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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 that, through cellular respiration, can later be released to fuel t ...

plants
in order to produce desired characteristics. It has been used to improve the quality of nutrition in products for humans and animals. The goals of plant breeding are to produce crop varieties that boast unique and superior traits for a variety of agricultural applications. The most frequently addressed traits are those related to biotic and abiotic stress tolerance, grain or biomass yield, end-use quality characteristics such as taste or the concentrations of specific biological molecules (proteins, sugars, lipids, vitamins, fibers) and ease of processing (harvesting, milling, baking, malting, blending, etc.). Plant breeding can be performed through many different techniques ranging from simply selecting plants with desirable characteristics for propagation, to methods that make use of knowledge of genetics and chromosomes, to more complex molecular techniques (see
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. These plants, for the most part, have co ...
and
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 ...
). Genes in a plant are what determine what type of qualitative or quantitative traits it will have. Plant breeders strive to create a specific outcome of plants and potentially new plant varieties, and in the course of doing so, narrow down the genetic diversity of that variety to a specific few biotypes. It is practiced worldwide by individuals such as gardeners and farmers, and by professional plant breeders employed by organizations such as
government A government is the system or group of people governing an organized community, generally a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department ...

government
institutions, universities, crop-specific industry associations or research centers. International development agencies believe that breeding new crops is important for ensuring
food security Food security is the measure of the availability of food and individuals' Economic inequality, ability to access it. According to the United Nations' Committee on World Food Security, food security is defined as meaning that all people, at all ti ...
by developing new varieties that are higher yielding, disease resistant, drought tolerant or regionally adapted to different environments and growing conditions.


History

Plant breeding started with sedentary agriculture and particularly the domestication of the first
agricultural Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated Domestication is a sustained multi-generat ...

agricultural
plants, a practice which is estimated to date back 9,000 to 11,000 years. Initially early farmers simply selected food plants with particular desirable characteristics, and employed these as
progenitor In genealogy Genealogy (from el, γενεαλογία ' "study of family trees") is the study of Family, families, family history, and the tracing of their lineages. Genealogists use oral interviews, historical records, genetic analysis, an ...

progenitor
s for subsequent generations, resulting in an accumulation of valuable
trait Trait may refer to: * Phenotypic trait in biology, which involve genes and characteristics of organisms * Trait (computer programming), a model for structuring object-oriented programs (a template class in the C++ programming language) * Trait the ...
s over time.
Grafting Grafting or graftage is a horticultural Horticulture is the art of cultivating plants in gardens to produce food and medicinal ingredients, or for comfort and ornamental purposes. Horticulturists grow flowers, fruits and nuts, vegetables and h ...
technology had been practiced in China before 2000 BCE. By 500 BCE grafting was well established and practiced.
Gregor Mendel Gregor Johann Mendel (; cs, Řehoř Jan Mendel; 20 July 1822 – 6 January 1884) was a meteorologist, mathematician, biologist, AugustinianAugustinian may refer to: *Augustinians Augustinians are members of Christian religious orders tha ...

Gregor Mendel
(1822–84) is considered the "father of
genetics Genetics is a branch of 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, p ...

genetics
". His experiments with plant hybridization led to his establishing . Genetics stimulated research to improve crop production through plant breeding. Modern plant breeding is applied genetics, but its scientific basis is broader, covering
molecular biology Molecular biology is the branch of biology that seeks to understand the molecule, molecular basis of biological activity in and between Cell (biology), cells, including biomolecule, molecular synthesis, modification, mechanisms, and interactions ...
,
cytology Cell biology (also cellular biology or cytology) is a branch of biology studying the structure and function of the cell, also known as the basic unit of life Life is a characteristic that distinguishes physical entities that have bi ...
,
systematics Biological Biology is the natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), or ...
,
physiology Physiology (; ) is the scientific Science (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, know ...
,
pathology Pathology is the study of the causesCauses, or causality, is the relationship between one event and another. It may also refer to: * Causes (band), an indie band based in the Netherlands * Causes (company), an online company See also * Cau ...
,
entomology upright=1.2, A Phyllium sp., mimicking a leaf Entomology () is the scientific Science () is a systematic enterprise that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions abo ...
,
chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during a with other . ...

chemistry
, and
statistics Statistics is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data. In applying statistics to a scientific, industrial, or social problem, it is conventional to begin with a statistical ...

statistics
(
biometrics Biometrics are body measurements and calculations related to human characteristics. Biometrics authentication Authentication (from ''authentikos'', "real, genuine", from αὐθέντης ''authentes'', "author") is the act of proof (truth) ...

biometrics
). It has also developed its own technology.


Classical plant breeding

One major technique of plant breeding is selection, the process of selectively propagating plants with desirable characteristics and eliminating or "culling" those with less desirable characteristics. Another technique is the deliberate interbreeding (crossing) of closely or distantly related individuals to produce new crop varieties or lines with desirable properties. Plants are crossbred to introduce
traits Trait may refer to: * Phenotypic trait in biology, which involve genes and characteristics of organisms * Trait (computer programming), a model for structuring object-oriented programs (a template class in the C++ programming language) * Trait the ...
/
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'' ) is a basic unit of her ...

gene
s from one variety or line into a new genetic background. For example, a
mildew Mildew is a form of fungus A fungus (plural: fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. The ...
-resistant
pea The pea is most commonly the small spherical seed A seed is an embryonic plant enclosed in a protective outer covering. The formation of the seed is part of the process of reproduction Reproduction (or procreation or breeding) is ...

pea
may be crossed with a high-yielding but susceptible pea, the goal of the cross being to introduce mildew resistance without losing the high-yield characteristics. Progeny from the cross would then be crossed with the high-yielding parent to ensure that the progeny were most like the high-yielding parent, (
backcrossing Backcrossing is a crossing of a hybrid with one of its parent A parent is a caregiver of the offspring In biology, offspring are the young born of living organism, organisms, produced either by a single organism or, in the case of sexual repr ...

backcrossing
). The progeny from that cross would then be tested for yield (selection, as described above) and mildew resistance and high-yielding resistant plants would be further developed. Plants may also be crossed with themselves to produce inbred varieties for breeding. Pollinators may be excluded through the use of
pollination bagsPollination bags, sometimes called crossing bags, isolation bags or exclusion bags, are containers made of various different materials for the purpose of controlling pollination Pollination is the transfer of pollen Pollen Tube Diagram Pollen ...
. Classical breeding relies largely on
homologous recombination Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in Cell (biology), cellular organis ...

homologous recombination
between chromosomes to generate
genetic diversity Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species, it ranges widely from the number of species to differences within species In biology, a species is the basic unit of biological classificati ...
. The classical plant breeder may also make use of a number of ''in vitro'' techniques such as
protoplast fusion Somatic fusion, also called protoplast fusion, is a type of genetic modification in plants by which two distinct species of plants are fused together to form a new Hybrid (biology), hybrid plant with the characteristics of both, a somatic hybrid. ...
, embryo rescue or
mutagenesis Mutagenesis is a process by which the genetic information of an organism is changed by the production of a mutation. It may occur spontaneously in nature, or as a result of exposure to mutagens. It can also be achieved experimentally using laborat ...

mutagenesis
(see below) to generate diversity and produce hybrid plants that would not exist in
nature Nature, in the broadest sense, is the natural, physical, material world or universe The universe ( la, universus) is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and ...

nature
. Traits that breeders have tried to incorporate into crop plants include: # Improved
quality Quality may refer to: Concepts *Quality (business), the ''non-inferiority'' or ''superiority'' of something *Quality (philosophy), an attribute or a property *Quality (physics), in response theory *Energy quality, used in various science disciplin ...
, such as increased nutrition, improved flavor, or greater beauty # Increased
yield Yield may refer to: Measures of output/function Computer science * Yield (multithreading) is an action that occurs in a computer program during multithreading * See generator (computer programming) Physics/chemistry * Yield (chemistry), the amou ...
of the crop # Increased tolerance of environmental pressures (
salinity Salinity () is the saltiness or amount of dissolved in a body of , called (see also ). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal to ‰). Salinity is an important ...

salinity
, extreme
temperature Temperature ( ) is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy Thermal radiation in visible light can be seen on this hot metalwork. Thermal energy refers to several distinct physical concept ...

temperature
,
drought A drought is an event of prolonged shortages in the water supply, whether atmospheric (below-average precipitation In meteorology Meteorology is a branch of the atmospheric sciences Atmospheric science is the study of the Earth's atm ...

drought
) # Resistance to
virus A virus is a that only inside the living of an . Viruses infect all , from animals and plants to s, including and . Since 's 1892 article describing a non-bacterial infecting tobacco plants and the discovery of the by in 1898, more ...

virus
es,
fungi A fungus (plural: fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as ...

fungi
and
bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of all known organisms. Cells are the sm ...

bacteria
# Increased tolerance to
insect Insects (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Rom ...

insect
pests # Increased tolerance of
herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control unwanted plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, conv ...
s # Longer storage period for the harvested crop


Before World War II

Successful commercial plant breeding concerns were founded from the late 19th century. Gartons Agricultural Plant Breeders in England was established in the 1890s by John Garton, who was one of the first to commercialize new varieties of agricultural crops created through cross-pollination. The firm's first introduction was Abundance
Oat The oat (''Avena sativa''), sometimes called the common oat, is a of grown for its seed, which is known by the same name (usually in the plural, unlike other cereals and ). While oats are suitable for human consumption as and , one of the m ...
, one of the first agricultural grain varieties bred from a ''controlled'' cross, introduced to commerce in 1892. In the early 20th century, plant breeders realized that findings on the non-random nature of
inheritance Inheritance is the practice of passing on private property Private property is a legal designation for the ownership of property by non-governmental legal entities. Private property is distinguishable from public property Public property i ...

inheritance
could be applied to
seedling A seedling is a young sporophyte '' Tortula muralis''. In mosses, the gametophyte is the dominant generation, while the sporophytes consist of sporangium-bearing stalks growing from the tips of the gametophytes A sporophyte () is the dip ...

seedling
populations produced through deliberate
pollination Pollination is the transfer of pollen from an anther (male part) of a plant to the stigma (female part) of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by Anemophily, wind. Pollinating agents are a ...

pollination
s to predict the frequencies of different types. Wheat hybrids were bred to increase the crop production of
Italy Italy ( it, Italia ), officially the Italian Republic ( it, Repubblica Italiana, links=no ), is a country consisting of Italian Peninsula, a peninsula delimited by the Alps and List of islands of Italy, several islands surrounding it, whose ...

Italy
during the so-called "
Battle for Grain The Battle for Grain was an economic policy undertaken by the Fascists in Italy Italy ( it, Italia ), officially the Italian Republic ( it, Repubblica Italiana, links=no ), is a country consisting of a Northern Italy, continental part, del ...
" (1925–1940).
Heterosis Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of any biological quality in a hybrid Hybrid may refer to: Economics and finance * Hybrid market, a system allowing stock trades to be completed either ...

Heterosis
was explained by
George Harrison Shull George Harrison Shull (April 15, 1874 – September 28, 1954) was an eminent American plant geneticist A geneticist is a biologist who studies genetics, the science of genes, heredity, and variation of organism In biology, an organism ...
. It describes the tendency of the progeny of a specific cross to outperform both parents. The detection of the usefulness of heterosis for plant breeding has led to the development of inbred lines that reveal a heterotic yield advantage when they are crossed.
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
was the first species where heterosis was widely used to produce hybrids.
Statistical Statistics is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data Data are units of information Information can be thought of as the resolution of uncertainty; it answers th ...

Statistical
methods were also developed to analyze gene action and distinguish heritable variation from variation caused by environment. In 1933 another important breeding technique, cytoplasmic male sterility (CMS), developed in maize, was described by Marcus Morton Rhoades. CMS is a maternally inherited trait that makes the plant produce sterile
pollen Pollen is a powdery substance consisting of pollen grains which are microsporophytes of seed plants The spermatophytes (; ), also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plant Plant ...

pollen
. This enables the production of hybrids without the need for labor-intensive detasseling. These early breeding techniques resulted in large yield increase in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

United States
in the early 20th century. Similar yield increases were not produced elsewhere until after
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a global war A world war is "a war War is an intense armed conflict between states State may refer to: Arts, entertainment, and media Literatur ...
, the
Green Revolution The Green Revolution, or the Third Agricultural Revolution (after the Neolithic Revolution The Neolithic Revolution, or the (First) Agricultural Revolution, was the wide-scale transition of many human culture Culture () is an umbrel ...

Green Revolution
increased crop production in the developing world in the 1960s.


After World War II

Following
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a global war A world war is "a war War is an intense armed conflict between states State may refer to: Arts, entertainment, and media Literatur ...
a number of techniques were developed that allowed plant breeders to hybridize distantly related species, and artificially induce genetic diversity. When distantly related species are crossed, plant breeders make use of a number of
plant tissue culture Plant tissue culture is a collection of techniques used to maintain or grow plant cells, tissues or organs under sterile conditions on a nutrient culture medium of known composition. It is widely used to produce clones of a plant in a method known ...
techniques to produce progeny from otherwise fruitless mating. Interspecific and intergeneric hybrids are produced from a cross of related species or genera that do not normally
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 ...

sexually reproduce
with each other. These crosses are referred to as ''Wide crosses''. For example, the
cereal A cereal is any Poaceae, grass cultivated (grown) for the edible components of its grain (botanically, a type of fruit called a caryopsis), composed of the endosperm, cereal germ, germ, and bran. The term may also refer to the resulting grain ...

cereal
triticale Triticale (; × ''Triticosecale'') is a 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 Techno ...

triticale
is a
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
and
rye Rye (''Secale cereale'') is a grass Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants known as grasses. It includes the cereal grasses, bamboo Bamboos are a diverse group of ev ...

rye
hybrid. The cells in the plants derived from the first generation created from the cross contained an uneven number of chromosomes and as a result was sterile. The
cell division Cell division is the process by which a parent cell (biology), cell divides into two or more daughter cells. Cell division usually occurs as part of a larger cell cycle. In eukaryotes, there are two distinct types of cell division; a vegetative ...

cell division
inhibitor
colchicine Colchicine is a medication used to treat gout Gout is a form of inflammatory arthritisInflammatory arthritis is a group of diseases which includes: rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that ...

colchicine
was used to double the number of
chromosome A chromosome is a long DNA molecule with part or all of the genome, genetic material of an organism. Most eukaryotic chromosomes include packaging proteins called histones which, aided by Chaperone (protein), chaperone proteins, bind to and ...

chromosome
s in the cell and thus allow the production of a fertile line. Failure to produce a hybrid may be due to pre- or post-
fertilization Fertilisation or fertilization (see American and British English spelling differences#-ise.2C -ize .28-isation.2C -ization.29, spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes ...

fertilization
incompatibility. If fertilization is possible between two species or genera, the hybrid
embryo An embryo is the early stage of development of a multicellular organism A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms ar ...

embryo
may abort before maturation. If this does occur the embryo resulting from an interspecific or intergeneric cross can sometimes be rescued and cultured to produce a whole plant. Such a method is referred to as Embryo Rescue. This technique has been used to produce new rice for Africa, an interspecific cross of Asian rice ''(Oryza sativa)'' and
African rice ''Oryza glaberrima'', commonly known as African rice, is one of the two domesticated rice species. It was first domesticated and grown in West Africa around 3,000 years ago. It is now rarely sold in West African markets, having been replaced by As ...
''(Oryza glaberrima)''. Hybrids may also be produced by a technique called
protoplast Protoplast, from ancient Greek (''prōtóplastos'', "first-formed"), is a biology, biological term coined by Johannes von Hanstein, Hanstein in 1880 to refer to the entire cell, excluding the cell wall. Protoplasts can be generated by strippin ...
fusion. In this case protoplasts are fused, usually in an electric field. Viable recombinants can be regenerated in culture. Chemical
mutagen In genetics, a mutagen is a physical or chemical agent that permanently changes genetic material, usually DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pent ...
s like
EMS#REDIRECT EMS Ems or EMS may refer to: Places and rivers * Domat/Ems Domat/Ems ( rm, Domat ; german: Ems) is a municipality A municipality is usually a single administrative division having Municipal corporation, corporate status and powe ...

EMS
and ,
radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and f ...

radiation
and
transposon A transposable element (TE, transposon, or jumping gene) is a DNA sequence DNA sequencing is the process of determining the nucleic acid sequence A nucleic acid sequence is a succession of bases signified by a series of a set of five diff ...
s are used to generate
mutant 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 ...

mutant
s with desirable traits to be bred with other
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 – a process known as ''Mutation Breeding''. Classical plant breeders also generate genetic diversity within a species by exploiting a process called somaclonal variation, which occurs in plants produced from tissue culture, particularly plants derived from
callus A callus is an area of thickened skin that forms as a response to repeated friction, pressure, or other irritation. Since repeated contact is required, calluses are most often found on the feet and hands, but they may occur anywhere on the ski ...
. Induced
polyploidy Polyploidy is a condition in which the cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or religious recluse ...
, and the addition or removal of chromosomes using a technique called chromosome engineering may also be used. When a desirable trait has been bred into a species, a number of crosses to the favored parent are made to make the new plant as similar to the favored parent as possible. Returning to the example of the mildew resistant pea being crossed with a high-yielding but susceptible pea, to make the mildew resistant progeny of the cross most like the high-yielding parent, the progeny will be crossed back to that parent for several generations (See
backcrossing Backcrossing is a crossing of a hybrid with one of its parent A parent is a caregiver of the offspring In biology, offspring are the young born of living organism, organisms, produced either by a single organism or, in the case of sexual repr ...

backcrossing
). This process removes most of the genetic contribution of the mildew resistant parent. Classical breeding is therefore a cyclical process. With classical breeding techniques, the breeder does not know exactly what genes have been introduced to the new cultivars. Some
scientist A scientist is a person who conducts scientific research The scientific method is an Empirical evidence, empirical method of acquiring knowledge that has characterized the development of science since at least the 17th century. It involves ...

scientist
s therefore argue that plants produced by classical breeding methods should undergo the same safety testing regime as
genetically modified 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 ...
plants. There have been instances where plants bred using classical techniques have been unsuitable for human consumption, for example the
poison In biology, poisons are Chemical substance, substances that can cause death, injury or harm to organs, Tissue (biology), tissues, Cell (biology), cells, and DNA usually by chemical reactions or other activity (chemistry), activity on the molecul ...

poison
solanine Solanine is a glycoalkaloid poison found in species of the Solanaceae, nightshade family within the genus ''Solanum'', such as the potato (''Solanum tuberosum''), the tomato (''Solanum lycopersicum''), and the eggplant (''Solanum melongena''). I ...

solanine
was unintentionally increased to unacceptable levels in certain varieties of
potato The potato is a starch#Food, starchy tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial plant, perennial in the nightshade family Solanaceae. Wild potato species can be found thro ...

potato
through plant breeding. New potato varieties are often screened for solanine levels before reaching the marketplace. Even with the very latest in
biotech Biotechnology is a broad area of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physi ...
-assisted conventional breeding, incorporation of a
trait Trait may refer to: * Phenotypic trait in biology, which involve genes and characteristics of organisms * Trait (computer programming), a model for structuring object-oriented programs (a template class in the C++ programming language) * Trait the ...
takes an average of seven
generation A generation is "all of the people born and living Living or The Living may refer to: Common meanings *Life, a condition that distinguishes organisms from inorganic objects and dead organisms ** extant taxon, Living species, one that is not ex ...

generation
s for clonally propagated crops, nine for self-fertilising, and seventeen for cross-pollinating.


Modern plant breeding

Modern plant breeding may use techniques of molecular biology to select, or in the case of genetic modification, to insert, desirable traits into plants. Application of biotechnology or molecular biology is also known as molecular breeding.


Marker assisted selection

Sometimes many different genes can influence a desirable trait in plant breeding. The use of tools such as molecular markers or DNA fingerprinting can map thousands of genes. This allows plant breeders to screen large populations of plants for those that possess the trait of interest. The screening is based on the presence or absence of a certain gene as determined by laboratory procedures, rather than on the visual identification of the expressed trait in the plant. The purpose of marker assisted selection, or plant genome analysis, is to identify the location and function (phenotype) of various genes within the genome. If all of the genes are identified it leads to genome sequence. All plants have varying sizes and lengths of genomes with genes that code for different proteins, but many are also the same. If a gene's location and function is identified in one plant species, a very similar gene likely can also be found in a similar location in another related species genome.


Reverse breeding and doubled haploids (DH)

Homozygous plants with desirable traits can be produced from heterozygous starting plants, if a haploid cell with the alleles for those traits can be produced, and then used to make a Doubled haploidy, doubled haploid. The doubled haploid will be homozygous for the desired traits. Furthermore, two different homozygous plants created in that way can be used to produce a generation of F1 hybrid plants which have the advantages of heterozygosity and a greater range of possible traits. Thus, an individual heterozygous plant chosen for its desirable characteristics can be converted into a heterozygous variety (F1 hybrid) without the necessity of vegetative reproduction but as the result of the cross of two homozygous/doubled haploid lines derived from the originally selected plant. Plant tissue culturing can produce haploid or double haploid plant lines and generations. This cuts down the genetic diversity taken from that plant species in order to select for desirable traits that will increase the fitness of the individuals. Using this method decreases the need for breeding multiple generations of plants to get a generation that is homogenous for the desired traits, thereby saving much time over the natural version of the same process. There are many plant tissue culturing techniques that can be used to achieve haploid plants, but microspore culturing is currently the most promising for producing the largest numbers of them.


Genetic modification

Genetic modification of plants is achieved by adding a specific gene or genes to a plant, or by knocking down a gene with RNAi, to produce a desirable phenotype. The plants resulting from adding a gene are often referred to as transgenic plants. If for genetic modification genes of the species or of a crossable plant are used under control of their native promoter, then they are called cisgenesis, cisgenic plants. Sometimes genetic modification can produce a plant with the desired trait or traits faster than classical breeding because the majority of the plant's genome is not altered. To genetically modify a plant, a genetic construct must be designed so that the gene to be added or removed will be expressed by the plant. To do this, a promoter (biology), promoter to drive Transcription (genetics), transcription and a termination sequence to stop transcription of the new gene, and the gene or genes of interest must be introduced to the plant. A marker for the selection of transformed plants is also included. In the laboratory, antibiotic resistance is a commonly used marker: Plants that have been successfully transformed will grow on media containing antibiotics; plants that have not been transformed will die. In some instances markers for selection are removed by
backcrossing Backcrossing is a crossing of a hybrid with one of its parent A parent is a caregiver of the offspring In biology, offspring are the young born of living organism, organisms, produced either by a single organism or, in the case of sexual repr ...

backcrossing
with the parent plant prior to commercial release. The construct can be inserted in the plant genome by genetic recombination using the bacteria ''Agrobacterium tumefaciens'' or ''Agrobacterium rhizogenes, A. rhizogenes'', or by direct methods like the gene gun or microinjection. Using plant
virus A virus is a that only inside the living of an . Viruses infect all , from animals and plants to s, including and . Since 's 1892 article describing a non-bacterial infecting tobacco plants and the discovery of the by in 1898, more ...

virus
es to insert genetic constructs into plants is also a possibility, but the technique is limited by the host range of the virus. For example, Cauliflower mosaic virus (CaMV) only infects cauliflower and related species. Another limitation of viral vectors is that the virus is not usually passed on to the progeny, so every plant has to be inoculated. The majority of commercially released transgenic plants are currently limited to plants that have introduced resistance to
insect Insects (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Rom ...

insect
pest (animal), pests and
herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control unwanted plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, conv ...
s. Insect resistance is achieved through incorporation of a gene from ''Bacillus thuringiensis'' (Bt) that encodes a protein that is toxic to some insects. For example, the Helicoverpa zea, cotton bollworm, a common cotton pest, feeds on Bt cotton it will ingest the toxin and die. Herbicides usually work by binding to certain plant enzymes and inhibiting their action. The enzymes that the herbicide inhibits are known as the herbicides ''target site''. Herbicide resistance can be engineered into crops by expressing a version of ''target site'' protein that is not inhibited by the herbicide. This is the method used to produce glyphosate resistant ("Roundup Ready") crop plants. Genetic modification can further increase yields by increasing stress tolerance to a given environment. Stresses such as temperature variation, are signalled to the plant via a cascade of signalling molecules which will activate a transcription factor to regulate gene expression. Overexpression of particular genes involved in cold acclimation has been shown to produce more resistance to freezing, which is one common cause of yield loss Genetic modification of plants that can produce pharmaceuticals (and industrial chemicals), sometimes called ''pharming (genetics), pharming'', is a rather radical new area of plant breeding.


Breeding and the microbiome

Microbiomes of breeding lines showed that hybrid plants share much of their bacterial community with their parents, such as Cucurbita seeds and apple shoot endophytes. In addition, the proportional contribution of the microbiome from parents to offspring corresponds to the amount of genetic material contributed by each parent during breeding and domestication.


Phenotyping and artificial intelligence

machine learning and especially deep learning, deep machine learning has recently become more commonly used in phenotyping. Computer vision using ML has made great strides and is now being applied to leaf phenotyping and other phenotyping jobs typically performed by human eyes. Pound et al 2017 and Singh et al 2016 are especially salient examples of early successful application and demonstration of the general usability of the process across ''multiple'' target plant species. These methods will work even better with large, publicly available open data sets.


Speed breeding

Speed breeding is introduced by Watson et al 2018. Classical (human performed) phenotyping ''during'' speed breeding is also possible, using a procedure developed by Richard et al 2015. it is highly anticipated that SB and automated phenotyping will, combined, produce greatly improved outcomes see above.


Issues and concerns

Modern plant breeding, whether classical or through genetic engineering, comes with issues of concern, particularly with regard to food crops. The question of whether breeding can have a negative effect on nutritional value is central in this respect. Although relatively little direct research in this area has been done, there are scientific indications that, by favoring certain aspects of a plant's development, other aspects may be retarded. A study published in the ''Journal of the American College of Nutrition'' in 2004, entitled ''Changes in USDA Food Composition Data for 43 Garden Crops, 1950 to 1999'', compared nutritional analysis of vegetables done in 1950 and in 1999, and found substantial decreases in six of 13 nutrients measured, including 6% of protein and 38% of riboflavin. Reductions in calcium, phosphorus, iron and ascorbic acid were also found. The study, conducted at the Biochemical Institute, University of Texas at Austin, concluded in summary: ''"We suggest that any real declines are generally most easily explained by changes in cultivated varieties between 1950 and 1999, in which there may be trade-offs between
yield Yield may refer to: Measures of output/function Computer science * Yield (multithreading) is an action that occurs in a computer program during multithreading * See generator (computer programming) Physics/chemistry * Yield (chemistry), the amou ...
and nutrient content."'' The debate surrounding genetically modified food during the 1990s peaked in 1999 in terms of media coverage and risk perception, and continues today – for example, "''Germany has thrown its weight behind a growing European mutiny over genetically modified crops by banning the planting of a widely grown pest-resistant corn variety.''" The debate encompasses the Ecological impact of transgenic plants, ecological impact of genetically modified plants, the safety of genetically modified food and concepts used for safety evaluation like substantial equivalence. Such concerns are not new to plant breeding. Most countries have regulatory processes in place to help ensure that new crop varieties entering the marketplace are both safe and meet farmers' needs. Examples include variety registration, seed schemes, regulatory authorizations for GM plants, etc. Plant breeders' rights is also a major and controversial issue. Today, production of new varieties is dominated by commercial plant breeders, who seek to protect their work and collect royalties through national and international agreements based in intellectual property rights. The range of related issues is complex. In the simplest terms, critics of the increasingly restrictive regulations argue that, through a combination of technical and economic pressures, commercial breeders are reducing biodiversity and significantly constraining individuals (such as farmers) from developing and trading seed on a regional level. Efforts to strengthen breeders' rights, for example, by lengthening periods of variety protection, are ongoing. When new plant breeds or cultivars are bred, they must be maintained and propagated. Some plants are propagated by asexual means while others are propagated by seeds. Seed propagated cultivars require specific control over seed source and production procedures to maintain the integrity of the plant breeds results. Isolation is necessary to prevent cross contamination with related plants or the mixing of seeds after harvesting. Isolation is normally accomplished by planting distance but in certain crops, plants are enclosed in greenhouses or cages (most commonly used when producing F1 hybrids). Breeding is also not a quick process. This is especially important when breeding to ameliorate a disease: The average time from human recognition of a new fungal disease threat to the release of a resistant crop for that pathogen is at least twelve years.


Role of plant breeding in organic agriculture

Critics of organic agriculture claim it is too low-yielding to be a viable alternative to conventional agriculture. However, part of that poor performance may be the result of growing poorly adapted varieties. It is estimated that over 95% of organic agriculture is based on conventionally adapted varieties, even though the production environments found in organic vs. conventional farming systems are vastly different due to their distinctive management practices. Most notably, organic farmers have fewer inputs available than conventional growers to control their production environments. Breeding varieties specifically adapted to the unique conditions of organic agriculture is critical for this sector to realize its full potential. This requires selection for traits such as: * Water use efficiency * Nutrient use efficiency (particularly nitrogen and phosphorus) * Weed competitiveness * Tolerance of mechanical weed control * Pest/disease resistance * Early maturity (as a mechanism for avoidance of particular stresses) * Abiotic stress tolerance (i.e. drought, salinity, etc...) Currently, few breeding programs are directed at organic agriculture and until recently those that did address this sector have generally relied on indirect selection (i.e. selection in conventional environments for traits considered important for organic agriculture). However, because the difference between organic and conventional environments is large, a given genotype may perform very differently in each environment due to an interaction between genes and the environment (see gene–environment interaction). If this interaction is severe enough, an important trait required for the organic environment may not be revealed in the conventional environment, which can result in the selection of poorly adapted individuals. To ensure the most adapted varieties are identified, advocates of organic breeding now promote the use of direct selection (i.e. selection in the target environment) for many agronomic traits. There are many classical and modern breeding techniques that can be utilized for crop improvement in organic agriculture despite the ban on genetically modified organisms. For instance, controlled crosses between individuals allow desirable genetic variation to be recombined and transferred to seed progeny via natural processes. Marker assisted selection can also be employed as a diagnostics tool to facilitate selection of progeny who possess the desired trait(s), greatly speeding up the breeding process. This technique has proven particularly useful for the introgression of resistance genes into new backgrounds, as well as the efficient selection of many resistance genes pyramided into a single individual. Unfortunately, molecular markers are not currently available for many important traits, especially complex ones controlled by many genes.


Breeding and food security

For agriculture to thrive in the future, changes must be made to address arising global issues. These issues are the lack of arable land, increasingly harsh cropping conditions and the need to maintain food security, which involves being able to provide the world population with sufficient nutrition. Crops need to be able to mature in multiple environments to allow worldwide access, which involves solving problems including drought tolerance. It has been suggested that global solutions are achievable through the process of plant breeding, with its ability to select specific genes allowing crops to perform at a level which yields the desired results.


Yield

With an increasing population, the production of food needs to increase with it. It is estimated that a 70% increase in food production is needed by 2050 in order to meet the Declaration of the World Summit on Food Security. But with the degradation of agricultural land, simply planting more crops is no longer a viable option. New varieties of plants can in some cases be developed through plant breeding that generate an increase of yield without relying on an increase in land area. An example of this can be seen in Asia, where food production per capita has increased twofold. This has been achieved through not only the use of fertilisers, but through the use of better crops that have been specifically designed for the area.


Nutritional value

Plant breeding can contribute to global food security as it is a cost-effective tool for increasing nutritional value of forage and crops. Improvements in nutritional value for forage crops from the use of analytical chemistry and rumen fermentation technology have been recorded since 1960; this science and technology gave breeders the ability to screen thousands of samples within a small amount of time, meaning breeders could identify a high performing hybrid quicker. The genetic improvement was mainly in vitro dry matter digestibility (IVDMD) resulting in 0.7-2.5% increase, at just 1% increase in IVDMD a single Bos Taurus also known as beef cattle reported 3.2% increase in daily gains. This improvement indicates plant breeding is an essential tool in gearing future agriculture to perform at a more advanced level.


Environmental stressors

Plant breeding of hybrid crops has become extremely popular worldwide in an effort to combat the harsh environment. With long periods of drought and lack of water or nitrogen stress tolerance has become a significant part of agriculture. Plant breeders have focused on identifying crops which will ensure crops perform under these conditions; a way to achieve this is finding strains of the crop that is resistance to drought conditions with low nitrogen. It is evident from this that plant breeding is vital for future agriculture to survive as it enables farmers to produce stress resistant crops hence improving food security. In countries that experience harsh winters such as Iceland, Germany and further east in Europe, plant breeders are involved in breeding for tolerance to frost, continuous snow-cover, frost-drought (desiccation from wind and solar radiation under frost) and high moisture levels in soil in winter.


Participatory plant breeding

Participatory plant breeding (PPB) is when farmers are involved in a crop improvement programme with opportunities to make decisions and contribute to the research process at different stages. Participatory approaches to crop improvement can also be applied when plant biotechnologies are being used for crop improvement. Local agricultural systems and genetic diversity are developed and strengthened by crop improvement, which participatory crop improvement (PCI) plays a large role. PPB is enhanced by farmers knowledge of the quality required and evaluation of target environment which affects the effectiveness of PPB.


List of notable plant breeders

* Thomas Andrew Knight * Keith Downey (agricultural scientist), Keith Downey * Luther Burbank * Nazareno Strampelli * Niels Ebbesen Hansen * Norman Borlaug


See also

* Bioactive compound * Cisgenesis * Crop * Crop breeding in Nepal * Cultivated plant taxonomy * Double-pair mating * EUCARPIA * Family based QTL mapping * Genomics of domestication * International Code of Nomenclature for Cultivated Plants * Marker assisted selection, Marker-assisted selection (MAS) * Orthodox seed * QTL mapping * Recalcitrant seed * Selection methods in plant breeding based on mode of reproduction * Smart breeding * Composite cross population * Bioprospecting, Bioprospecting / biopiracy / Access and Benefit Sharing Agreement * Plant Treaty / Convention on Biological Diversity and Nagoya Protocol * International Convention for the Protection of New Varieties of Plants, UPOV Convention on New Varieties of Plants * Farmers rights / Peasants' rights * Genetic resources (disambiguation)


References


General

* * Briggs, F.N. and Knowles, P.F. 1967. ''Introduction to Plant Breeding''. Reinhold Publishing Corporation, New York. * Curry, Helen Anne. ''Evolution Made to Order: Plant Breeding and Technological Innovation in Twentieth-Century America'' (U of Chicago Press, 2016). x, 285 pp. * *
The Origins of Agriculture and Crop Domestication – The Harlan Symposium
' * Schlegel, Rolf (2009
Encyclopedic Dictionary of Plant Breeding
2nd ed. (), CRC Press, Boca Raton, FL, USA, pp 584 * Schlegel, Rolf (2007
Concise Encyclopedia of Crop Improvement: Institutions, Persons, Theories, Methods, and Histories
(), CRC Press, Boca Raton, FL, USA, pp 423 * Schlegel, Rolf (2014) Dictionary of Plant Breeding, 2nd ed., (), CRC Press, Boca Raton, Taylor & Francis Group, Inc., New York, USA, pp 584 * * * * Thro, A.M.; Spillane, C. (1999
Biotechnology assisted participatory plant breeding: Complement or contradiction?
CGIAR Program on Participatory Research and Gender Analysis, Working Document No.4, CIAT: Cali. 150pp. * *


External links


Plant Breeding and Genomics eXtension Community of Practice
– education and training materials for plant breeders and allied professionals
Plant Breeding Updates

Hybridization of Crop Plants
– large practical reference on plant hybridization


Glossary of plant breeding terminology by the Open Plant Breeding Foundation

National Association of Plant Breeders (NAPB)

The Global Partnership Initiative for Plant Breeding Capacity Building – GIPB

FAO/IAEA Programme Mutant Variety Database


*[https://www.vermontlaw.edu/sites/default/files/2020-01/Defensive-Publication-Guide.pdf A Breed Apart: The Plant Breeder's Guide to Preventing Patents through Defensive Publication] by Cydnee V. Bence & Emily J. Speigel, 2019 {{Authority control Plant breeding, Agronomy, Breeding Molecular biology Plant reproduction, Breeding Pollination management, Breeding