Offspring (grassy twig or rice) produced by asexual reproduction from an organism. In humans, identical twins form a natural clone. In plants, this is called vegetative reproduction, when new plants are regenerated from certain tissue parts of a parent plant. In the process, genetically completely identical organisms with hereditary characteristics are 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, only after a certain amount of morphological and genetic change can one speak of mutants. In the so-called somatic chimeras, the mutations occur in a tissue-specific manner, i.e. the outer epidermal cells may have one or more mutations, but these have not occurred in the inner cell layers, or vice versa.
Such chimeras should even be the rule with the vine, because with the first divisions of the embryo the principle division of the tissue layers into epidermis and inner cell layers is deterministically fixed forever. This dichotomy of the basic tissues is already contained in every newly formed axillary bud, so that chimerisms are also multiplied during vegetative propagation via cuttings. On the other hand, in sexual reproduction two parent varieties are crossed, so that from each fertilized seed a new vine variety grows, half of which has the newly combined genetic material of both parents. This is how new grape varieties are created through targeted cross-breeding by sexual reproduction. However, somatic mutations and vegetative propagation result in clone variants, mutants and chimeras.
Clone, mutant and clone mutant
The terms clone, mutant and clone mutant are often used colloquially to mean the same thing in viticulture, but this is not correct, because a clone in the strict scientific sense is an identical copy of the original, whereas a clone in the viticultural sense is a mutated clone variant and is no longer 100% identical to the original plant. In practice, clones of grape varieties are only addressed as clones if they can at least be easily distinguished from the original type in some visible or measurable individual characteristics, i.e. if they are already mutated. Such mutations occur spontaneously and frequently as bud mutations. Later after budding, they are multiplied by vegetative propagation of the mutated shoots.
A clone mutant is a clone (duplicate) of a variety which deviates in some characteristics. Clone mutants are created by spontaneous mutation of a fruit shoot which was selected for its abnormal characteristics and further propagated vegetatively. However, it is a somewhat imprecise term, the boundaries between clone (which strictly speaking means a 100% duplicate), clone mutant and mutant are fluid. In simple terms, clone mutants can be characterised more by shifts in quantitative characteristics (higher must weight, lower yield, stronger growth) than by clear visual distinctions based on qualitative characteristics (berry colour/form, leaf hairiness, early maturity). The Pinot varieties Blauer Arbst, Frühburgunder, Pinot Liébault, Pinot Mariafeld, Pinot Tete de Negre, Pinot Teinturier and Velvet Red are often referred to differently as clone, clone mutant, mutant, biotype or variety.
Grape variety clones/mutations
These mutants can mutate again and develop into independent mutation lines. Thus, especially in old, widespread and millionfold multiplied varieties such as Chasselas, Pinot or Traminer, several regional lines of descent with independent grape variety clones have developed. Very striking 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 like 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 colorants) that determine berry color are biochemically produced in the cells in a chain of synthesis steps. This chain is interrupted by one or more mutations in the underlying genes, so that fewer colour pigments or only the colourless precursors are produced. As a result, either the colour is completely absent, as in Pinot Blanc, or less blue colour is produced and the impression of a kind of mixed colour is created, as in Pinot Gris. Both are mutated from the Pinot Noir and actually it is a grape variety.
In extreme cases one can even find differently coloured berries on a single grape. Apparently this mutation can mutate back again, so that occasionally Pinot Blanc with grey and white grapes can be found on one plant. Although these colour variants in blue, white or grey can neither be distinguished on the green leaf nor genotypically, they were long ago given their own names and treated as independent grape varieties. The different wine characteristics of the colour varieties naturally also contributed to this. Another example are the genotypically identical "varieties" Gewürztraminer, Red Traminer and White Traminer, which differ only in the different taste intensity of the berries and the wine. Although strictly speaking they are "only" mutant clone variants, these variety variants are still treated as independent varieties, even though all three can be assigned to one variety of Traminer.
However, this generally applied practice dilutes the actually biologically quite clearly defined vine variety concept. This is because the conspicuous variety variants resulting from clone selection are wrongly treated in the same way as the varieties resulting from seedling propagation (only these can be considered independent in the strict sense). Genotypically differentiable varieties are always selected seedlings. In practice, conspicuous clone mutants such as Pinot Blanc or Pinot Meunier function as independent varieties, although they are not seedlings of Pinot but mutants of Pinot Noir. Although they are outwardly distinguishable, they are not or hardly differentiated genotypically. If one were to define the term "variety" narrowly, then there would be varieties in the strict sense (seedlings from sexual reproduction) and secondly variety clones (mutants from vegetative reproduction). In practice, however, everything that is somehow still visually distinguishable is erroneously called an independent variety.
Reproduction
Through the mass selection (mass selection) in the vineyard, which was common in earlier times, mutants were consciously or unconsciously propagated, so that clone diversity could develop and be preserved over centuries. Regionally and especially in climatic or zonal borderline locations, climate-adapted clones can be found, since frost (especially winter frost), for example, always selects sharply. However, somatic mutations are not expected to lead to greater environmental adaptations, for example to newly introduced pests, since the mutation-related clone 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).
In modern viticulture, a practice clone is understood to be all vines that have emerged from the clone selection and testing of specific, positively conspicuous and selected individual vines (accession). These are planted in basic plants, 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 the basic material for commercial mass propagation. The annual fruit-rods (scions) are separated from these and cut into shoots with internode and two bud-bearing nodes each. These are grafted onto phylloxera-resistant rootstocks. In this way up to 50 absolutely 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. However, these young mutations in the vineyard are no longer relevant for breeding, as clone selection is no longer practised in modern vineyards, which are usually built from a single clone of a variety and cleared again after 30 years. In wine-growing countries, clone breeding is strictly regulated and officially controlled. Each clone is given 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 very different characteristics in detail.
Several different clones of grape varieties are usually available in the nurseries. However, they often differ only marginally, for example in a statistically only over the years measurable, slightly increased yield or a slightly higher sugar yield. These mass clones, mostly selected for maximum yield, do not reflect the actually developed clone 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 vine nurseries and the one-sided orientation towards a few practical clones, the clone diversity of most vine varieties has already shrunk to a few surviving specimens, which are also often virulent. This means that all vines in a vineyard are derived from a single mother plant and are therefore genetically identical. But it is slowly becoming common practice again to use different clones of one variety in a vineyard to achieve a certain spread of risk. See further information under the keywords DNA, mutation, certification of vines and breeding.
See pictures: Ursula Brühl, Doris Schneider, Julius Kühn Institute (JKI)