In
horticultureHorticulture is the industry and science of plant cultivation. Some would say that horticulture is the process of preparing soil for the planting of seeds, tubers, or cuttings. Horticulturists work and conduct research in the disciplines of plant propagation and cultivation, crop production, plant...
, a
graft-chimaera may arise in
grafting
Grafting is a method of asexual plant propagation widely used in agriculture and horticulture where the tissues of one plant are encouraged to fuse with those of another. It is most commonly used for the propagation of trees and shrubs grown commercially.In most cases, one plant is selected...
at the point of contact between
rootstockA rootstock is a plant, and sometimes just the stump, which already has an established, healthy root system, used for grafting a cutting or budding from another plant. The tree part being grafted onto the rootstock is usually called the scion...
and scion and will have properties intermediate to those of its "parents". A graft-chimaera is not a true hybrid but a mixture of cells, each with the
genotypeThe genotype is the genetic constitution of a cell, an organism, or an individual usually with reference to a specific character under consideration...
of one of its "parents": it is a
chimaeraChimeras in botany are usually single organisms composed of two genetically different types of tissue. They occur in plants, on the same general basis as with animal chimeras...
. Hence, the once widely used term "graft-hybrid" is not descriptive; it is now frowned upon.
Propagation is by cloning only.
Discussion
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In
horticultureHorticulture is the industry and science of plant cultivation. Some would say that horticulture is the process of preparing soil for the planting of seeds, tubers, or cuttings. Horticulturists work and conduct research in the disciplines of plant propagation and cultivation, crop production, plant...
, a
graft-chimaera may arise in
grafting
Grafting is a method of asexual plant propagation widely used in agriculture and horticulture where the tissues of one plant are encouraged to fuse with those of another. It is most commonly used for the propagation of trees and shrubs grown commercially.In most cases, one plant is selected...
at the point of contact between
rootstockA rootstock is a plant, and sometimes just the stump, which already has an established, healthy root system, used for grafting a cutting or budding from another plant. The tree part being grafted onto the rootstock is usually called the scion...
and scion and will have properties intermediate to those of its "parents". A graft-chimaera is not a true hybrid but a mixture of cells, each with the
genotypeThe genotype is the genetic constitution of a cell, an organism, or an individual usually with reference to a specific character under consideration...
of one of its "parents": it is a
chimaeraChimeras in botany are usually single organisms composed of two genetically different types of tissue. They occur in plants, on the same general basis as with animal chimeras...
. Hence, the once widely used term "graft-hybrid" is not descriptive; it is now frowned upon.
Propagation is by cloning only. In practice graft-chimaeras are not noted for their stability and may easily revert back to one of the "parents".
Nomenclature
Article 21 of the
ICNCPThe International Code of Nomenclature for Cultivated Plants regulates the naming of cultivars, cultivar Groups and graft-chimaeras...
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 "+":
- Crataegus + Mespilus
- a name:
- if the "parents" belong to different genera
In biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
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 ICBNThe International Code of Botanical Nomenclature is the set of rules and recommendations dealing with the formal botanical names that are given to plants. Its intent is that each taxonomic group of plants has only one correct name that is accepted worldwide...
. For example +Crataegomespilus+Crataegomespilus is the generic name applied to graft-chimeras between the genera Crataegus and Mespilus. It is not to be confused with ×Crataemespilus, which is applied to sexual hybrids between those genera, nor with Chamaemespilus which is a segregate genus or subgenus of Sorbus....
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 ICBN 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 cultivated plant that has been selected and given a unique name because of desired characteristics; it is usually distinct from similar plants and when propagated it retains those characteristics....
name. For example Syringa 'Correlata' is a graft-chimaera involving Syringa vulgaris (common lilac) and Syringa ×chinensis (Rouen lilac, which is itself a hybrid between S. vulgaris and S. laciniata). No plus sign is used, because both "parents" belong to the genus Syringa.
A graft-chimaera cannot have a
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
name, because it is simultaneously two species. Although
+Laburnocytisus 'Adamii'+Laburnocytisus 'Adamii' is a horticultural curiosity; a small tree which is a graft-chimaera between two species, a laburnum, Laburnum anagyroides, and a broom, Chamaecytisus purpureus +Laburnocytisus 'Adamii' (also known as Adam's laburnum or broom laburnum) is a horticultural curiosity; a...
, for example, is sometimes seen written as if it were a species (+
Laburnocytisus adamii), this is incorrect.
Graft Hybrids in Darwin's works
Charles Darwin
«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.