Europe. A study carried out by Culloty et al. showed that ‘Rossmore' oysters in Cork harbour, Ireland had better resistance compared to other Irish strains. A selective breeding program at Cork harbour uses broodstock from 3– to 4-year-old survivors and is further controlled until a viable percentage reaches market size. Over the years ‘Rossmore' oysters have shown to develop lower prevalence of ''B. ostreae'' infection and percentage mortality. Ragone Calvo et al. (2003) selectively bred the eastern oyster, ''Crassostrea virginica'', for resistance against co-occurring parasites ''Haplosporidium nelson'' (MSX) and ''Perkinsus marinus'' (Dermo). They achieved dual resistance to the disease in four generations of selective breeding. The oysters showed higher growth and survival rates and low susceptibility to the infections. At the end of the experiment, artificially selected ''C. virginica'' showed a 34–48% higher survival rate.


Penaeid shrimps

Selection for growth in Penaeid shrimps yielded successful results. A selective breeding program for ''Litopenaeus stylirostris'' saw an 18% increase in growth after the fourth generation and 21% growth after the fifth generation. ''Marsupenaeus japonicas'' showed a 10.7% increase in growth after the first generation. Argue et al. (2002) conducted a selective breeding program on the Pacific White Shrimp,'' Litopenaeus vannamei'' at The Oceanic Institute, Waimanalo, USA from 1995 to 1998. They reported significant responses to selection compared to the unselected control shrimps. After one generation, a 21% increase was observed in growth and 18.4% increase in survival to TSV. The Taura Syndrome Virus (TSV) causes mortalities of 70% or more in shrimps. C.I. Oceanos S.A. in Colombia selected the survivors of the disease from infected ponds and used them as parents for the next generation. They achieved satisfying results in two or three generations wherein survival rates approached levels before the outbreak of the disease. The resulting heavy losses (up to 90%) caused by Infectious hypodermal and haematopoietic necrosis virus (IHHNV) caused a number of shrimp farming industries started to selectively breed shrimps resistant to this disease. Successful outcomes led to development of Super Shrimp, a selected line of ''L. stylirostris'' that is resistant to IHHNV infection. Tang et al. (2000) confirmed this by showing no mortalities in IHHNV- challenged Super Shrimp post larvae and juveniles.


Aquatic species versus terrestrial livestock

Selective breeding programs for aquatic species provide better outcomes compared to terrestrial livestock. This higher response to selection of aquatic farmed species can be attributed to the following: * High fecundity in both sexes fish and shellfish enabling higher selection intensity. * Large phenotypic and genetic variation in the selected traits. Selective breeding in aquaculture provide remarkable economic benefits to the industry, the primary one being that it reduces production costs due to faster turnover rates. This is because of faster growth rates, decreased maintenance rates, increased energy and protein retention, and better feed efficiency.Gjedrem, T & Baranski, M. (2009). ''Selective breeding in Aquaculture: An Introduction''. 1st Edition. Springer. Applying such genetic improvement program to aquaculture species will increase productivity to meet the increasing demands of growing populations.


Advantages and disadvantages

Selective breeding is a direct way to determine if a specific trait can evolve in response to selection. A single-generation method of breeding is not as accurate or direct. The process is also more practical and easier to understand than sibling analysis. Selective breeding is better for traits such as
physiology Physiology (; ) is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in the real world. ...
and behavior that are hard to measure because it requires fewer individuals to test than single-generation testing. However, there are disadvantages to this process. Because a single experiment done in selective breeding cannot be used to assess an entire group of genetic variances, individual experiments must be done for every individual trait. Also, because of the necessity of selective breeding experiments to require maintaining the organisms tested in a lab or
greenhouse A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of transparent material, such as glass, in which plant Plants are predominantly photosynthetic Photo ...

greenhouse
, it is impractical to use this breeding method on many organisms. Controlled mating instances are difficult to carry out in this case and this is a necessary component of selective breeding.


See also

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Animal breeding Animal breeding is a branch of animal science Animal science (also bioscience) is described as "studying the biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Bioch ...
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Animal husbandry Animal husbandry is the branch of agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Ex ...
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Breed registry A breed registry, also known as a herdbook, studbook or register, in animal husbandry Animal husbandry is the branch of agriculture concerned with animals that are raised for meat, animal fiber, fibre, milk, eggs, or other products. It includes d ...
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Breeding back Breeding back is a form of artificial selection This Chihuahua (dog), Chihuahua mixed-breed dog, mix and Great Dane shows the wide range of dog breed sizes created using selective breeding. Selective breeding (also called artificial selecti ...
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Captive breeding Captive breeding, also known as "captive propagation", is the process of maintaining plants or animals in controlled environments, such as wildlife reserves, zoo A zoo (short for zoological garden; also called an animal park or menagerie) is a fa ...
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Culling In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechan ...
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Eugenics Eugenics ( ; ) is a set of beliefs and practices that aim to improve the genetic quality of a human population Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedality, bipedalism ...
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Experimental evolution Experimental evolution is the use of laboratory experiments or controlled field manipulations to explore evolutionary dynamics. Evolution Evolution is change in the Heredity, heritable Phenotypic trait, characteristics of biological populati ...
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Gene pool The gene pool is the set of all genes, or genetic information, in any population, usually of a particular species. Description A large gene pool indicates extensive genetic diversity, which is associated with robust populations that can surviv ...
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Genetic engineering Genetic engineering, also called genetic modification or genetic manipulation, is the direct manipulation of an organism's gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_in ...
* Genomics of domestication *
Inbreeding Inbreeding is the production of offspring In biology, offspring are the young born of living organism, organisms, produced either by a single organism or, in the case of sexual reproduction, two organisms. Collective offspring may be known as ...
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Marker-assisted selection Marker assisted selection or marker aided selection (MAS) is an indirect selection process where a trait Trait may refer to: * Phenotypic trait in biology, which involve genes and characteristics of organisms * Trait (computer programming), a mod ...
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Mutation breeding Mutation breeding, sometimes referred to as "variation breeding", is the process of exposing seeds to chemicals or radiation in order to generate mutants with desirable traits to be bred with other cultivars. Plants created using mutagenesis are s ...
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Natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype right , Here the relation between genotype and phenotype is illustrated, using a Punnett square, for the character of peta ...
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Plant breeding Plant breeding is the science of changing the traits of plants Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy ...
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Serial passage Serial passage refers to the process of growing bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typ ...
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Quantitative genetics Quantitative genetics deals with phenotype right , Here the relation between genotype and phenotype is illustrated, using a Punnett square, for the character of petal color in pea plants. The letters B and b represent genes for color, and t ...
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Selection methods in plant breeding based on mode of reproduction Plant breeders use different methods depending on the mode of reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organism In biology, an organism (from Ancient Greek, Greek: ὀρ ...
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Smart breeding Marker assisted selection or marker aided selection (MAS) is an indirect selection process where a Trait (biology), trait of interest is selected based on a Biological marker, marker (Morphology (biology), morphological, biochemical or DNA/RNA vari ...


References


Bibliography

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Further reading


FAO. 2007. The Global Plan of Action for Animal Genetic Resources and the Interlaken Declaration. Rome.

FAO. 2015. The Second Report on the State of the World's Animal Genetic Resources for Food and Agriculture. Rome.
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External links



{{DEFAULTSORT:Selective Breeding Biotechnology Breeding, Selection