Acultigen (from Latin cultus 'cultivated' and gens 'kind'), orcultivated plant,[note 1] is a plant that has been deliberatelyaltered or selected by humans,[2] by means ofgenetic modification,graft-chimaeras,plant breeding, or wild or cultivated plant selection. These plants have commercial value inhorticulture,agriculture andforestry. Plants meeting this definition remain cultigens whether they arenaturalised, deliberately planted in the wild, or grown in cultivation.
The traditional method of scientific naming is under theInternational Code of Nomenclature for algae, fungi, and plants, and many of the most important cultigens, likemaize (Zea mays) andbanana (Musa acuminata), are named. The items in the list can be in any rank.[3] It is more common currently for cultigens to be given names in accordance with theInternational Code of Nomenclature for Cultivated Plants (ICNCP) principles, rules and recommendations, which provide for the names of cultigens in three categories: thecultivar, theGroup (formerly the cultivar-group), and thegrex.[note 2] The ICNCP does not recognize the use of trade designations and other marketing devices as scientifically acceptable names; it does provide advice on how they should be presented.[4]
Not all cultigens have been given names according to the ICNCP. Apart from ancient cultigens, there may be occasional anthropogenic plants, such as those that are the result of breeding, selection, and tissue grafting, that are considered of no commercial value and have therefore not been given names according to the ICNCP.
The wordcultigen was coined in 1918[5] byLiberty Hyde Bailey (1858–1954), an American horticulturist, botanist and cofounder of theAmerican Society for Horticultural Science. He created the term from the thought of a need for special categories for cultivated plants that had arisen by intentional human activity and which would not fit neatly into theLinnaean hierarchical classification of ranks used by theInternational Rules of Botanical Nomenclature (which later became theInternational Code of Nomenclature for algae, fungi, and plants).
In his 1918 paper, Bailey noted that for anyone preparing a descriptive account of the cultivated plants of a region (he was at that time preparing such an account for North America), it would be clear that there are twogentes or kinds (Latin singulargens, pluralgentes) of plants. Firstly, he referred to those that are of known origin or nativity "of known habitat" asindigens; the other kind was "a domesticated group of which the origin may be unknown or indefinite, which has such characters as to separate it from known indigens, and which is probably not represented by any type specimen or exact description, having, therefore, no clear taxonomic beginning".
He called this second kind of plant a cultigen; the word was thought to be derived from the combination of the Latincultus ('cultivated') andgens ('kind'). In 1923, Bailey emphasised that he was dealing with plants at the rank of species, referring to indigens as those that are discovered in the wild and cultigens as plants that arise in some way under the hand of man.[6] He then defined a cultigen as a species, or its equivalent, that has appeared under domestication. Bailey soon altered his 1923 definition of cultigen when, in 1924, he gave a new definition in the Glossary of hisManual of Cultivated Plants[7] as:
Plant or group known only in cultivation; presumably originating under domestication; contrast with indigen
The 1924 definition of the cultigen permits the recognition of cultivars; the 1923 definition restricts the idea of the cultigen to plants at the rank of species. In later publications of theLiberty Hyde Bailey Hortorium, Cornell, the idea of the cultigen having the rank of species returned (e.g.,Hortus Second in 1941 andHortus Third in 1976).[8][9] Both of these publications indicate that the termscultigen andcultivar are not synonymous and that cultigens exist at the rank of species only.
A cultigen is a plant or group of apparent specific rank, known only in cultivation, with no determined nativity, presumably having originated, in the form in which we know it, under domestication. Compare indigen. Examples areCucurbita maxima,Phaseolus vulgaris,Zea mays.
Botanical historian Alan Morton thought that wild and cultivated plants (cultigens) were of interest to the ancient Greek botanists (partly for religious reasons) and that the distinction was discussed in some detail byTheophrastus, the "Father of Botany". Theophrastus accepted the view that it was human action, not divine intervention, that produced cultivated plants (cultigens) from wild plants, and he also "had an inkling of the limits of culturally induced (phenotypic) changes and of the importance of genetic constitution" (Historia Plantarum III, 2,2 andCausa Plantarum I, 9,3). He also states that cultivated varieties of fruit trees would degenerate if cultivated from seed.[10]
In his 1923 paper, Bailey established a new category for the cultivar. Bailey was never explicit about theetymology of the wordcultivar; it has been suggested that it is a contraction of the wordscultigen orcultivated andvariety.[11] He defined cultivar in his 1923 paper as:
a race subordinate to species, that has originated and persisted under cultivation; it is not necessarily, however, referable to a recognised botanical species. It is essentially the equivalent of the botanical variety except in respect to its origin
In botanical literature, the wordcultigen is generally used to denote a plant that, like thebread wheat (Triticum aestivum), is of unknown origin or presumed to be an ancient human selection. Plants like bread wheat have been givenbinomials according to theBotanical Code and therefore have names with the same form as those of plant species that occur naturally in the wild, but it is not necessary for a cultigen to have a species name or to have the biological characteristics that distinguish aspecies. Cultigens can have names at any of various other ranks, including cultivar names, names in the categories ofgrex andgroup,variety names, andforma names, or they may be plants that have been altered by humans (includinggenetically modified plants) but which have not been given formal names.[12]
In 1918, L.H. Bailey distinguished native plants from those originating in cultivation by designating the former as indigens (indigenous or native to the region) and the latter as cultigens. At the same time, he proposed the termcultivar to distinguish varieties originating in cultivation from botanical varieties known first in the wild.[13] In 1953, the firstInternational Code of Nomenclature for Cultivated Plants was published, in which Bailey's termcultivar was introduced. In the same year, the eponymous journal commemorating the work of Bailey (who died in 1954),Baileya, was published. In the first volume ofBaileya George Lawrence, taxonomist and colleague of Bailey, wrote a short article on the distinction between the new termscultivar andvariety, and to clarify the termtaxon, which had been introduced by German biologist Meyer in the 1920s. He opens the article:
In horticulture, the definitions and uses of the termscultigen andcultivar have varied, and a wider use of the termcultigen has been proposed.[2] The definition given in the Botanical Glossary ofThe New Royal Horticultural Society Dictionary of Gardening defines a cultigen as "a plant found only in cultivation or in the wild having escaped from cultivation; included here are many hybrids and cultivars".[14] TheCultivated Plant Code states that cultigens are "maintained as recognisable entities solely by continued propagation"[4] and thus would not include plants that have evolved after escape from cultivation.
Recent usage in horticulture has maintained a distinction betweencultigen andcultivar while allowing the inclusion of cultivars within the definition ofcultigen.Cultigen is a general-purpose term encompassing plants with cultivar names and others as well, whilecultivar is a formal category in the ICNCP. The definition refers to a "deliberate" (long-term propagation) selection of particular plant characteristics that are not exhibited by a plant's wild counterparts. Occasionally, cultigens escape from cultivation and go into the wild, where they breed with indigenous plants. Selections may be made from the progeny in the wild and brought back into cultivation where they are used for breeding, and the results of the breeding again escape into the wild to breed with indigenous plants; an example of this is the plantLantana.[This paragraph needs citation(s)]
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