Blush Seedless
| Variety Passport | |
| Country of origin: | USA |
| Breeder: | Harold Olmo, University of California, Davis |
| Variety number VIVC: | 1472 |
| Prime name: | Blush Seedless |
| Breeding number: | 31-37F |
| Commercial name: | Blush Seedless |
| Patent: | PP4856 (USA) |
| Principal Synonyms: | 31-37F, Davis 31-37 F, Ashlamish Amar |
| Year of obtaining / registration: | Cross made in May 1966, patent filed on September 22, 1980, and granted on June 8, 1982. |
| Pedigree given by breeder: | Emperor × California Selection Z4-87 |
| Pedigree confirmed by markers: | Emperor × California Selection Z4-87 |
| Species: | Vitis vinifera |
| Ripening period: | Late |
| Classification and Use: | Table, Seedless, Commercial sale, Long-term storage |
| Resistance group: | Susceptible |
| Data Sources: | Vitis International Variety Catalogue (VIVC), Google Patents |
| Agrobiology | |
| Vigor: | vigorous |
| Flower type: | hermaphrodite |
| Winter hardiness: | Non-hardy (-15...-17°C) |
| USDA Hardiness Zone: | Zone 7 (down to -17.8°C) |
| Pruning length: | short, 2-4 buds |
| Clusters and berries | |
| Bunch shape: | conical |
| Bunch density: | medium, dense |
| Average bunch weight: | 450 g |
| Berry shape: | ovoid |
| Berry skin color: | red |
| Average berry weight: | 3,8 g |
| Seed development: | rudimentary seeds |
| Flesh texture: | fleshy |
| Berry skin thickness: | Thin |
| Berry skin texture: | tender |
| Sugar content: | 16-18% |
| Total acidity: | 4-5 g/l |
| Flavor type: | Neutral |
| Ampelographic overview |
Main Characteristics
Blush Seedless (identified in patent documentation as selection form 31-37F) is a table grape variety of American origin featuring seedless characteristics. It was bred by geneticist Harold P. Olmo in May 1966 at the University Vineyard at Davis (California, USA) by crossing the Emperor variety with the California selection Z4-87. Plant Patent number PP4856 was officially granted on June 8, 1982. The grape variety belongs to the Vitis vinifera species. The initial asexual reproduction by Yema budding (grafting) onto Ganzin 1 rootstock was carried out on September 9, 1970, at the Kearney Horticultural Field Station.
The ripening period of the grapes is late, though it achieves coloring and maturity earlier than the parental Emperor variety. The first coloring (veraison) under California conditions is recorded in late July (approximately July 25), and the fruit becomes fully colored by August 20. The grape variety is characterized by a stable, heavy crop. The primary cluster averages 450 grams in weight and bears an average of 250 berries. The average weight of a berry (calculated from the 10 largest per cluster) is 3.8 grams. The commercial harvest exhibits excellent shipping and cold storage qualities similar to Emperor.
Morphological Description of the Blush Seedless Grape Variety
Official morphological and ampelographical characteristics are recorded in the patent specification based on seasonal observations at experimental stations:
- Growth habit: the vines are vigorous, with a growth habit similar to Emperor, but producing more numerous and slenderer cured canes. The trunk is straight with loose and abundant bark. Bud burst is late, occurring with or slightly before Emperor. First blossoms are recorded around May 17. The vine is adapted to short spur pruning on a bilateral cordon.
- Young shoot tip (12"–14" long): straight and very slender. The youngest leaves are white woolly above and below, with teeth edged carmine. The half-expanded leaf features loose, scattered hairs (not flocculent), and the blade is very undulated with lobes folded inward. Petioles and shoots develop a distinct maroon coloration on sun-exposed portions; the surface is ribbed. The inflorescence is very narrow and linear.
- Shoot: strongly attached to the cane, flattened especially at the nodes, and marked with maroon striations. Leaf fall occurs late in the season. Under a heavy crop load, the foliage displays visual symptoms of magnesium deficiency.
- Formed leaf: large-sized (blade dimensions are 18.5 × 19.6 cm) and almost entire. The under surface is covered with floccose woolly hairs. Superior lateral sinuses are reduced to shallow slits, overlapping and completely closed. The teeth are large and acute, featuring very straight sides. The petiolar sinus is deep, open, and lyre-shaped. The petiole is slender, with a length of 9.5 cm.
- Cluster structure: the primary clusters are large, well-filled to compact, measuring approximately 12 × 36 cm. The geometric shape is uniformly long conical and symmetrical. The main rachis (stem) is 6 mm in diameter, woody and brown. Clusters are usually borne freely pendant at the fourth node, or less frequently at both the fourth and fifth nodes. A few small, persistent green immature shot berries are sometimes present at the apical end of the cluster.
- Berry characteristics: the berries have an ovoid shape. The skin is tender, and the flesh is meaty and firm. At full maturity, the fruit turns a deep, bright pink or red color without a purplish cast. The Blush Seedless grape variety is essentially seedless; the seeds develop only partly, remaining green, fleshy, and soft, making them imperceptible during fresh consumption. The pedicels are slender and warty, 9–10 mm long, with a small torus.
Viticultural Features
The Blush Seedless variety demonstrates high fruitfulness, with basal buds being significantly more fertile than those of Emperor. To optimize the light environment and achieve better fruit coloring, leaf removal in the cluster zone and careful cane positioning are highly recommended. The fruit can be retained in good condition on the vine for a long period after reaching maturity. This new variety succeeds best in sites where the Emperor variety has historically been successful. Morphologically, it most resembles the Ruby Seedless variety but is later maturing and possesses a brighter red berry color.