Binomial nomenclature

From Wikipedia, the free encyclopedia

Binomial nomenclature ("two-term naming system") also called binominal nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages. Such a name is called a binomial name (which may be shortened to just "binomial"), a binomen, binominal name or a scientific name; more informally it is also called a Latin name. The first part of the name identifies the genus to which the species belongs; the second part – the specific name or specific epithet – identifies the species within the genus. For example, humans belong to the genus Homo and within this genus to the species Homo sapiens. Tyrannosaurus rex is probably the most widely known binomial. The formal introduction of this system of naming species is credited to Carl Linnaeus, effectively beginning with his work Species Plantarum in 1753. But Gaspard Bauhin, in as early as 1623, had introduced in his book Pinax theatri botanici (English, Illustrated exposition of plants) many names of genera that were later adopted by Linnaeus.

The application of binomial nomenclature is now governed by various internationally agreed codes of rules, of which the two most important are the International Code of Zoological Nomenclature (ICZN) for animals and the International Code of Nomenclature for algae, fungi, and plants (ICN). Although the general principles underlying binomial nomenclature are common to these two codes, there are some differences, both in the terminology they use and in their precise rules.

In modern usage, the first letter of the first part of the name, the genus, is always capitalized in writing, while that of the second part is not, even when derived from a proper noun such as the name of a person or place. Similarly, both parts are italicized when a binomial name occurs in normal text (or underlined in handwriting). Thus the binomial name of the annual phlox (named after botanist Thomas Drummond) is now written as Phlox drummondii.

In scientific works, the authority for a binomial name is usually given, at least when it is first mentioned, and the date of publication may be specified.

• In zoology
  • "Patella vulgata Linnaeus, 1758". The name "Linnaeus" tells the reader who it was that first published a description and name for this species of limpet; 1758 is the date of the publication in which the original description can be found (in this case the 10th edition of the book Systema Naturae).
  • "Passer domesticus (Linnaeus, 1758)". The original name given by Linnaeus was Fringilla domestica; the parentheses indicate that the species is now considered to belong in a different genus. The ICZN does not require that the name of the person who changed the genus be given, nor the date on which the change was made, although nomenclatorial catalogs usually include such information.
• In botany
  • "Amaranthus retroflexus L." – "L." is the standard abbreviation used in botany for "Linnaeus".
  • "Hyacinthoides italica (L.) Rothm. – Linnaeus first named this bluebell species Scilla italica; Rothmaler transferred it to the genus Hyacinthoides; the ICN does not require that the dates of either publication be specified.

Origin

The name is composed of two word-forming elements: "bi", a Latin prefix for two, and "-nomial", relating to a term or terms. The word "binomium" was used in Medieval Latin to mean a two-term expression in mathematics.

History

Carl Linnaeus (1707–1778), a Swedish botanist, invented the modern system of binomial nomenclature

Prior to the adoption of the modern binomial system of naming species, a scientific name consisted of a generic name combined with a specific name that was from one to several words long. Together they formed a system of polynomial nomenclature. These names had two separate functions. First, to designate or label the species, and second, to be a diagnosis or description; however these two goals were eventually found to be incompatible. In a simple genus, containing only two species, it was easy to tell them apart with a one-word genus and a one-word specific name; but as more species were discovered the names necessarily became longer and unwieldy, for instance Plantago foliis ovato-lanceolatus pubescentibus, spica cylindrica, scapo tereti ("Plantain with pubescent ovate-lanceolate leaves, a cylindric spike and a terete scape"), which we know today as Plantago media.

Such "polynomial names" may sometimes look like binomials, but are significantly different. For example, Gerard's herbal (as amended by Johnson) describes various kinds of spiderwort: "The first is called Phalangium ramosum, Branched Spiderwort; the second, Phalangium non ramosum, Unbranched Spiderwort. The other ... is aptly termed Phalangium Ephemerum Virginianum, Soon-Fading Spiderwort of Virginia". The Latin phrases are short descriptions, rather than identifying labels.

The Bauhins, in particular Caspar Bauhin (1560–1624), took some important steps towards the binomial system, by pruning the Latin descriptions, in many cases to two words. The adoption by biologists of a system of strictly binomial nomenclature is due to Swedish botanist and physician Carl von Linné, more commonly known by his Latinized name Carl Linnaeus (1707–1778). It was in his 1753 Species Plantarum that he first began consistently using a one-word "trivial name" together with a generic name in a system of binomial nomenclature. This trivial name is what is now known as a specific epithet (ICN) or specific name (ICZN). The Bauhins' genus names were retained in many of these, but the descriptive part was reduced to a single word.

Linnaeus's trivial names introduced an important new idea, namely that the function of a name could simply be to give a species a unique label. This meant that the name no longer need be descriptive; for example both parts could be derived from the names of people. Thus Gerard's Phalangium ephemerum virginianum became Tradescantia virginiana, where the genus name honoured John Tradescant the Younger, an English botanist and gardener. A bird in the parrot family was named Psittacus alexandri, meaning "Alexander's parrot", after Alexander the Great whose armies introduced eastern parakeets to Greece. Linnaeus's trivial names were much easier to remember and use than the parallel polynomial names and eventually replaced them.

Value

The value of the binomial nomenclature system derives primarily from its economy, its widespread use, and the uniqueness and stability of names it generally favors:

• Economy. Compared to the polynomial system which it replaced, a binomial name is shorter and easier to remember. It corresponds to the widespread system of family name plus given name(s) used to name people in many cultures.
• Widespread use. The binomial system of nomenclature is governed by international codes and is used by biologists worldwide. A few binomials have also entered common speech, such as Homo sapiens, E. coli, Boa constrictor, and Tyrannosaurus rex.
• Uniqueness. Provided that taxonomists agree as to the limits of a species, it can have only one name that is correct under the appropriate nomenclature code, generally the earliest published if two or more names are accidentally assigned to a species. However, establishing that two names actually refer to the same species and then determining which has priority can be difficult, particularly if the species was named by biologists from different countries. Therefore, a species may have more than one regularly used name; all but one of these names are "synonyms".
• Stability. Although stability is far from absolute, the procedures associated with establishing binomial names, such as the principle of priority, tend to favor stability. For example, when species are transferred between genera (as not uncommonly happens as a result of new knowledge), if possible the second part of the binomial is kept the same. Thus there is disagreement among botanists as to whether the genera Chionodoxa and Scilla are sufficiently different for them to be kept separate. Those who keep them separate give the plant commonly grown in gardens in Europe the name Chionodoxa siehei; those who do not give it the name Scilla siehei. The siehei element is constant. Similarly if what were previously thought to be two distinct species are demoted to a lower rank, such as subspecies, where possible the second part of the binomial name is retained as the third part of the new name. Thus the Tenerife robin may be treated as a different species from the European robin, in which case its name is Erithacus superbus, or as only a subspecies, in which case its name is Erithacus rubecula superbus. The superbus element of the name is constant.

Problems

Binomial nomenclature for species has the effect that when a species is moved from one genus to another, sometimes the specific name or epithet must be changed as well. This may happen because the specific name is already used in the new genus, or to agree in gender with the new genus. Some biologists have argued for the combination of the genus name and specific epithet into a single unambiguous name, or for the use of uninomials (as used in nomenclature of ranks above species).

Because binomials are unique only within a kingdom, it is possible for two or more species to share the same binomial if they occur in different kingdoms. At least five instances of such binomial duplication occur.

Relationship to classification and taxonomy

Nomenclature (including binomial nomenclature) is not the same as classification, although the two are related. Classification is the ordering of items into groups based on similarities or differences; in biological classification, species are one of the kinds of item to be classified. In principle, the names given to species could be completely independent of their classification. This is not the case for binomial names, since the first part of a binomial is the name of the genus into which the species is placed. Above the rank of genus, binomial nomenclature and classification are partly independent; for example, a species retains its binomial name if it is moved from one family to another or from one order to another, unless it better fits a different genus in the same or different family, or it is split from its old genus and placed in a newly created genus. The independence is only partial since the names of families and other higher taxa are usually based on genera.

Taxonomy includes both nomenclature and classification. Its first stages (sometimes called "alpha taxonomy") are concerned with finding, describing and naming species of living or fossil organisms. Binomial nomenclature is thus an important part of taxonomy as it is the system by which species are named. Taxonomists are also concerned with classification, including its principles, procedures and rules.

Derivation of binomial names

A complete binomial name is always treated grammatically as if it were a phrase in the Latin language (hence the common use of the term "Latin name" for a binomial name). However, the two parts of a binomial name can each be derived from a number of sources, of which Latin is only one. These include:

• Latin, either classical or medieval. Thus, both parts of the binomial name Homo sapiens are Latin words, meaning "wise" (sapiens) "human/man" (Homo).
• Classical Greek. The genus Rhododendron was named by Linnaeus from the Greek word ῥοδόδενδρον, itself derived from rhodon, "rose", and dendron, "tree". Greek words are often converted to a Latinized form. Thus coca (the plant from which cocaine is obtained) has the name Erythroxylum coca. Erythroxylum is derived from the Greek words erythros, red, and xylon, wood. The Greek neuter ending -ον (-on) is often converted to the Latin neuter ending -um.
• Other languages. The second part of the name Erythroxylum coca is derived from kuka, the name of the plant in Aymara and Quechua. Since many dinosaur fossils were found in Mongolia, their names often use Mongolian words, e.g. Tarchia from tarkhi, meaning "brain", or Saichania meaning "beautiful one".
• Names of people (often naturalists or biologists). The name Magnolia campbellii commemorates two people: Pierre Magnol, a French botanist, and Archibald Campbell, a doctor in British India.
• Names of places. The lone star tick, Amblyomma americanum, is widespread in the United States.
• Other sources. Some binominal names have been constructed from anagrams or other re-orderings of existing names. Thus the name of the genus Muilla is derived by reversing the name Allium. Names may also be derived from jokes or puns. For example, Ratcliffe described a number of species of rhinoceros beetle, including Cyclocephala nodanotherwon.

The first part of the name, which identifies the genus, must be a word which can be treated as a Latin singular noun in the nominative case. It must be unique within each kingdom, but can be repeated between kingdoms. Thus Huia recurvata is an extinct species of plant, found as fossils in Yunnan, China, whereas Huia masonii is a species of frog found in Java, Indonesia.

The second part of the name, which identifies the species within the genus, is also treated grammatically as a Latin word. It can have one of a number of forms:

• The second part of a binomial may be an adjective. The adjective must agree with the genus name in gender. Latin has three genders, masculine, feminine and neuter, shown by varying endings to nouns and adjectives. The house sparrow has the binomial name Passer domesticus. Here domesticus ("domestic") simply means "associated with the house". The sacred bamboo is Nandina domestica rather than Nandina domesticus, since Nandina is feminine whereas Passer is masculine. The tropical fruit langsat is a product of the plant Lansium parasiticum, since Lansium is neuter. Some common endings for Latin adjectives in the three genders (masculine, feminine, neuter) are -us, -a, -um (as in the previous example of domesticus); -is, -is, -e (e.g. tristis, meaning "sad"); and -or, -or, -us (e.g. minor, meaning "smaller").
• The second part of a binomial may be a noun in the nominative case. An example is the binomial name of the lion, which is Panthera leo. Grammatically the noun is said to be in apposition to the genus name and the two nouns do not have to agree in gender; in this case, Panthera is feminine and leo is masculine.
• The second part of a binomial may be a noun in the genitive (possessive) case. The genitive case is constructed in a number of ways in Latin, depending on the declension of the noun. Common endings for masculine and neuter nouns are -ii or -i in the singular and -orum in the plural, and for feminine nouns -ae in the singular and -arum in the plural. The noun may be part of a person's name, often the surname, as in the Tibetan antelope (Pantholops hodgsonii), the shrub Magnolia hodgsonii, or the olive-backed pipit (Anthus hodgsoni). The meaning is "of the person named", so that Magnolia hodgsonii means "Hodgson's magnolia". The -ii or -i endings show that in each case Hodgson was a man (not the same one); had Hodgson been a woman, hodgsonae would have been used. The person commemorated in the binomial name is not usually (if ever) the person who created the name; for example Anthus hodgsoni was named by Charles Wallace Richmond, in honour of Hodgson. Rather than a person, the noun may be related to a place, as with Latimeria chalumnae, meaning "of the Chalumna River". Another use of genitive nouns is in, for example, the name of the bacterium Escherichia coli, where coli means "of the colon". This formation is common in parasites, as in Xenos vesparum, where vesparum means "of the wasps", since Xenos vesparum is a parasite of wasps.

Whereas the first part of a binomial name must be unique within a kingdom, the second part is quite commonly used in two or more genera (as is shown by examples of hodgsonii above). The full binomial name must be unique within a kingdom.

Codes

From the early 19th century onwards it became ever more apparent that a body of rules was necessary to govern scientific names. In the course of time these became nomenclature codes. The International Code of Zoological Nomenclature (ICZN) governs the naming of animals, the International Code of Nomenclature for algae, fungi, and plants (ICN) that of plants (including cyanobacteria), and the International Code of Nomenclature of Bacteria (ICNB) that of bacteria (including Archaea). Virus names are governed by the International Committee on Taxonomy of Viruses (ICTV), a taxonomic code, which determines taxa as well as names. These codes differ in certain ways, e.g.:

• "Binomial nomenclature" is the correct term for botany, although it is also used by zoologists. Since 1953, "binominal nomenclature" is the technically correct term in zoology. A binominal name is also called a binomen (plural binomina).
• Both codes consider the first part of the two-part name for a species to be the "generic name". In the zoological code (ICZN), the second part of the name is a "specific name". In the botanical code (ICN), it is a "specific epithet". Together, these two parts are referred to as a "species name" or "binomen" in the zoological code; or "species name", "binomial", or "binary combination" in the botanical code. "Species name" is the only term common to the two codes.
• The ICN, the plant code, does not allow the two parts of a binomial name to be the same (such a name is called a tautonym), whereas the ICZN, the animal code, does. Thus the American bison has the binomial Bison bison; a name of this kind would not be allowed for a plant.
• The starting points, the time from which these codes are in effect (retroactively), vary from group to group. In botany the starting point will often be in 1753 (the year Carl Linnaeus first published Species Plantarum). In zoology the starting point is 1758 (1 January 1758 is considered the date of the publication of Linnaeus's Systema Naturae, 10th Edition, and also Clerck's Aranei Svecici). Bacteriology started anew, with a starting point on 1 January 1980.

Summary of terminology for the names of species in the ICZN and ICN

Code	Full name	First part	Second part
ICZN	species name, binomen, binominal name	generic name, genus name	specific name
ICN	species name, binary combination, binomial (name)	generic name	specific epithet

Unifying the different codes into a single code, the "BioCode", has been suggested, although implementation is not in sight. (There is also a code in development for a different system of classification which does not use ranks, but instead names clades. This is called the PhyloCode.)

Differences in handling personal names

As noted above, there are some differences between the codes in the way in which binomials can be formed; for example the ICZN allows both parts to be the same, while the ICN does not. Another difference is in the way in which personal names are used in forming specific names or epithets. The ICN sets out precise rules by which a personal name is to be converted to a specific epithet. In particular, names ending in a consonant (but not "er") are treated as first being converted into Latin by adding "-ius" (for a man) or "-ia" (for a woman), and then being made genitive (i.e. meaning "of that person or persons"). This produces specific epithets like lecardii for Lecard (male), wilsoniae for Wilson (female), and brauniarum for the Braun sisters. By contrast the ICZN does not require the intermediate creation of a Latin form of a personal name, allowing the genitive ending to added directly to the personal name. This explains the difference between the names of the plant Magnolia hodgsonii and the bird Anthus hodgsoni. Furthermore, the ICN requires names not published in the form required by the code to be corrected to conform to it, whereas the ICZN is more protective of the form used by the original author.

Writing binomial names

By tradition, the binomial names of species are usually typeset in italics; for example, Homo sapiens. Generally, the binomial should be printed in a font style different from that used in the normal text; for example, "Several more Homo sapiens fossils were discovered." When handwritten, a binomial name should be underlined; for example, Homo sapiens.

The first part of the binomial, the genus name, is always written with an initial capital letter. In current usage, the second part is never written with an initial capital. Older sources, particularly botanical works published before the 1950s, use a different convention. If the second part of the name is derived from a proper noun, e.g. the name of a person or place, a capital letter was used. Thus the modern form Berberis darwinii was written as Berberis Darwinii. A capital was also used when the name is formed by two nouns in apposition, e.g. Panthera Leo or Centaurea Cyanus.

When used with a common name, the scientific name often follows in parentheses, although this varies with publication. For example, "The house sparrow (Passer domesticus) is decreasing in Europe."

The binomial name should generally be written in full. The exception to this is when several species from the same genus are being listed or discussed in the same paper or report, or the same species is mentioned repeatedly; in which case the genus is written in full when it is first used, but may then be abbreviated to an initial (and a period/full stop). For example, a list of members of the genus Canis might be written as "Canis lupus, C. aureus, C. simensis". In rare cases, this abbreviated form has spread to more general use; for example, the bacterium Escherichia coli is often referred to as just E. coli, and Tyrannosaurus rex is perhaps even better known simply as T. rex, these two both often appearing in this form in popular writing even where the full genus name has not already been given.
The abbreviation "sp." is used when the actual specific name cannot or need not be specified. The abbreviation "spp." (plural) indicates "several species". These abbreviations are not italicised (or underlined). For example: "Canis sp." means "an unspecified species of the genus Canis", while "Canis spp." means "two or more species of the genus Canis". (The abbreviations "sp." and "spp." can easily be confused with the abbreviations "ssp." (zoology) or "subsp." (botany), plurals "sspp." or "subspp.", referring to one or more subspecies. See trinomen (zoology) and infraspecific name.)

The abbreviation "cf." (i.e. confer in Latin) is used to compare individuals/taxa with known/described species. Conventions for use of the "cf." qualifier vary. In paleontology, it is typically used when the identification is not confirmed. For example, "Corvus cf. nasicus" was used to indicate "a fossil bird similar to the Cuban crow but not certainly identified as this species". In molecular systematics papers, "cf." may be used to indicate one or more undescribed species assumed related to a described species. For example, in a paper describing the phylogeny of small benthic freshwater fish called darters, five undescribed putative species (Ozark, Sheltowee, Wildcat, Ihiyo, and Mamequit darters), notable for brightly colored nuptial males with distinctive color patterns, were referred to as "Etheostoma cf. spectabile" because they had been viewed as related to, but distinct from, Etheostoma spectabile (orangethroat darter). This view was supported in varying degrees by DNA analysis. The somewhat informal use of taxa names with qualifying abbreviations is referred to as open nomenclature and it is not subject to strict usage codes.

In some contexts the dagger symbol ("†") may be used before or after the binomial name to indicate that the species is extinct.

Authority

In scholarly texts, at least the first or main use of the binomial name is usually followed by the "authority" – a way of designating the scientist(s) who first published the name. The authority is written in slightly different ways in zoology and botany. For names governed by the ICZN the surname is usually written in full together with the date (normally only the year) of publication. The ICZN recommends that the "original author and date of a name should be cited at least once in each work dealing with the taxon denoted by that name." For names governed by the ICN the name is generally reduced to a standard abbreviation and the date omitted. The International Plant Names Index maintains an approved list of botanical author abbreviations. Historically, abbreviations were used in zoology too.

When the original name is changed, e.g. the species is moved to a different genus, both codes use parentheses around the original authority; the ICN also requires the person who made the change to be given. Some examples:

• (Plant) Amaranthus retroflexus L. – "L." is the standard abbreviation for "Linnaeus"; the absence of parentheses shows that this is his original name.
• (Plant) Hyacinthoides italica (L.) Rothm. – Linnaeus first named the Italian bluebell Scilla italica; Rothmaler transferred it to the genus Hyacinthoides.
• (Animal) Passer domesticus (Linnaeus, 1758) – the original name given by Linnaeus was Fringilla domestica; unlike the ICN, the ICZN does not require the name of the person who changed the genus to be given.

Other ranks

Binomial nomenclature, as described here, is a system for naming species. Implicitly it includes a system for naming genera, since the first part of the name of the species is a genus name. In a classification system based on ranks there are also ways of naming ranks above the level of genus and below the level of species. Ranks above genus (e.g., family, order, class) receive one-part names, which are conventionally not written in italics. Thus the house sparrow, Passer domesticus, belongs to the family Passeridae. Family names are normally based on genus names, although the endings used differ between zoology and botany.

Ranks below species receive three-part names, conventionally written in italics like the names of species. There are significant differences between the ICZN and the ICN. In zoology, the only rank below species is subspecies and the name is written simply as three parts (a trinomen). Thus one of the subspecies of the olive-backed pipit is Anthus hodgsoni berezowskii. In botany, there are many ranks below species and although the name itself is written in three parts, a "connecting term" (not part of the name) is needed to show the rank. Thus the American black elder is Sambucus nigra subsp. canadensis; the white-flowered form of the ivy-leaved cyclamen is Cyclamen hederifolium f. albiflorum.

Cultivar

From Wikipedia, the free encyclopedia

Osteospermum 'Pink Whirls'
A cultivar selected for its intriguing and colourful flowers

The term cultivar most commonly refers to an assemblage of plants selected for desirable characters that are maintained during propagation. More generally, cultivar refers to the most basic classification category of cultivated plants in the International Code of Nomenclature for Cultivated Plants (ICNCP). Most cultivars arose in cultivation, but a few are special selections from the wild.

Popular ornamental garden plants like roses, camellias, daffodils, rhododendrons, and azaleas are cultivars produced by careful breeding and selection for floral colour and form. Similarly, the world's agricultural food crops are almost exclusively cultivars that have been selected for characters such as improved yield, flavour, and resistance to disease, and very few wild plants are now used as food sources. Trees used in forestry are also special selections grown for their enhanced quality and yield of timber.

Cultivars form a major part of Liberty Hyde Bailey's broader group, the cultigen, which is defined as a plant whose origin or selection is primarily due to intentional human activity. A cultivar is not the same as a botanical variety, which is a taxonomic rank below subspecies, and there are differences in the rules for creating and using the names of botanical varieties and cultivars. In recent times, the naming of cultivars has been complicated by the use of statutory patents for plants and recognition of plant breeders' rights.

The International Union for the Protection of New Varieties of Plants (UPOV – French: Union internationale pour la protection des obtentions végétales) offers legal protection of plant cultivars to persons or organisations that introduce new cultivars to commerce. UPOV requires that a cultivar be "distinct, uniform", and "stable". To be "distinct", it must have characters that easily distinguish it from any other known cultivar. To be "uniform" and "stable", the cultivar must retain these characters in repeated propagation.

The naming of cultivars is an important aspect of cultivated plant taxonomy, and the correct naming of a cultivar is prescribed by the Rules and Recommendations of the International Code of Nomenclature for Cultivated Plants (ICNCP, commonly denominated the Cultivated Plant Code). A cultivar is given a cultivar name, which consists of the scientific Latin botanical name followed by a cultivar epithet. The cultivar epithet is usually in a vernacular language. For example, the full cultivar name of the King Edward potato is Solanum tuberosum 'King Edward'. 'King Edward' is the cultivar epithet, which, according to the Rules of the Cultivated Plant Code, is bounded by single quotation marks.

Etymology

Liberty Hyde Bailey (1858–1954) coined the words cultigen in 1918 and cultivar in 1923.

The word cultivar originated from the need to distinguish between wild plants and those with characteristics that arose in cultivation, presently denominated cultigens. This distinction dates to the Greek philosopher Theophrastus (370–285 BC), the "Father of Botany", who was keenly aware of this difference. Botanical historian Alan Morton noted that Theophrastus in his Historia Plantarum (Enquiry into Plants) "had an inkling of the limits of culturally induced (phenotypic) changes and of the importance of genetic constitution" (Historia Plantarum, Book 3, 2, 2 and Causa Plantarum, Book 1, 9, 3).

The International Code of Nomenclature for algae, fungi, and plants uses as its starting point for modern botanical nomenclature the Latin names in Linnaeus' (1707–1778) Species Plantarum (tenth edition) and Genera Plantarum (fifth edition). In Species Plantarum, Linnaeus enumerated all plants known to him, either directly or from his extensive reading. He recognised the rank of varietas (botanical "variety", a rank below that of species and subspecies) and he indicated these varieties with letters of the Greek alphabet, such as α, β, and λ, before the varietal name, rather than using the abbreviation "var." as is the present convention. Most of the varieties that Linnaeus enumerated were of "garden" origin rather than being wild plants.

In time the need to distinguish between wild plants and those with variations that had been cultivated increased. In the nineteenth century many "garden-derived" plants were given horticultural names, sometimes in Latin and sometimes in a vernacular language. From circa the 1900s, cultivated plants in Europe were recognised in the Scandinavian, Germanic, and Slavic literature as stamm or sorte, but these words could not be used internationally because, by international agreement, any new denominations had to be in Latin. In the twentieth century an improved international nomenclature was proposed for cultivated plants.

Liberty Hyde Bailey of Cornell University in New York, United States created the word cultivar in 1923 when he wrote that:

The cultigen is a species, or its equivalent, that has appeared under domestication – the plant is cultigenous. I now propose another name, cultivar, for a botanical variety, or for a race subordinate to species, that has originated under cultivation; it is not necessarily, however, referable to a recognized botanical species. It is essentially the equivalent of the botanical variety except in respect to its origin.

In that essay, Bailey used only the rank of species for the cultigen, but it was obvious to him that many domesticated plants were more like botanical varieties than species, and that realization appears to have motivated the suggestion of the new category of cultivar.

Bailey created the word cultivar, which is generally assumed to be a portmanteau of cultivated and variety. Bailey never explicitly stated the etymology of cultivar, and it has been suggested that it is instead a contraction of cultigen and variety, which seems correct. The neologism cultivar was promoted as "euphonious" and "free from ambiguity". The first Cultivated Plant Code of 1953 subsequently commended its use, and by 1960 it had achieved common international acceptance.

Cultigens

Bread wheat, Triticum aestivum, is considered a cultigen, and is a distinct species from other wheats according to the biological species concept. Many different cultivars have been created within this cultigen. Many other cultigens are not considered to be distinct species, and can be denominated otherwise.

The words cultigen and cultivar may be confused with each other. A cultigen is any plant that is deliberately selected for or altered in cultivation, as opposed to an indigen; the Cultivated Plant Code states that cultigens are "maintained as recognisable entities solely by continued propagation". Cultigens can have names at any of many taxonomic ranks, including those of grex, species, cultivar group, variety, form, and cultivar; and they may be plants that have been altered in cultivation, including by genetic modification, but have not been formally denominated. A cultigen or a component of a cultigen can be accepted as a cultivar if it is recognisable and has stable characters. Therefore, all cultivars are cultigens, because they originate in cultivation, but not all cultigens are cultivars, because some cultigens have not been formally distinguished and denominated as cultivars.

Formal definition

The Cultivated Plant Code notes that the word cultivar is used in two different senses: first, as a "classification category" the cultivar is defined in Article 2 of the International Code of Nomenclature for Cultivated Plants (2009, 8th edition) as follows: The basic category of cultivated plants whose nomenclature is governed by this Code is the cultivar. There are two other classification categories for cultigens, the grex and the group. The Code then defines a cultivar as a "taxonomic unit within the classification category of cultivar". This is the sense of cultivar that is most generally understood and which is used as a general definition.

A cultivar is an assemblage of plants that (a) has been selected for a particular character or combination of characters, (b) is distinct, uniform and stable in those characters, and (c) when propagated by appropriate means, retains those characters.

Different kinds

A cultivar of the orchid genus Oncidium

Which plants are chosen to be named as cultivars is simply a matter of convenience as the category was created to serve the practical needs of horticulture, agriculture, and forestry.

Members of a particular cultivar are not necessarily genetically identical. The Cultivated Plant Code emphasizes that different cultivated plants may be accepted as different cultivars, even if they have the same genome, while cultivated plants with different genomes may be regarded as the same cultivar. The production of cultivars generally entails considerable human involvement although in a few cases it may be as little as simply selecting variation from plants growing in the wild (whether by collecting growing tissue to propagate from or by gathering seed).

Cultivars generally occur as ornamentals and food crops: Malus 'Granny Smith' and Malus 'Red Delicious' are cultivars of apples propagated by cuttings or grafting, Lactuca 'Red Sails' and Lactuca 'Great Lakes' are lettuce cultivars propagated by seeds. Named cultivars of Hosta and Hemerocallis plants are cultivars produced by micropropagation or division.

Clones

Leucospermum 'Scarlet Ribbon'
A cross performed in Tasmania between L. glabrum and L. tottum

Cultivars that are produced asexually are genetically identical and known as clones; this includes plants propagated by division, layering, cuttings, grafts, and budding. The propagating material may be taken from a particular part of the plant, such as a lateral branch, or from a particular phase of the life cycle, such as a juvenile leaf, or from aberrant growth as occurs with witch's broom. Plants whose distinctive characters are derived from the presence of an intracellular organism may also form a cultivar provided the characters are reproduced reliably from generation to generation. Plants of the same chimera (which have mutant tissues close to normal tissue) or graft-chimeras (which have vegetative tissue from different kinds of plants and which originate by grafting) may also constitute a cultivar.

Seed-produced

Some cultivars "come true from seed", retaining their distinguishing characteristics when grown from seed. Such plants are termed a "variety", "selection" or "strain" but these are ambiguous and confusing words that are best avoided. In general, asexually propagated cultivars grown from seeds produce highly variable seedling plants, and should not be labelled with, or sold under, the parent cultivar's name.

Seed-raised cultivars may be produced by uncontrolled pollination when characteristics that are distinct, uniform and stable are passed from parents to progeny. Some are produced as "lines" that are produced by repeated self-fertilization or inbreeding or "multilines" that are made up of several closely related lines. Sometimes they are F1 hybrids which are the result of a deliberate repeatable single cross between two pure lines. A few F2 hybrid seed cultivars also exist, such as Achillea 'Summer Berries'.

Some cultivars are agamospermous plants, which retain their genetic composition and characteristics under reproduction. Occasionally cultivars are raised from seed of a specially selected provenance – for example the seed may be taken from plants that are resistant to a particular disease.

Genetically modified

Genetically modified plants with characteristics resulting from the deliberate implantation of genetic material from a different germplasm may form a cultivar. However, the International Code of Nomenclature for Cultivated Plants notes, "In practice such an assemblage is often marketed from one or more lines or multilines that have been genetically modified. These lines or multilines often remain in a constant state of development which makes the naming of such an assemblage as a cultivar a futile exercise."  However, retired transgenic varieties such as the Fish tomato, which are no longer being developed, do not run into this obstacle and can be given a cultivar name.

Cultivars may be selected because of a change in the ploidy level of a plant which may produce more desirable characteristics.

Cultivar names

Viola 'Clear Crystals Apricot'
The specific epithet may be omitted from a cultivar name

Every unique cultivar has a unique name within its denomination class (which is almost always the genus). Names of cultivars are regulated by the International Code of Nomenclature for Cultivated Plants, and may be registered with an International Cultivar Registration Authority (ICRA). There are sometimes separate registration authorities for different plant types such as roses and camellias. In addition, cultivars may be associated with commercial marketing names referred to in the Cultivated Plant Code as "trade designations" (see below).

Presenting in text

A cultivar name consists of a botanical name (of a genus, species, infraspecific taxon, interspecific hybrid or intergeneric hybrid) followed by a cultivar epithet. The cultivar epithet is enclosed by single quotes; it should not be italicized if the botanical name is italicized; and each of the words within the epithet is capitalized (with some permitted exceptions such as conjunctions). It is permissible to place a cultivar epithet after a common name provided the common name is botanically unambiguous. Cultivar epithets published before 1 January 1959 were often given a Latin form and can be readily confused with the specific epithets in botanical names; after that date, newly coined cultivar epithets must be in a modern vernacular language to distinguish them from botanical epithets.

Examples of correct text presentation:

Cryptomeria japonica 'Elegans'

Chamaecyparis lawsoniana 'Aureomarginata' (pre-1959 name, Latin in form)

Chamaecyparis lawsoniana 'Golden Wonder' (post-1959 name, English language)

Pinus densiflora 'Akebono' (post-1959 name, Japanese language)

Apple 'Sundown'

Some incorrect text presentation examples:

Cryptomeria japonica "Elegans" (double quotes are unacceptable)

Berberis thunbergii cv. 'Crimson Pygmy' (this once-common usage is now unacceptable, as it is no longer correct to use "cv." in this context; Berberis thunbergii 'Crimson Pygmy' is correct)

Rosa cv. 'Peace' (this is now incorrect for two reasons: firstly, the use of "cv."; secondly, "Peace" is a trade designation or "selling name" for the cultivar R. 'Madame A. Meilland' and should therefore be printed in a different typeface from the rest of the name, without quote marks, for example: Rosa Peace.)

Group names

Where several very similar cultivars exist they can be associated into a Group (formerly Cultivar-group). As Group names are used with cultivar names it is necessary to understand their way of presentation. Group names are presented in normal type and the first letter of each word capitalised as for cultivars, but they are not placed in single quotes. When used in a name, the first letter of the word "Group" is itself capitalized.

Presenting in text

Brassica oleracea Capitata Group (the group of cultivars including all typical cabbages)

Brassica oleracea Botrytis Group (the group of cultivars including all typical cauliflowers)

Hydrangea macrophylla Groupe Hortensia (in French) = Hydrangea macrophylla Hortensia Group (in English)

Where cited with a cultivar name the group should be enclosed in parentheses, as follows:

Hydrangea macrophylla (Hortensia Group) 'Ayesha' 

Legal protection of cultivars and their names

Since the 1990s there has been an increasing use of legal protection for newly produced cultivars. Plant breeders expect legal protection for the cultivars they produce. According to proponents of such protections, if other growers can immediately propagate and sell these cultivars as soon as they come on the market, the breeder's benefit is largely lost. Legal protection for cultivars is obtained through the use of Plant breeders’ rights and plant Patents but the specific legislation and procedures needed to take advantage of this protection vary from country to country.

Controversial use of legal protection for cultivars

The use of legal protection for cultivars can be controversial, particularly for food crops that are staples in developing countries, or for plants selected from the wild and propagated for sale without any additional breeding work; some people consider this practice unethical.

Trade designations and selling names

The formal scientific name of a cultivar, like Solanum tuberosum ‘King Edward’, is a way of uniquely designating a particular kind of plant. This scientific name is in the public domain and cannot be legally protected. Plant retailers wish to maximize their share of the market and one way of doing this is to replace the cumbersome Latin scientific names on plant labels in retail outlets with appealing marketing names that are easy to use, pronounce, and remember. Marketing names lie outside the scope of the Cultivated Plant Code which refers to them as "trade designations". If a retailer or wholesaler has the sole legal rights to a marketing name then that may offer a sales advantage. Plants protected by plant breeders' rights (PBR) may have a "true" cultivar name – the recognized scientific name in the public domain – and a "commercial synonym" – an additional marketing name that is legally protected. An example would be Rosa Fascination = 'Poulmax', in which Rosa is the genus, Fascination is the trade designation, and ‘Poulmax’ is scientific cultivar name.

Because a name that is attractive in one language may have less appeal in another country, a plant may be given different selling names from country to country. Quoting the original cultivar name allows the correct identification of cultivars around the world.

The main body coordinating plant breeders' rights is the International Union for the Protection of New Varieties of Plants (Union internationale pour la protection des obtentions végétales, UPOV) and this organization maintains a database of new cultivars protected by PBR in all countries.

International Cultivar Registration Authorities

Dahlia 'Akita'
A cultivar selected for flower form and colour

An International Cultivar Registration Authority (ICRA) is a voluntary, non-statutory organization appointed by the Commission for Nomenclature and Cultivar Registration of the International Society of Horticultural Science. ICRAs are generally formed by societies and institutions specializing in particular plant genera such as Dahlia or Rhododendron and are currently located in Europe, North America, China, India, Singapore, Australia, New Zealand, South Africa and Puerto Rico.

Each ICRA produces an annual report and its reappointment is considered every four years. The main task is to maintain a register of the names within the group of interest and where possible this is published and placed in the public domain. One major aim is to prevent the duplication of cultivar and Group epithets within a genus, as well as ensuring that names are in accord with the latest edition of the Cultivated Plant Code. In this way, over the last 50 years or so, ICRAs have contributed to the stability of cultivated plant nomenclature. In recent times many ICRAs have also recorded trade designations and trademarks used in labelling plant material, to avoid confusion with established names.

New names and other relevant data are collected by and submitted to the ICRA and in most cases there is no cost. The ICRA then checks each new epithet to ensure that it has not been used before and that it conforms with the Cultivated Plant Code. Each ICRA also ensures that new names are formally established (i.e. published in hard copy, with a description in a dated publication). They record details about the plant, such as parentage, the names of those concerned with its development and introduction, and a basic description highlighting its distinctive characters. ICRAs are not responsible for assessing the distinctiveness of the plant in question. Most ICRAs can be contacted electronically and many maintain web sites: for an up-to-date listing.

Mutation breeding

From Wikipedia, the free encyclopedia

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 sometimes called mutagenic plants or mutagenic seeds. From 1930 to 2014 more than 3200 mutagenic plant varieties were released that have been derived either as direct mutants (70%) or from their progeny (30%). Crop plants account for 75% of released mutagenic species with the remaining 25% ornamentals or decorative plants. However, although the FAO/IAEA reported in 2014 that over 1,000 mutant varieties of major staple crops were being grown worldwide, it is unclear how many of these varieties are currently used in agriculture or horticulture around the world, as these seeds are not always identified or labeled as being mutagen or having a mutagenic provenance.

Process

There are different kinds of mutagenic breeding such as using chemical mutagens like ethyl methanesulfonate and dimethyl sulfate, radiation and transposons are used to generate mutants. Mutation breeding is commonly used to produce traits in crops such as larger seeds, new colors, or sweeter fruits, that either cannot be found in nature or have been lost during evolution.

Radiation breeding

Exposing plants to radiation is sometimes called radiation breeding and is a sub class of mutagenic breeding. Radiation breeding was discovered in the 1920s when Lewis Stadler of the University of Missouri used X-rays on maize and barley. In the case of barley, the resulting plants were white, yellow, pale yellow and some had white stripes. In 1928, Stadler first published his findings on radiation-induced mutagenesis in plants. During the period 1930–2004, radiation-induced mutant varieties were developed primarily using gamma rays (64%) and X-rays (22%).


Radiation breeding may take place in atomic gardens; and seeds have been sent into orbit in order to expose them to more cosmic radiation.

Use of chemical mutagens

High rates of chromosome aberrations resulting from ionizing radiation and the accompanied detrimental effects made researchers look for alternate sources for inducing mutations. As a result, an array of chemical mutagens has been discovered. The most widely used chemical mutagens are alkylating agents. Ethyl methanesulfonate (EMS) is the most popular because of its effectiveness and ease of handling, especially its detoxification through hydrolysis for disposal. Nitroso compounds are the other alkylating agents widely used, but they are light-sensitive and more precautions need to be taken because of their higher volatility. EMS has become a commonly used mutagen for developing large numbers of mutants for screening such as in developing TILLING populations. Although many chemicals are mutagens, only few have been used in practical breeding as the doses need to be optimised and also because the effectiveness is not high in plants for many.

History

According to garden historian Paige Johnson

After WWII, there was a concerted effort to find 'peaceful' uses for atomic energy. One of the ideas was to bombard plants with radiation and produce lots of mutations, some of which, it was hoped, would lead to plants that bore more heavily or were disease or cold-resistant or just had unusual colors. The experiments were mostly conducted in giant gamma gardens on the grounds of national laboratories in the US but also in Europe and countries of the former USSR.

Comparison to other agronomic techniques

In the debate over genetically modified foods, the use of transgenic processes is often compared and contrasted with mutagenic processes. While the abundance and variation of transgenic organisms in human food systems, and their effect on agricultural biodiversity, ecosystem health and human health is somewhat well documented, mutagenic plants and their role on human food systems is less well known, with one journalist writing "Though poorly known, radiation breeding has produced thousands of useful mutants and a sizable fraction of the world's crops...including varieties of rice, wheat, barley, pears, peas, cotton, peppermint, sunflowers, peanuts, grapefruit, sesame, bananas, cassava and sorghum." In Canada crops generated by mutation breeding face the same regulations and testing as crops obtained by genetic engineering. Mutagenic varieties tend to be made freely available for plant breeding, in contrast to many commercial plant varieties or germplasm that increasingly have restrictions on their use such as terms of use, patents and proposed genetic user restriction technologies and other intellectual property regimes and modes of enforcement.

Unlike genetically modified crops, which typically involve the insertion of one or two target genes, plants developed via mutagenic processes with random, multiple and unspecific genetic changes have been discussed as a concern but are not prohibited by any nation's organic standards. Reports from the US National Academy of Sciences state that there is no scientific justification for regulating genetic engineered crops while not doing so for mutation breeding crops.

Several organic food and seed companies promote and sell certified organic products that were developed using both chemical and nuclear mutagenesis. Several certified organic brands, whose companies support strict labeling or outright bans on GMO-crops, market their use of branded wheat and other varietal strains which were derived from mutagenic processes without any reference to this genetic manipulation. These organic products range from mutagenic barley and wheat ingredient used in organic beers to mutagenic varieties of grapefruits sold directly to consumers as organic.

New mutagen techniques

Restriction endonucleases

Interest in the use of bacterial restriction endonucleases (RE) to study double-stranded breaks in plant DNA began in the mid-nineties. These breaks in DNA, otherwise known as DSBs, were found to be the source of much chromosomal damage in eukaryotes, causing mutations in plant varieties. REs induce a result on plant DNA similar to that of ionizing radiation or radiomimetic chemicals. Blunt ended breaks in the DNA, unlike sticky ended breaks, were found to produce more variations in chromosomal damage, making them the more useful type of break for mutation breeding. While the connection of REs to chromosomal aberrations is mostly limited to research on mammalian DNA, success in mammalian studies caused scientists to conduct more studies of RE-induced chromosomal and DNA damaged on barley genomes. Due to restriction endonucleases' ability to facilitate damage in chromosomes and DNA, REs have the capability of being used as a new method of mutagenesis to promote the proliferation of mutated plant varieties.

Space-breeding

The ability of plants to develop and thrive is dependent on conditions such as microgravity and cosmic radiation in space. China has been experimenting with this theory by sending seeds into space, testing to see if space flights will cause genetic mutations. Since 1987, China has cultivated 66 mutant varieties from space through their space-breeding program. Chromosomal aberrations greatly increased when seeds were sent into aerospace compared to their earth-bound counterparts. The effect of space flight on seeds depends on their species and variety. For example, space-bred wheat saw a large growth in seed germination in compared to its Earth-bound control, but space-bred rice had no visible advantage compared to its control. For the varieties that were positively mutated by space flight, their growth potential exceeded that of not only their Earth-grown counterparts, but also their irradiated counterparts on Earth. Compared to traditional mutagenic techniques, space-bred mutations have greater efficacy in that they experience positive effects on their first generation of mutation, whereas irradiated crops often see no advantageous mutations in their first generations. Though multiple experiments have shown the positive effects of space flight on seed mutation, there is no clear connection as to what aspect of aerospace has produced such advantageous mutations. There is much speculation around cosmic radiation being the source of chromosomal aberrations, but so far, there has been no concrete evidence of such connection. Though China's space-breeding program has been shown to be very successful, the program requires a large budget and technological support that many other countries are either unwilling or unable to provide, meaning this program is unfeasible outside of China. Due to such restraints, scientists have been trying to replicate space condition on Earth in order to promote the same expedient space-born mutations on Earth. One such replication is a magnetic field-free space (MF), which produces an area with a weaker magnetic field than that of Earth. MF treatment produced mutagenic results, and has been used to cultivate new mutant varieties of rice and alfalfa. Other replications of space conditions include irradiation of seeds by a heavy 7 Li-ion beam or mixed high-energy particles. These space-bred varieties are already being introduced to the public. In 2011, during the National Lotus Flowers Exhibition in China, a mutant lotus, called the "Outer Space Sun", was shown at the flower show.

Ion beam technology

Ion beams mutate DNA by deleting multiple bases from its code. Compared to traditional sources of radiation, like gamma rays and X-rays, ion beams have been shown to cause more severe breaks in DNA that are more difficult to weave back together, causing the change in DNA to be more drastic than changes caused by traditional irradiation. Ion beams change DNA in a manner that makes it look vastly different than its original makeup, more so than when traditional irradiation techniques are used. Most experimentation, using ion beam technology, has been conducted in Japan. Notable facilities using this technology are TIARA of the Japan Atomic Energy Agency, RIKEN Accelerator Research Facility, and various other Japanese institutions. During the process of ion beam radiation, seeds are wedged between two kapton films and irradiated for roughly two minutes. Mutation frequencies are notably higher for ion beam radiation compared to electron radiation, and the mutation spectrum is broader for ion beam radiation compared to gamma ray radiation. The broader mutation spectrum was revealed through the largely varied amount of flower phenotypes produced by ion beams. Flowers mutated by the ion beams exhibited a variety of colors, patterns, and shapes. Through ion beam radiation, new varieties of plants have been cultivated. These plants had the characteristics of being ultraviolet light-B resistant, disease resistant, and chlorophyll-deficient. Ion beam technology has been used in the discovery of new genes responsible for the creation of more robust plants, but its most prevalent use is commercially for producing new flower phenotypes, like striped chrysanthemums.

Mature pollen treated with gamma radiation

Gamma radiation is used on mature rice pollen to produce parent plants used for crossing. The mutated traits in the parent plants are able to be inherited by their offspring plants. Because rice pollen has a very short lifespan, researchers had to blast gamma rays at cultured spikes from rice plants. Through experimentation, it was revealed that there was a greater variety of mutation in irradiated pollen rather than irradiated dry seeds. Pollen treated with 46Gy of gamma radiation showed an increase in grain size overall and other useful variations. Typically, the length of each grain was longer after the crossing of irradiated parent rice plants. The rice progeny also exhibited a less chalky visage, improving on the appearance of the parent rice plants. This technique was used to develop two new rice cultivars, Jiaohezaozhan and Jiafuzhan, in China. Along with facilitating the creation of these two rice cultivars, the irradiation of mature rice pollen has produced roughly two hundred mutant rice lines. Each of these lines produce rice grains of both a higher quality and larger size. The mutations produced by this technique vary with each generation, meaning further breeding of these mutated plants could produce new mutations. Traditionally, gamma radiation is used on solely adult plants, and not on pollen. The irradiation of mature pollen allows mutant plants to grow without being in direct contact with gamma radiation. This discovery is in contrast to what was previously believed about gamma radiation: that it could only elicit mutations in plants and not pollen.

Notable mutagen varieties

 Argentina

• Colorado Irradiado groundnut (mutant created with X-rays; high fat content and yield, 80% of groundnuts grown in Argentina in the 1980s was Colorado Irradiado)
• Puita INTA-CL rice mutant (herbicide resistance and good yield; also grown in Bolivia, Brazil, Costa Rica and Paraguay)

 Australia

• Amaroo rice mutant variety (60-70% of rice grown in Australia was Amaroo in 2001)

 Bangladesh

• Binasail, Iratom-24 and Binadhan-6 rice mutants 
• Binamoog-5 mung bean mutant variety

 Cuba

• Maybel tomato mutant (excellent drought resistance)
• GINES rice mutant (created using proton radiation; grows well in salty conditions)

 People's Republic of China

• Henong series soybean mutants
• Jiahezazhan and Jiafuzhan rice (mutations obtained by pollen irradiation; high yield and quality, very adaptable, resistant to plant hopper and blast)
• Lumian Number 1 cotton
• Purple Orchard 3 Sweet potato
• Tiefeng 18 soybean
• Yangdao Number 6 rice
• Yangmai 156 wheat
• Zhefu 802 rice mutant (irradiated with gamma rays; resistant to rice blast, good yield even in poor conditions, the most planted rice variety between 1986-1994)
• 26Zhaizao indica rice mutant (created with gamma rays)

 Czech Republic

• Diamant barley (high yield, short height mutant created with X-Rays)

 Egypt

• Giza 176 and Sakha 101 high yield rice mutants

 Finland

• Balder J barley mutant (better drought resistance, yield and sprouting)
• Puhti and Ryhti stiff straw oat mutants

 France

• High oleic sunflowers (covering more than 50 % of the sunflower acreage)

 Germany

• Trumpf barley

 Ghana

• Tek bankye mutant cassava (good poundability and increased dry matter content)

 India

• Co-4, Pant Mung-2, and TAP mung bean mutants
• MA-9 cotton - the world's first mutant cotton, released in 1948 (X-ray radiation; drought tolerance, high yielding)
• PNR-381 Rice
• Pusa 408 (Ajay), Pusa 413 (Atul), Pusa 417 (Girnar), and Pusa 547 chickpea mutants (resistant to Ascochyta blight and wilt diseases, and have high yields)
• Sharbati Sonora wheat
• Tau-1, MUM 2, BM 4, LGG 407, LGG 450, Co4, Dhauli (TT9E) and Pant moong-1 blackgram (YMC, (Yellow mosaic virus) resistance)
• TG24 and TG37 groundnut mutants

 Italy

• Durum wheat (especially Creso mutant, created with thermal neutrons)

 Japan

• Osa Gold Pear (disease resistance) 
• Most rice varieties grown in Japan have the sd1 mutant allele from the Reimei rice variety

 Myanmar

• Shwewartun rice mutant (created by irradiating IR5 rice to give better yield, grain quality and earlier maturity)

 Pakistan

• Basmati 370 short height rice mutant
• NIAB-78 cotton mutant (high yielding, heat tolerant, early maturing)
• CM-72 chickpea mutant (created with 150Gy of gamma rays; high yielding, blight resistant)
• NM-28 mungbean mutant (short height, uniform and early maturing, high seed yield)
• NIAB Masoor 2006 lentil mutant (created with 200Gy of radiation; early maturing, high yield, resistant to disease)

 Peru

• UNA La Molina 95 barley mutant (developed in 1995 for growing above 3,000 m)
• Centenario Amarinth "kiwicha" mutant (high quality grain and exported as a certified organic product)
• Centenario II barley mutant (developed for growing in the Andean highlands with high yield, high quality flour and tolerance to hail)

 Sudan

• Albeely banana mutant (better quality, high yield and better stand)

 Thailand

• RD15 and RD6 aromatic indica rice mutants (created with gamma rays and released in 1977-8; RD 15 is early ripening, RD6 has a valuable glutinous endosperm) Thailand is the biggest exporter of aromatic rice in the world

 United Kingdom

• Golden Promise barley (semi-dwarf, salt tolerant mutant created with gamma rays) Is used to make beer and whisky

 United States

• Calrose 76 Rice (short height rice induced with gamma rays)
• Luther and Pennrad barley (high yield mutant varieties; Pennrad also resistant to winter)
• Murray Mitcham Peppermint (Verticillium wilt tolerance)
• Sanilac bean (X-ray radiation; high yielding mutant - also the Gratiot and Sea-way bean varieties were cross-bred from Sanilac)
• Stadler wheat (high yield mutant with resistance to loose smut and leaf rust and earlier maturity)
• Star Ruby and Rio red varieties of the Rio Star Grapefruit (created using thermal neutron techniques)
• Todd's Mitcham Peppermint (Verticillium wilt tolerance)

 Vietnam

• VND 95-20, VND-99-1 and VN121 rice mutants (increased yield, improved quality, resistance to disease and pests)
• DT84, DT96, DT99 and DT 2008 soybean mutants (developed using gamma rays to grow three crops a year, tolerance to heat and cold and resistance to disease)

In 2014, it was reported that 17 rice mutant varieties, 10 soybean, two maize and one chrysanthemum mutant varieties had been officially released to Vietnamese farmers. 15% of rice and 50% of soybean was produced from mutant varieties.

Release by nation

As of 2011 the percentage of all mutagenic varieties released globally, by country, were:

• (25.2%)  People's Republic of China
• (15.0%)  Japan
• (11.5%)  India
• (6.7%)  Russia
• (5.5%)  Netherlands
• (5.3%)  Germany
• (4.3%)  United States
• (2.4%)  Bulgaria
• (1.7%)  Vietnam
• (1.4%)  Bangladesh