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Clone

clone (I)
clone (GB)
clone (F)
clon (ES)
kloon (N)
clone (PO)

Offspring produced from an organism by asexual reproduction (Greek: branch or rice). In humans, identical twins form a natural clone (but with different fingerprints). In plants, this is called vegetative reproduction, when new plants are regenerated from certain tissue parts of an initial plant. In the process, genetically completely identical living beings with hereditary characteristics are initially created, which are 100% identical copies (duplicates) of the original type. Due to spontaneously occurring mutations that accumulate during the life phase, these copies slowly but steadily deviate from the original vine in small steps. However, one can only speak of mutants from a certain larger morphological and genetic scope of change.

Somatic chimeras

In somatic chimeras, the mutations occur in a tissue-specific manner. The outer epidermal cells or the inner cell layers may show one or more mutations. Such chimeras may even be the rule in grapevine, because with the first divisions of the embryo, the basic division of the tissue layers into epidermis and inner cell layers is deterministically established forever. This division of the basic tissues into two is already also contained in each newly formed axillary bud, so that chimerisms are also multiplied during vegetative propagation via cuttings. In sexual reproduction, on the other hand, two parent varieties are crossed so that from each fertilised seed a new grapevine variety grows out, half of which has the newly combined hereditary traits of both parents. Thus, new grapevine varieties are created through targeted cross-breeding by sexual means. However, somatic mutations and vegetative propagation give rise to clone variants, mutants and chimeras.

Clone, mutant and clonal mutant

The three terms clone, mutant and clonal mutant are often used colloquially in viticulture to define the origin of a vine, but this is not correct, because a clone in the strict scientific sense is an identical copy of the original, while a clone in the viticultural sense is a mutated clonal variant and is no longer 100% identical to the original plant. In practice, clones of grapevine varieties are only addressed as clones when they can be at least slightly distinguished from the original type in some visible or measurable individual characteristics, i.e. they are already mutated. Such mutations occur spontaneously and often as bud mutations. Later, after budding, they are multiplied by vegetative propagation of the mutant shoots.

A clonal mutant is a clone (duplicate) of a variety that deviates in some characteristics. Clone mutants are produced by spontaneous mutation of a fruit shoot that has been selected for its deviating characteristics and further propagated vegetatively. However, it is a somewhat imprecise term, the boundaries between clone (which strictly speaking means a hundred percent duplicate), clonal mutant and mutant are fluid. Simply put, clonal mutants can be characterised more by shifts in quantitative traits (higher must weight, lower yield, stronger growth) than by clear visual demarcations based on qualitative traits (berry colour/shape, leaf hairiness, earliness). The Pinot varieties Blauer Arbst, Frühburgunder, Pinot Liébault, Pinot Mariafeld, Pinot Tete de Negre, Pinot Teinturier and Samtrot are often referred to variously as clone, clonal mutant, mutant, biotype or variety.

Grape variety clones/mutations

These mutants can mutate again and develop into independent mutation lines. Thus, especially in the case of old, widespread varieties that have been multiplied millions of times, such as Chasselas, Pinot or Traminer, several regional lineage branches with independent grape variety clones have developed. Very conspicuous grape variety clones are, for example, plants whose berry colour has mutated from blue to violet, grey or red or to yellow and green. Grape varieties such as Chasselas Blanc, Chasselas Rose and Chasselas Rouge, as well as Pinot Gris and Pinot Blanc and many others are such berry colour mutants. The anthocyanins (red pigments) that determine berry colour are produced biochemically in the cells in a chain of synthesis steps. One or more mutations interrupt this chain in the underlying genes so that fewer colour pigments or only the colourless precursors are formed. As a result, either the colour is completely absent, as in Pinot Blanc, or less blue colour is formed, giving the impression of a kind of mixed colour, as in Pinot Gris. Both have mutated from Pinot Noir and are actually one grape variety.

Pinot-Sorten - Pino Blanc, Pinot Gris, Pinot Noir, Pinot Meunier, Frühburgunder

In extreme cases, one can even find differently coloured berries on a single grape. Apparently, this mutation can mutate back again, so that one occasionally finds Pinot Blanc with grey and white grapes on one plant. Although these colour variants in blue, white or grey cannot be distinguished either by the green leaf or genotypically, they were given their own names a long time ago and treated as independent grape varieties. Of course, the different wine characteristics of the colour varieties also contributed to this. Another example are the genotypically identical "varieties" Gewürztraminer, Roter Traminer and Weißer Traminer, which only differ in the intensity of taste of the berries and the wine. Although strictly speaking they are "only" mutated clonal variants, these varietal variants are still treated as independent varieties, although all three can be assigned to the one Traminer variety.

Seedlings

This generally applied practice, however, dilutes the actually biologically quite clearly defined grape variety concept. This is because the conspicuous varietal variants resulting from clone selection are wrongly treated in the same way as the varieties resulting from seedling propagation (only these can be described as independent in the strict sense). Genotypically differentiable varieties are always selected seedlings. In practice, conspicuous clonal mutants such as Pinot Blanc or Pinot Meunier function precisely as independent varieties, although they are not seedlings of Pinot but mutants of Pinot Noir. They are externally distinguishable, but genotypically not or hardly differentiated. If the concept of variety is defined narrowly, then there would firstly be varieties in the strict sense (seedlings from generative or sexual propagation) and secondly clones of varieties that have emerged from them (mutants from vegetative propagation). In practice, however, everything that is somehow still visually distinguishable is mistakenly called an independent variety.

Propagation

In the past, mass selection was common practice in vineyards, and mutants were propagated consciously or unconsciously so that clonal diversity could develop and be maintained for centuries. Regionally and especially in climatic or zonal border areas, climate-adapted clones can be found, as for example frost (especially winter frost) always selects sharply. However, major environmental adaptations, for example to newly introduced pathogens, are not to be expected from somatic mutations, since the mutation-related clonal differences usually only change the physiology and biochemistry of the variety clones quantitatively, but not fundamentally. And adaptive changes of grapevine varieties by generative or sexual means are excluded because of the exclusively vegetative mode of propagation (in biology, adaptive means the ability of organisms to actively adapt to changing environmental conditions).

Practice clone

In modern viticulture, a practice clone is understood to be all vines that have emerged from the clone selection and testing of certain positively striking and selected individual vines (accession). These are planted in basic facilities, observed for several years and carefully tested for their viticultural properties. From these primary clones, the "best" mother vines are selected, which, after further testing and approval, are then used in nurseries as starting material for commercial mass propagation. From these, the one-year-old fruit shoots (scions) are separated, which are cut into shoots with internodes and two bud-bearing nodes each. These are grafted onto rootstocks that are resistant to vine blight. In this way, up to 50 identical offspring can be produced from a single mother plant.

These clone copies are initially genetically completely identical to the mother vine, but can also accumulate mutations over the decades. These young mutations in the vineyard, however, are no longer relevant for breeding, as clone selection is no longer practised in modern farms, which are mostly built up from only one variety clone and are grubbed up again after 30 years. In the wine-growing countries, clone breeding is strictly regulated and officially controlled. Each clone receives a breeding number and must be officially recognised (like a new grape variety) for the production of quality wine. The absence of viruses in the breeding material is one of the essential requirements for approval. In France, for example, there are about 50 recognised clones of Pinot Noir, with quite different characteristics in detail.

Clones in nurseries

As a rule, different clones of grape varieties are available in the nurseries. However, they often differ only marginally in a slightly higher yield, which can only be measured over the years, or in a slightly higher sugar yield. These mass clones, mostly selected for maximum yields, do not reflect the actual developed clonal diversity of a grape variety, which can be quite considerable in old varieties with regard to morphological, biochemical and genetic differences. Due to the commercialisation of vegetative vine propagation in nurseries and the one-sided focus on a few practical clones, the clonal diversity of most varieties has already shrunk to a few surviving specimens, which are also frequently viral. This means that all vines in a vineyard are descended from a single mother plant and are genetically identical. But it is increasingly common again to use different variety clones in a vineyard in order to achieve a certain spread of risk. See also under DNA, clone selection, mutation, vine certification and breeding, and a list of relevant keywords under grapevine.

Pictures: Ursula Brühl, Doris Schneider, Julius Kühn-Institut (JKI)

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Dr. Christa Hanten

For my many years of work as an editor with a wine and culinary focus, I always like to inform myself about special questions at Wine lexicon. Spontaneous reading and following links often leads to exciting discoveries in the wide world of wine.

Dr. Christa Hanten
Fachjournalistin, Lektorin und Verkosterin, Wien

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