Grape Breeding Tasks

Due to the fact that in the past the grape assortment in most vine-growing regions of the USSR was selected at random, and also owing to the penetration of phylloxera and fungal diseases into a number of our regions and the emergence of new requirements associated with socialist construction, the issue of selecting new grape varieties and replacing old ones is currently acute in most areas.

Regional Tasks of Grape Breeding

In order to understand what specific tasks of grape breeding are currently faced in the Union, it is necessary to briefly list them by individual regions:

• Dagestan ASSR: Improvement of local table varieties and selection of new ones; breeding of wine and table export varieties with a short vegetative period.
• Crimean ASSR: Selection of varieties for the steppe part of Crimea; obtaining muscats resistant to oidium; obtaining productive, high-quality black varieties for the southern coast; improvement of standard varieties in the direction of increasing productivity.
• Central Asia (Turkmen SSR, Uzbek SSR, Tajik SSR): Selection and breeding of high-quality, winter-hardy table and wine varieties for cultivation without winter covering; selection and breeding of drought-resistant, high-quality table and wine varieties for cultivation on unirrigated (bangar) and semi-bangar lands; breeding of large-fruited, productive, and high-quality seedless varieties for drying; improvement of the Nimrang variety and selection of new transportable varieties with a hermaphroditic flower structure; breeding of salt-tolerant varieties; breeding of varieties resistant to cercospora and oidium.
• Ukrainian SSR and Moldavian ASSR: Obtaining high-quality, winter-hardy varieties for cultivation without winter covering; obtaining high-quality varieties resistant to mildew and phylloxera; obtaining varieties of early ripening and late bud burst.
• Transcaucasia (Eastern and Western Georgia, Azerbaijan, Northern Armenia): In connection with the infestation of the region with fungal diseases, especially in Western Georgia, it is necessary to breed varieties resistant to mildew and oidium; breeding of phylloxera-resistant, as well as fungal disease-resistant high-quality wine varieties; breeding of rootstock varieties that do not suffer from the leaf form of phylloxera and are adapted to local soil conditions; obtaining high-yielding high-quality varieties, such as Tavkveri, but with a hermaphroditic flower; selection of table varieties of different ripening periods.
• Transcaucasia (Southern Armenia, Nakhichevan ASSR): Selection and breeding of table varieties by ripening periods and wine varieties, against the background of new cultural practices.
• Black Sea Coast (Abkhazia, Adjaristan): Due to the large amount of rainfall and the spread of fungal diseases, the main task here is to provide stable table varieties (for resorts) and wine varieties; the second, more difficult task is to provide high-quality table and wine varieties resistant to phylloxera and fungal diseases.
• Ordzhonikidze and Azov-Black Sea Krais: Obtaining high-quality varieties that are winter-hardy and feature late bud burst; obtaining varieties for cultivation on the Don sands; breeding of varieties resistant to phylloxera and fungal diseases; breeding of salt-tolerant varieties; obtaining phylloxera-, mildew-, and winter-hardy high-quality varieties.
• Northern and New Regions in the East: Selection of table varieties and varieties for processing; breeding of winter-hardy varieties with a short vegetative period.

Based on this brief list of the main breeding tasks in individual regions, it is evident that many of them are repeated. However, the indicated regions differ from one another so significantly that obtaining a single variety in one place to satisfy the needs of all regions is impossible. This is why, for the resolution of local tasks, a breeding unit exists in almost every large grape region, working in the direction of breeding or selecting varieties that meet local requirements. Currently, the institutions conducting grape breeding in the USSR include the Viticulture Section of the All-Union Institute of Plant Industry (VIR) at its Central Asian station and Sochi point, the Kirovsk station in Magarach, the Ukrainian Institute of Viticulture, the Georgian Viticulture Institute, the Uzbekistan Zonal Station in Samarkand, the All-Russian Institute of Viticulture in Novocherkassk, the Anapa Experimental Station, the Michurin Central Genetic Laboratory, and the Far Eastern Station of VIR.

Parent Material for Breeding

Of all the ten genera constituting the family Ampelideae, only the genus Vitis is of practical interest. Representatives of other genera sometimes possess ornamental significance, and in some cases, their fruits are quite edible, as for instance, in certain species of Ampelopsis, Cissus, and Tetrastigma. They are all immune to phylloxera and mildew. However, it is impossible to use these forms in breeding due to the lack of affinity during hybridization and grafting with our cultivated grape.

The genus Vitis is divided by systematists (Planchon) into two subgenera: Muscadinia and Euvitis. This subdivision is justified not only by morphological differences but also by difficult crossability and differences in chromosome numbers. Approaching the breeding characterization of the species of these two subgenera, we proceed from the principle of geographical localization of these forms. On this basis, we divide all grapes into two main groups: grapes of the New and the Old World. The geographical isolation of these two groups led to a divergence in their fundamental properties. Most species of the New World grape acquired varying degrees of resistance and, in some cases, immunity under the influence of natural selection, whereas all species of the Old World proved completely susceptible to both phylloxera and fungal diseases. Based on the parent material for breeding, we divide grapes into four groups:

1. The first group includes Vitis rotundifolia, belonging to the subgenus Muscadinia. This species is strictly localized in the southern Atlantic states of North America and was introduced into cultivation relatively recently (at the beginning of the 18th century). The main positive property of this grape is its absolute immunity to phylloxera and mildew. Its main disadvantages are the small size of the cluster (up to 10 berries) and uneven ripening, which is already being corrected by breeding. These achievements, as well as successful crosses of V. rotundifolia with V. vinifera and the sufficiently high cold hardiness of V. rotundifolia, provide great hope for using this species in breeding for mildew and phylloxera resistance in the USSR.
2. The second group consists of American species of the subgenus Euvitis. Out of 18 species of this group, the following had practical significance: V. aestivalis, V. Berlandieri, V. candicans, V. cordifolia, V. Labrusca, V. Lincecumii, V. monticola, V. rupestris, V. cinerea, V. riparia, V. Bourquiniana. In America, some of these species were cultivated in their pure form for fruit. In Europe, V. riparia, V. rupestris, V. Berlandieri, and others played a major role as rootstocks. But their primary significance was as parent material in crossbreeding to obtain "direct producers" in America and Europe. The basic properties of these species are as follows: their fruit quality is low, mostly with an unpleasant flavor ("foxy" flavor). A certain exception in this regard is V. Labrusca, which yields good table grapes (Isabella, Lydia, etc.). The main valuable asset of these species lies in their significant phylloxera resistance.
3. The third group comprises 11 Asian species, of which V. amurensis Rupr., growing wild in Manchuria and the Far Eastern Krai, is of the greatest practical interest. This species has not yet entered cultivation, although its fruits in the forest are exploited by the local population in fresh form and for wine. The chief value of this species lies in its exceptional cold hardiness. It withstands forty-degree frosts. Disadvantages of this species include the relatively poor quality of its fruit (acidity of 25 pro mille) and susceptibility to phylloxera and mildew. It can be used locally by selecting the best forms into cultivation and by crossbreeding it with other species.
4. The fourth group covers a single species, Vitis vinifera L. To this group belongs the entire diversity of forms of the cultivated and wild so-called European grape, yielding fruits of high quality but susceptible to phylloxera and fungal diseases. The number of cultivated varieties of V. vinifera runs into thousands. To understand the full diversity, one must add a large number of wild forms growing in the gorges and mountains of the Caucasus, Kopet Dag, and Tien Shan.

The main bulk of both cultivated and wild grape forms is centered in Central Asia, Transcaucasia, and Iran, which are considered the center of diversity and origin of the cultivated grape. In Central Asia, there is a large local assortment (about 150 varieties). A characteristic feature of this assortment is a large berry, a predominance of white coloration, low acidity, and all other qualities inherent to table grapes. This direction of the Central Asian assortment is partly explained by the historical absence of winemaking, which was prohibited by Islam. The study of wild grapes of Central Asia gave highly interesting results regarding color, size, and shape of berries and clusters, productivity, and other properties. The sugar content and fruit quality of some wild forms exceed those of many cultivated forms. In this respect, the wild grape of Central Asia is of great interest to breeders, as many forms can be directly introduced into cultivation, and some can be used for hybridization.

Forms of Transcaucasia represent exceptionally high value from a breeding perspective. The local numerous assortment is strictly specialized (for wine) and localized in separate districts. Completely different varieties are found in Kakheti, Imereti, Guria, Mingrelia, Abkhazia, Azerbaijan, in the regions of Mountainous Karabakh, and other areas. Many of the surviving local grape varieties of Transcaucasia passed natural selection against phylloxera and mildew and revealed sufficient resistance to these parasites. For the breeder, some varieties of Western Georgia (Tsolikouri, Tsitska, and Abkhazian varieties) represent great interest regarding mildew resistance. In terms of phylloxera resistance, certain Kakhetian varieties stood out (Mtsvane, Rkatsiteli, etc.), which are damaged by phylloxera but die significantly later than all other varieties.

Brief Characterization of the Grape as an Object for Breeding

In nature, the grape reproduces by means of seeds and natural layers, which contribute to the spread of a single thicket sometimes over a fairly large space. In cultivation, the grape propagates vegetatively by cuttings, grafting, and layers. Consequently, according to breeding methodology, the grape belongs to the group of vegetatively propagated plants. Grape varieties represent either clones, if they were obtained by vegetative propagation from a single plant or shoot, and all their plants constitute one genotype, or a mixture of clones, if they include several genotypes, which can occur from contamination of the clone by mutations, accidental admixtures of other closely related varieties, etc. As studies of recent years have shown, most old grape varieties represent mixtures of clones.

Hermaphroditic grape varieties self-pollinate and cross-pollinate easily, and therefore are facultative self-pollinators. Their pollen is very small in size (6 microns), dry, and carried by the wind. Insects do not play a significant role in the cross-pollination of grapes. Due to the presence of a greater number of chances for fertilization with its own pollen rather than foreign pollen, some authors (Oberlin, Gard, Ziegler, Korzhinsky, Sartorius, etc.) are inclined to consider hermaphroditic varieties as self-pollinators. Branscheidt in an experiment obtained even a larger yield of berries during self-pollination of varieties than during their cross-pollination. In some varieties, pollen maturation and self-pollination are observed before the discarding of the cap (cleistogamy). All this suggests that in hermaphroditic varieties, self-pollination does indeed occur quite frequently.

Grape varieties with a functionally female flower structure in most cases have sterile pollen, due to which they are obligate cross-pollinators. Sterility of pollen in grapes is known of three types: 1) pollen sterility of functionally female varieties, where the division of pollen mother cells up to the formation of tetrads proceeds correctly, but degeneration of the vegetative and generative nuclei occurs in the microspores; 2) facultative sterility, inherent to a greater or lesser extent, depending on the conditions of the year, to all varieties; 3) hybrid sterility, known in grapes so far only in one case in hybrids of V. vinifera and V. rotundifolia, but not yet studied in detail. Sterility of the female gametophyte in grapes is known of two types: 1) obligate, as for example, in Korinka, Kishmishes, and other seedless varieties; 2) facultative, manifesting itself to one degree or another in almost all varieties. Physiological sterility (incompatibility, intersterility) of the type found in cherries, plums, apples, and other fruit crops is unknown in grapes. Crossability in grapes within the entire group is very easy. Interspecific crosses succeed as easily as intervarietal ones. The chromosome number of different grape species is 2n = 38. Deviations are found in the varieties Sultanina gigas, Muscat gigas, and Muscat Canon Hall, which represent tetraploids (2n = 76). Fruiting upon sowing grape seeds occurs in the south, usually after 3–4 years, and in northern regions after 4–6 years.