What is clonal selection theory???

Question

What is clonal selection theory???

Answer 1

Clonal selection is the practice of selecting a single superior plant in the vineyard and then taking cuttings from this vine for propagation. The selection is generally made with a particular attribute such as yield or fruit ripeness in mind. Clonal selection contrasts with mass selection.

New grapevines, in common with many other perennial crops, are produced by vegetative propagation, that is by using cuttings which are genetically identical. (This contrasts with agricultural field crops which are multiplied by seeds which are different one from another-although sexual reproduction leading to the production of seedlings is the means by which new varieties are created.) In vegetative propagation, each bud from a so-called `mother vine' essentially gives rise to a plant of the same clone (except for those very rare cases in which a bud mutation has taken place).

Clonal selection for vines was first demonstrated in 1926 in Germany where it has been most widely practised. Other European countries have also developed clonal selection initiatives, but the practice is less well developed in some countries of the New World.

Clonal selection depends on the fact that adjacent vines in a vineyard may be different, sometimes discernibly different. More often the differences can be established only after some years of careful measurement. Differences on this scale would not normally be expected from soil variation. There are two possible explanations: the first being a difference in genetic make-up between the vines due to mutations; the second being a difference in the incidence of diseases in the vines.

Sometimes the disease is `graft transmissible' and is carried from one vine generation to the next in cuttings. The most common and commercially important transmissible disease agents are viruses (see virus diseases). Such disease agents are transmitted by careless selection of the budwood or rootstock material used at grafting (and thus a human influence), but it may also reflect the effect of viruses, viroids, or phytoplasma transmitted by nematodes or insects (see insect pests). In any event, infection, especially due to a virus, can have a major impact on yield, fruit ripening, and wine quality.