Introduction

Most of the well-known grapevines belong to
the Vitis vinifera species which are
of great value for their fruits and fermented products. There is evidence that grapevine
culture begun as far back as the Neolithic period (Roderick, 2000) while viticulture is
of great economic importance for many countries. Those plants produce only one
crop of fruit each growing season, thus it is of great importance to select and
cultivate only the variants that produce more and better grapes.  

A number of propagation techniques are
available for the grower, which include germination or planting a new cutting
that has been selected by either clonal or mass selection (Vine, 1997). Choosing the most result-
and cost- efficient method is more than crucial for the grower’s company viability
and this is the subject that we are going to discuss on this assignment.

Vitis vinifera (Grapevine) Botany

Plants of Vitis vinifera
species (European grapevine) are well-known for their delicious crops of fruit
which can be consumed fresh or dried but also for making wine. Furthermore, the
vine is used for ornamental purposes only as well as for providing shade during
hot summers.

Although they were native to regions expanding from around the
Mediterranean Sea (Spain, Italy, Greece, Asia Minor, North Africa), up to the
Caucasus, the grape is now grown almost everywhere in the world.  They are plants that can grow well on almost
any kind of humus-rich soil, with medium to low water requirements, but they
need good drainage, full sun and pruning once or twice a year.

Classification-Taxonomy

The European grapevine is classified in the genus Vitis, which is
classified in the family Vitaceae in the major group of Angiosperms (Flowering
plants). Its detailed classification is given below: (Vitis vinifera – Wiki)

Kingdom:            Plantae

Clade:                   Rosids (Eudicots,
Angiosperms)

Order:                   Vitales

Family:                 Vitaceae

Genus:                 Vitis

Species:               Vitis vinifera

Structures and Anatomical Characteristics

Vitis vinifera species are woody perennial vines (liana)
whose trunk length can reach up to 35m, although in the pruning stage it only
measures between 1- 3m high. Its leaves are dull green on the upper face and have
a gray tone on the lower face. Their diameter is 5-23cm and they have thin, circular
or oval shape, toothed or slightly dented on the edges, with 4-5 lobes.

Grapevine’s flowers are arranged in clusters, opposite to the leaves and
they produce a fruit, called grape. The grape is technically a berry and its pulpy
roe is small (diameter: 6-12mm), of various shapes (circular, oblong, etc ) and
colors (green, reddish, dark red, etc.) depending on the variety. (Misouri
Botanical Garden)

Sexual and Asexual Plant Propagation

Plant propagation is the production of new plants which is achieved,
depending on the kind of plant of interest, by sexual and/or asexual
proliferation. The use of each method has advantages and disadvantages that
should be taken into consideration in advance, in order to achieve a cost competitive
production (a lot of new, healthy and productive plants) (Toogood, 1999).

Sexual propagation involves contribution of both female and male gametes
for creation of new plants, through flowering, pollination, fertilization (in
vivo or in vitro) and seed formation to be sown for new plants to grow. Those
new plants will be genetically different from the original plants, following
the Laws of Heredity.

Asexual Propagation, on the other hand, is the production of new plants
genetically identical to the originals (clones), through vegetative parts of
the plants. Asexual propagation techniques include (Mauseth, 1988) (Lacy & Kaufman, 2006):

v  Propagation by cuttings: Parts of plants are cut from a parent plant and inserted into an
appropriate medium (water, sand or soil-less mixes) where they form roots becoming
new plants.

v  Propagation by division: New plants are separated from the parent plant. Division methods vary
widely and are considered one of the easiest methods of propagation even for
amateur gardeners.

v  Propagation by layering: Roots are assisted to form on stems that are still a part of the parent
plant, by bending and covering branches with soil, while keeping it on place
until new roots have formed. Then the new plant is reperated from the old one.

v  Propagation by crafting or budding: Grafting is any process where a scion (part from
a plant), is made to unite with another plant (called the stock). The purpose
of this method is to either increase the chances of the scion plant to grow
successfully, or to change over the form, character, productivity etc. of the
stock plant.

v  Propagation by tissue culture (micro-propagation): This high-tech method uses
non-differentiated plant cells to regenerate a new plant. Those cells are
cultivated on a culture media (e.g. agar) given the required nutrients and
plant hormones (George, 1993).

Grapevine Propagation Methods

While grapevine’s wild type ancestor (Vitis vinifera sylvestris) has
dioecious flowers (male and female flowers on separate plants), domesticated
vines have hermaphrodite flowers (male and female flowers on the same plant).
Pollination is required for the fruit to develop by sexual proliferation.
Despite this, commercial viticulture rarely uses vines propagated from
seedlings because each seed contains new genetic information derived from
unique gene combinations which occurred during fertilization. This sometimes
can lead to the production of a new variety starting from gametes produced by a
plant of a given variety (Tornqvist, 2006). Thus, asexual means of propagation is
preferred in viticulture.

Hardwood cuttings, which are most commonly taken during the winter
months, are generally used in propagating plants of commercial value. The way
that a vine grower selects these cuttings can be described as either clonal or
mass selection. Each cutting taken from a vine is a clone of the original plant,
meaning an exact replica of the mother vine. In clonal selection, a plant that
has exhibited the most desirable traits in the nursery or the field is selected
and all cuttings are taken from this. In mass selection, cuttings are taken
from several vines of the same variety that have collectively demonstrated
desirable traits. The second method ensures a touch of diversity in
viticulture, something that can prove very important for its viability.  (Roby, Leeuwen , Gonçalves , Graça , & Martins ,
2014)

Furthermore, propagation by crafting or layering can be used in special
cases. Propagation by crafting is a quick and relatively inexpensive way of
quickly changing over a vineyard from one hardy variety with a strong rhizome
to another more desirable one. In this way the newly crafted plant is usually
able to start producing a crop by the next growing season. In case a plant is
lost due to a disease or other damage and if only a few vines need to be
replaced within a row, layering will be used to regain the lost plant. (Propagation_of_grapevines – Wiki)

Plant Growth Regulators, Auxins and Hormones

Plant hormones are endogenous cell compounds with a regulatory role in plant growth
and fruit ripening. In general, plant growth substances are categorized into five (5) major groups,
each of which has a
specific function.

Those groups are:

(a)
Auxins
and (b) Cytokinins: Auxins and Cytokinins (natural or
synthetic) usually work together and are by far the most important for
regulating plant growth and morphogenesis. Auxins are compounds that positively
influence cell enlargement, bud formation and root initiation. They also
promote the production of other hormones. Cytokinins are a group of chemicals
that influence cell division and help delay senescence of tissues. Auxins together
with Cytokinins, they control the growth of stems, roots and fruits, and also convert
stems into flowers.

(c)
Gibberellins: Gibberellins are important in seed germination. They also promote
flowering and cellular division.

(d)
Ethylene: Ethylene forms
through the breakdown of methionine in plant cells. Its effectiveness as a
plant hormone depends on its rate of production, versus its rate of escaping
into the atmosphere. Ethylene affects cell growth and shape (stem diameter and
height) as well as fruit-ripening.

(e)
Abscisic acid: Abscisic acid acts as an inhibitor that affects bud growth, and seed.

 (Plant hormone – Wiki)

The appropriate use of Plant growth regulators is widely used in modern
horticulture, because many plant processes can be actively regulated. For example, acceleration or delay
of seed germination, induction of flowering and fruiting, acceleration or delay of senescence
processes including fruit ripening and defoliation. The achieved benefits range
from facilitating crop management to increasing and securing yield and quality
of the production as well as improving
its storage and shelf life. (Rademacher, 2015)

Grapevine Growth Regulators, Auxins and
Hormones

Grape and wine production is
extremely dependent on the fruit ripening process which is under complex
hormonal control. An overview of the roles of abscisic acid and ethylene as
promoters of ripening, as well as the role of auxins, cytokinins and
gibberellins as inhibitors of ripening are shown in Figure 1. (Fortes, Teixeira, &
Agudelo-Romero, 2015)

Fig.1 Overview of the main events
involved in the hormonal control of grape development and ripening

 (Fortes, Teixeira, & Agudelo-Romero, 2015)

Considering the data given we can easily understand that any well
informed grower is able to control his production growth and ripening to suit
his needs.

Major conclusions
and recommendations

For a grower with entrepreneur interests what matters the most is the
yield per unit ratio, meaning how much useful crop he can generate with minimal
cost. It is already mentioned that for recreational agricultural purposes there
are various propagation methods. However for any company to achieve
profitability, the revenues have to be higher than the expenses. This can be
achieved by selecting the most cost effective growing method, as well as the
appropriate variety that is best suited for the climate and the grower’s needs.
Those are the first vital steps toward profitability. (David Tilman, Cassman, &
Matson, 2002)

Grapes grown for any kind of production (especially for fresh fruit) are
high maintenance plants that require regular pruning and ongoing attention to
insect and diseases……………..