horticulture Horticulture is the branch of agriculture that deals with the art, science, technology, and business of plant cultivation. It includes the cultivation of fruits, vegetables, nuts, seeds, herbs, sprouts, mushrooms, algae, flowers, seaweeds and no ...

, a graft-chimaera may arise in

grafting Grafting or graftage is a horticultural technique whereby tissues of plants are joined so as to continue their growth together. The upper part of the combined plant is called the scion () while the lower part is called the rootstock. The succ ...

at the point of contact between

rootstock A rootstock is part of a plant, often an underground part, from which new above-ground growth can be produced. It could also be described as a stem with a well developed root system, to which a bud from another plant is grafted. It can refer to a ...

and

scion Scion may refer to: Arts, entertainment, and media Fictional entities *Scion, a playable class in the game ''Path of Exile'' (2013) *Atlantean Scion, a device in the ''Tomb Raider'' video game series *Scions, an alien race in the video game ''Ba ...

and will have properties intermediate between those of its "parents". A graft-chimaera is not a true

hybrid Hybrid may refer to: Science * Hybrid (biology), an offspring resulting from cross-breeding ** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species ** Hybridity, the property of a hybrid plant which is a union of two dif ...

but a mixture of cells, each with the

genotype The genotype of an organism is its complete set of genetic material. Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a ...

of one of its "parents": it is a

chimaera Chimaeras are cartilaginous fish in the order Chimaeriformes , known informally as ghost sharks, rat fish, spookfish, or rabbit fish; the last three names are not to be confused with rattails, Opisthoproctidae, or Siganidae, respectively. At ...

. Hence, the once widely used term "graft-hybrid" is not descriptive; it is now frowned upon. Propagation is by

cloning Cloning is the process of producing individual organisms with identical or virtually identical DNA, either by natural or artificial means. In nature, some organisms produce clones through asexual reproduction. In the field of biotechnology, cl ...

only. In practice graft-chimaeras are not noted for their stability and may easily revert to one of the "parents".

Nomenclature

Article 21 of the ''

ICNCP The ''International Code of Nomenclature for Cultivated Plants'' (ICNCP), is a guide to the rules and regulations for naming cultigens, plants whose origin or selection is primarily due to intentional human activity. It is also known as Cultivate ...

'' stipulates that a graft-chimaera can be indicated either by * a formula: the names of both "parents", in alphabetical order, joined by the

plus sign The plus and minus signs, and , are mathematical symbols used to represent the notions of positive and negative, respectively. In addition, represents the operation of addition, which results in a sum, while represents subtraction, result ...

"+": : ''Crataegus'' + ''Mespilus'' * a name: ** if the "parents" belong to different

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

a name may be formed by joining part of one generic name to the whole of the other generic name. This name must not be identical to a generic name published under the ''

International Code of Nomenclature for algae, fungi, and plants The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all those "trad ...

'' (''ICN''). For example + ''Crataegomespilus'' is the name for the graft-chimaera which may also be indicated by the formula ''Crataegus'' + ''Mespilus''. This name is clearly different from ×''Crataemespilus'', the name under the ''ICN'' for the true hybrid between ''Crataegus'' and ''Mespilus'', which can also be designated by the formula ''Crataegus'' × ''Mespilus''. ** if both "parents" belong to the same genus the graft-chimaera may be given a

cultivar A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture, ...

name. For example ''Syringa'' 'Correlata' is a graft-chimaera involving ''Syringa vulgaris'' (common lilac) and ''

Syringa × chinensis ''Syringa'' × ''chinensis'', the Chinese lilac or Rouen lilac, is a hybrid species of flowering plant in the family Oleaceae. It was supposedly first noticed growing in Rouen, France in 1777. In spite of its specific and common names, it most p ...

'' (Rouen lilac, which is itself a hybrid between ''S. vulgaris'' and ''S. persica''). No plus sign is used, because both "parents" belong to the genus ''Syringa''. A graft-chimaera cannot have a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

name, because it is simultaneously two species. Although +''Laburnocytisus'' 'Adamii', for example, is sometimes seen written as if it were a species (+''Laburnocytisus adamii''), this is incorrect.

In Darwin's works

Charles Darwi
"The Variation of Animals and Plants Under Domestication"
, 1868 г.:

I will therefore give all the facts which I have been able to collect on the formation of hybrids between distinct species or varieties, without the intervention of the sexual organs. For if, as I am now convinced, this is possible, it is a most important fact, which will sooner or later change the views held by physiologists with respect to sexual reproduction. A sufficient body of facts will afterwards be adduced, showing that the segregation or separation of the characters of the two parent-forms by bud-variation, as in the case of Cytisus adami, is not an unusual though a striking phenomenon. We shall further see that a whole bud may thus revert, or only half, or some smaller segment.

References

{{Reflist Botanical nomenclature

Nomenclature

In Darwin's works

See also

References