Use of gibberellins in viticulture. Effects of Phytoregulators and Hormones in the Vine.
Gibberellins are a group of natural plant hormones capable of regulating important physiological phenomena in plants, including those that lead to growth and proper seed formation.
To date, more than 130 different types of gibberellins have been identified in plants , fungi, and bacteria, although only a small fraction possess biological activity (Thomas et al. 2005).
Due to their regulatory capacity, these hormones have been used in agriculture for decades to optimize the growth of different plant species and improve certain quality traits.
The first studies aimed at evaluating the interest of its use in the production of table grapes and wine grapes already indicated its potential to increase crop yield, advance the flowering and ripening date, and generate looser bunches in typically compact varieties. , which generates an improvement in the quality of the grape, hinders the development of fungi and unwanted pests, and facilitates the management of the vineyard (Weaver 1960).
Today, its use is widely standardized in viticulture , being used very commonly to regulate production, increase the size of grapes (which increases their commercial value) and / or promote the formation of seedless grapes (apirenas grapes). in various varieties of table grapes.
The effect of gibberellins on the vine depends on the variety of vine, the dose used and the time of application:
1 – If used before flowering , gibberellins have proven to be an effective measure to reduce the compactness of the cluster of compact varieties, being a useful strategy for both wine grape varieties [eg: Sauvignon blanc or Zinfandel (sin. Primitivo)] (Figure 1) and for table grape varieties (eg: Thompson seedless) (Miele et al. 1978, Molitor et al. 2012, Weaver and McCune 1962).
According to these studies, the reduction in compactness is due to the elongation of the rachis, which gives rise to a greater space for the distribution of the berries, generating a looser and more airy architecture.
2 – If applied in full bloom, they can be an effective measure to increase flower drop in the inflorescence, which will ultimately reduce the number of berries in the bunch and, consequently, their compactness.
This practice turns out to be useful both in wine grape varieties (eg: Pinot noir, Pinot blanc, Pinot gris) and in table grape varieties (eg: Crimson seedless) (Dokoozlian and Peacock 2001, Evers et al. 2010 ).
3 – Post-flowering : the application of gibberellins during the first weeks of berry development is the most used technique to increase the size of the fruit in apirena varieties (Casanova et al. 2009) (Figure 2).
In this type of vine varieties, after pollination an early degeneration of the seeds occurs, which in varieties with seeds are the main natural source of gibberellins. Thus, the exogenous application of this hormone will partly replace its absence, being able to obtain fruits with a commercially acceptable size and without seeds (Pérez et al. 2000).
More information on the use of gibberellins in viticulture:
Grapes farming. Application of GA3.