Cultigen

A cultigen (from Latin cultus 'cultivated' and gens 'kind'), or cultivated plant, is a plant that has been deliberately altered or selected by humans, by means of genetic modification, graft-chimaeras, 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.

The traditional method of scientific naming is under the International Code of Nomenclature for algae, fungi, and plants, and many of the most important cultigens, like maize (Zea mays) and banana (Musa acuminata), are named. The items in the list can be in any rank. It is more common currently for cultigens to be given names in accordance with the International Code of Nomenclature for Cultivated Plants (ICNCP) principles, rules and recommendations, which provide for the names of cultigens in three categories: the cultivar, the Group (formerly the cultivar-group), and the grex. 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.

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 word cultigen was coined in 1918 by Liberty Hyde Bailey (1858–1954), an American horticulturist, botanist and cofounder of the American 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 the Linnaean hierarchical classification of ranks used by the International Rules of Botanical Nomenclature (which later became the International 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 two gentes or kinds (Latin singular gens, plural gentes) of plants. Firstly, he referred to those that are of known origin or nativity "of known habitat" as indigens; 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. 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

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 the Liberty Hyde Bailey Hortorium, Cornell, the idea of the cultigen having the rank of species returned (e.g., Hortus Second in 1941 and Hortus Third in 1976). Both of these publications indicate that the terms cultigen and cultivar are not synonymous and that cultigens exist at the rank of species only.