In the European and Italian areas, the major news in vine growing comes from the attempt to introduce in a significant way the seedless varieties in the market, in order to answer the increasingly attention given by consumers to this characteristic.
The seedlessness in grapes consists in the production of acinus without seeds: the term comes from the word apirenia, that in Greek means seedless. From a botanical point of view, the seedlessness is a natural phenomenon that leads to the formation of acinus without seeds and, consequently, smaller compared to acinus with seeds; these grapes are known on the market in different ways, such as seedless grapes, grapes without seeds, uvas sin semillas.
Traditionally, the seedless grape was always assigned to the drying process for the production of raisin, known also as Sultanine grape.
In the latest years, seedless grapes are becoming very important from a trading point of view also for the consumption of fresh grapes with the traditional seeded grapes.
In some countries the request for seedless grapes has even exceeded that of seeded grapes: this nice natural feature of the table grape is radically modifying consumers’ tastes, who as well as in grape, appreciate seedlessness also in other fruits, such as Clementine, kiwis, watermelons and persimmon.
The seedlessness is appreciated for different reasons: the ease with which children can eat grapes, the absence of embarrassment when people need to expel seeds out of the mouth, the ease in preparing sweets and fruit jams, the ease in preparing fruit assigned to the fourth range.
There are traditionally two types of seedlessness:
- Stenospermocarpy (fruit with rudiments of seeds) defined as Sultanine type;
- Parthenocarpy (fruit without seeds) defined as Corinto type.
All the seedless grapes traded for fresh consumption, belong to the group of stenospermocarpic grapes; the section of their berries have, in different shapes, rudiments of aborted grapeseeds. In this grapes, the physiological process involves the pollination of the flower, the fecundation and the following abortion of the seed. The acinus stops early the development and the berry remains small. The short survival period of the small seed during the growing phase is enough to set the berry and to produce stimulating hormones of growth (cytokinins, gibberrelins). When the embryo dies stops also the action of the hormones and for this reason the berry's development is limited. Abortet seeds (grapeseeds) atrophy and only small rudiment of different thickness, from herbaceous to semi-ligneous, remain.
To this group belong the traded seedless varieties: Early Red , Early Gold , Regal , Sugraone , Perlon , Centennial , Thompson, Crimson, etc. However, the traded seedless grapes are not completely without seeds, and therefore they should be defined"grapes with non-visible seed”: this aspect can be seen also in other fruits, for example in some new varieties of “seedless” watermelon there are atrophied seed that are whitish.
The berries of seedless grapes are naturally smaller than those with seeds.
Furthermore, it is possible to have also in seedkess grapes larger berries only using hormones that induce the stimulus to grow, which is determined by hormones naturally produced by the seed itself. A similar action is done with the agronomic technique of the girdling, as it increases the availability of sugars and hormones that enhance the growth of berries.
The actors of the vine growing environment, such as producers of grapes, retailers of grapes, wholesalers of grapes, importers of grapes and exporters of grapes ask for acinus as large as those of seeded grapes, considering that, only in this way seedless grapes can become really popular in the table grape market, without considering, however, that seedless grapes, for biological reasons are smaller.
The seedlessness in table grape is however a natural feature: one of the goals of the genetic improvement of grapes, therefore, should be to enhance something that nature already has and not to obtain, at any cost, seedless grapes with large berries, with genetic manipulations.
Particularly interesting are also the earliness, because early grapes can be placed in a better way on the market, quality characteristics of grapes, that are the regular appearance of the cluster, the larger size of berries, the uniformity of berries and of the skin colour.
Regarding taste, the most requested characteristics by consumers of table grape are, apart from seedlessness (grape without seeds), sweetness (a good ratio sugars/acids in the juice), flavour, crunchiness, juiciness of berries, and the thin skin; furthermore the resistance to transports and preservability.
In Italy, after having spent the 2007 season consolidating foreign markets previously acquired, seedless grapes have doubled their production volume in 2008.
Among the seedless grapes cultivated in Italy, the major varieties are:
- APULIA ROSE SEEDLESS: Intense red table grape; it is the last seedless grape variety, recently created in Apulia: this late grape variety is very rich in nutritional and anti-oxidant substances, keeps very well in refrigerators with a very long shelf-life that permits also a good resistance to transports. Clusters are medium-large, cylindrical-conical, sparse, weighing on average 600/800 gr. Berries are medium, spherical and intense red, the flesh is quite hard and sweet and the acinus in general keeps well on the plant.
- AUTUMN ROYAL SEEDLESS: Seedless table grape variety more and more appreciated for the fresh consumption. It is available on the market from September until the end of November. The cluster is beautiful, not too much dense, cylindrical-conical, berries are medium (weight about 6 gr), ovoid and blue-black, with a hard and uncoloured flesh.
- CENTENNIAL SEEDLESS: Seedless, white table grape coming from California. The cluster is quite large, conical-cylindrical, winged and sparse. Berries are medium, ellipsoidal (quite elongated), with a neutral and sweet flavour-; the skin is dark yellow, slightly pruinose and thin and the pulp is fleshy and seedless. This variety of grapes is available on the market from the end of July to mid-September.
- CRIMSON SEEDLESS: Red-violet table graps, characterized by unique organoleptic qualities and appearance, for which this variety is very appreciated by consumers. It is a variety that keeps very well and is available from September to December. The cluster is medium-large, weighing about 500/600 gr and shouldered. Berries are elongated, intense red; the flesh is hard and crisp and very palatable.
- DAWN SEEDLESS: Seedless table grape vine, obtained in Davis, California by Prof. H. P. Olmo by crossbreeding Gold with Perlette. It has a good production level and is of good quality, above all for the flesh, which is crisp and for the yellow skin. The acinus is medium (3/4 g.) and ellipsoidal. The cluster is quite big, shouldered cylindrical, semi-dense, weighing on average around 700 gr. It ripes at the end of July-beginning of August.
- EARLY GOLD®: Seedless, white variety that has been recently created in Argentina. The cluster is medium-large, shouldered, weighing about 600 gr, simple and quite sparse; the acinus is medium-large, seedless, yellow-green weighing on average 5-6 gr., the flesh is crisp, juicy and sweet. The vine is very vigorous and has a high production level with a fertility level of 1.4. The production of grapes of this variety is high and costant.
- SEEDLESS FIESTA:White, seedless variety of grapes, very sweet, used above all for the production of raisin
- SEEDLESS MELISSA: It is a seedless grape variety, obtained in California by D. Ramming and R. Tarallo, patented with the name Melissa and later renamed Princess seedless. It is a variety with cylindrical, light green berries with a slight flavour of muscat. It ripes at the same time of the variety Thompson. Since a few years, it has been cultivated in Italy as an experiment in some wine making companies of Apulia. It is a variety of white table grape, very productive, characterized by its beauty, the size of its berries and the great storage capacity in the refrigerator and on the plant. It is available on the market starting from the end of August. The cluster is medium-large, conical and not too much dense. Berries are large, cylindrical-ellipsoidal, the flesh is crisp with a palatable flesh and a yellow-green skin.
- PASIGA: It is one of the most interesting seedless table grapes for the fresh consumption. Obtained by Dr. A. Gargiulo (Argentina) by crossbreeding Alphonse Lavallée with Sultanine. The cluster is medium-large, conical shouldered, winged, sparse, with an average weight of about 500 gr. The quality is good: in fact, together with a quite large size of the blue-black berry, the acinus weights about 4 gr and has a crisp and nicely sweet flesh. It ripes in the second decade of August.
- PERLON: Obtained by Dr. A. Gargiulo in Argentina by crossbreeding Emperor with Perlette. The seedless table grape vine is suitable both for the fresh consumption and for the industrial processing. The cluster is short-conical, semi-dense, weighing on average about 600/700 gr. The berry is medium (about 5 gr.), ovoid; the skin is violet and pruinose; the flesh is crunchy, with very small seeds and the flavour is neutral, slightly acid. It ripes at the beginning of September.
- SUGRAONE: It comes from California, where it was created by I.M. Garabanion in 1963 by crossbreeding Cardinal with an unknown seedling. It can be often confused with “Centenia". It is a seedless table vine grapes, great for fresh consumption. The grape quality is high and can therefore have high prices on the market. The cluster is medium-large, conical, sometimes winged, dense, with an average weight of 500 gr. The berry is medium (weights about 6/7 gr.), ovoid with a crisp and fleshy pulp and a slightly flavoured taste, with sugars at 14%, total acidity 4x1000, pH 3.80. The skin is yellow and pruinose. It ripes between the third decade of July and the first decade of August.
- THOMPSON SEEDLESS: Seedless white table grape, perfect both for fresh consumption and for the processing into juices and distillations. It is a variety of grape used above all to produce raisin and it is available from the end of August until October. The cluster is medium-large, cylindrical-conical, quite dense or semi-sparse, weighing about 350-450 gr. Berries are medium-small, ovoid or ellipsoidal, with a crisp flesh, simple flavour, sugary, quite palatable and a gold-yellow or light yellow pruinose skin, thin but resistant.
- VITROBLACK 1:Obtained in 1994 by “Vitroplant". It is a variety of black seedless grape, very productive and early. When completely ripe, it is black and has great organoleptic characteristics and a sugary flavour.
There are many other varieties of seedless grapes, such as BLACK SEEDLESS, BLUSH SEEDLESS, CENTENNIAL SEEDLESS, CORINA, CORRIN SEEDLESS, EARLY RED, EMPERATRIZ (RED SEEDLESS), BLACK PEARL, RED FLAME, RUBY SEEDLESS, SILCORA.