Agriculture Reference
In-Depth Information
The grapevine belongs to plants, in which a the existence of a very strong relationship between
ABA produced in drought-exposed and stressed roots on the one hand and quality of grapes
on the other.
Abscisic acid (ABA) is therefore the most important plant hormone that influences ripen‐
ing and quality of grapevine berries. The participation of ABA is high at the beginning
of development of berries and decrease till the period of berry softening. Its content in‐
creases again during the initial stages of accumulation of sugars and reaches the maxi‐
mum approximately 2-3 weeks later (Davies & Böttcher, 2009). The content of ABA in
the skin is higher than in the pulp (Coombe and Hall, 1973). Also grapevine seeds con‐
tain more of this acid than pulp (Zhang et al., 2003). ABA participates also in biosynthe‐
sis of anthocyanins and, according to Davies & Böttcher (2009) in the accumulation of
sugars in berries. Drought-induced stress supports the formation of ABA and show a
positive effect on the formation of secondary metabolites, above all of flavonoids, which
involve anthocyanins and tannins. Under conditions of water stress, concentrations of an‐
thocyanins and proanthocyanidins in the skin increase independently on the size of ber‐
ries; this process is dependent above all on the availability of water (Roby et al., 2004).
In grapevine plants suffering from drought-induced stress, the synthesis of reserve substances
may be impaired due to an inhibited photosynthesis. This means that the plants are not
adequately prepared for overwintering. This stress markedly influences the quality of grapes.
Contents of amino acids, organic acids and also sugars are usually reduced. Stressed plants
show a decreased uptake of minerals from soil and, thus, lower extract in wine. In extreme
cases it is possible to observe negative effects on smell and taste of wine as well as the
occurrence of the ATA phenomenon (atypical aging - ATA). Due to a high content of poly‐
phenols, the taste of stressed wines is bitter, disharmonic and „short“.
From the viewpoint of quality of harvested gapes, a proper evaluation of the drought-induced
stress risk is very important. In white wine varieties, this type of stress may show more negative
effects than in varieties used for making of red wines because in this case the synthesis of ABA
may show a positive effect on formation of phenolic substances.
4.2. Tolerance to drought in wild species and rootstocks varieties
The use of rootstocks makes it possible to give plants a certain capacity to adapt drought
conditions. A good knowledge of tolerance of rootstocks is important above all with re‐
gard to the use of these genetic resources in the process of breeding and selection of
plants tolerant to drought.
The capability of plants to create a root system efficiently penetrating into the soil is an
important factor, which enables them to survive during longer periods of drought and
water-stress.
The assessment and evaluation of tolerance of rootstocks to drought represents an important
component of the process of selection of suitable rootstocks and for further breeding work.
The classification of rootstocks into five groups according to their tolerance to drought is
presented in Table 5 (Carbonneau, 1985).
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