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A cultigen (), or cultivated plant, is a plant that has been deliberately altered or selected by humans, by means of genetic modification, , plant breeding, or wild or cultivated plant selection. These plants have commercial value in horticulture, agriculture and forestry. Plants meeting this definition remain cultigens whether they are naturalised, deliberately planted in the wild, or grown in cultivation.
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.
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 two gentes or kinds (Latin singular , plural ) of plants. Firstly, he referred to those that are of known origin or nativity "of known habitat" as ; 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 Latin cultus ('cultivated') and gens ('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.Bailey, L. H. 1923. Various cultigens, and transfers in nomenclature. Gentes Herb. 1:113–136 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 his Manual of Cultivated Plants as:
Plant or group known only in cultivation; presumably originating under domestication; contrast with indigen
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 are Cucurbita 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 by Theophrastus, 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 (phenotype) changes and of the importance of genetic constitution" ( Historia Plantarum III, 2,2 and Causa Plantarum I, 9,3). He also states that cultivated varieties of fruit trees would degenerate if cultivated from seed.
In his 1923 paper, Bailey established a new category for the cultivar. Bailey was never explicit about the etymology of the word cultivar; it has been suggested that it is a contraction of the words cultigen or cultivated and variety.Trehane, P. 2004. 50 years of the International Code of Nomenclature for Cultivated Plants. Acta Horticulturae 634: 17-27. 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 horticulture, the definitions and uses of the terms cultigen and cultivar have varied, and a wider use of the term cultigen has been proposed. The definition given in the Botanical Glossary of The 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". The Cultivated Plant Code states that cultigens are "maintained as recognisable entities solely by continued propagation" and thus would not include plants that have evolved after escape from cultivation.
Recent usage in horticulture has maintained a distinction between cultigen and cultivar while allowing the inclusion of cultivars within the definition of cultigen. Cultigen is a general-purpose term encompassing plants with cultivar names and others as well, while cultivar 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 plant Lantana.
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