Blanc Seedless

Main Characteristics

Blanc Seedless is a new table grapevine variety artificially created by American researcher Joseph Maranto within a selection program initiated in 1992 in a vineyard located near Delano (San Joaquin Valley, California). The variety was obtained from a crossbreeding of the red-fruited parental varieties Red Globe as the female parent and Crimson as the male parent. The Blanc Seedless grapevine variety is characterized by a late ripening period. Under the ecological conditions of Central California, commercial cluster maturity occurs in mid-October, which is approximately four weeks later than the harvest period of the standard Thompson Seedless variety.

The hybrid under consideration demonstrates high productivity potential when managed with short spur pruning. The crop yield is represented by conical shouldered clusters ranging from loose to compact in structure, with an average weight of approximately one pound (about 450 grams). The light green berries have an average weight ranging from 6 to 8 grams, featuring a thick, firm skin and a crisp, firm flesh with a mild sweet flavor. At the time of harvest, the soluble solids accumulate to an average of 19.0% sugar, with a titratable acidity level of 4.64 g/l and a juice pH of 3.85. The Blanc Seedless grapevine variety is primarily oriented toward dessert use, showing a distinct resistance to adverse weather conditions and an apparent superior shelf life.

Morphological Description of the Blanc Seedless Grapevine Variety

• Vine and Cane: The mature vine is large, appearing as a bush, and exhibits a vigorous growth habit. The trunk is slender and covered with dark brown bark including long split strips; the underbark color is identified as India tan. The mature dormant canes feature a medium length and width, with 16 to 20 nodes per cane, displaying a raw sienna coloration. The nodes are round and slightly enlarged, with internode lengths varying from 76.2 to 127.0 mm. The shoots are smooth, medium to long, and circular to slightly flat in cross-section. The variety shows a characteristic tendency to produce a small secondary (lateral) crop on the current season's growth.
• Tendrils: Developed along the shoots in sparse numbers and arranged discontinuously. The tendril texture is smooth, featuring a bifurcated or trifurcated form with an average length ranging from 101.6 to 203.2 mm.
• Buds: The buds exhibit a medium size and a slightly pointed configuration. In the specified location of the San Joaquin Valley, bud break commonly occurs at the end of March. The basal buds of the shoot are mostly fruitful.
• Leaves: The leaves are generally medium to large in size (with an average mature leaf length ranging from 101.6 to 152.4 mm) and feature a heavy density on the vine. The leaf blade is four-pointed. The upper surface is smooth and dark green (cossack green), while the lower surface is light green and completely glabrous (lacking pubescence). The petiole sinus is U-shaped, with the lateral sinuses occasionally overlapping. The midrib and leaf veins display a grape green coloration. The leaf margins are serrate with irregular pointed teeth, numbering 10 to 14 per lobe and totaling 50 to 60 teeth across the entire blade. The petiole is round or flattened, measuring from 76.2 to 127.0 mm in length.
• Flowers: The bloom date begins on May 5, with the full bloom stage reached between May 10 and May 12. A visible berry set is recorded by May 18. The inflorescence size is medium, bearing an average of two per spur and totaling 30 to 35 inflorescences per vine based on a 16-spur pruning system. The flowers are fertile, featuring upright stamens with abundant pollen and light green (calla green) pistils.
• Cluster and Berry: The clusters are uniform, exhibiting a conical shouldered configuration with a compactness ranging from loose to compact. The berries are mostly uniform, ellipsoidal elongated in shape, with a longitudinal axis dimension of 20 to 25 mm and a transverse diameter axis of 14 to 16 mm. The berry count ranges from 100 to 140 per cluster. The skin is thick and firm, displaying a light green skin coloration; exposed berries develop an amber yellow sunburn. A single small, round, pore-like lenticel is visible on the distal end of the fruit. The internal pulp is light green, adheres to the skin, features a crisp texture, and is completely seedless with a colorless juice.

Viticultural Characteristics and Orchard Management

The Blanc Seedless grapevine variety is distinguished by a large vine size and high productive capacity when short spur pruning is applied. For asexual reproduction, the variety was successfully grafted onto mature Thompson Seedless grapevine rootstock in 1998, and the stability of its typical characteristics was confirmed in subsequent generations. The berry skin is firm and shows no tendency to crack or split under standard management practices. The attachment of the berry to the pedicel is strong, supported by a durable capstem structure.

The grapevine variety under description shows a high resistance to adverse environmental stress conditions, including cold, drought, extreme summer heat, and wind. The specific resistance profiles to fungal or bacterial diseases are noted as unknown within the initial sortexperimentation records. While the shipping and handling qualities were left untested during early field observations, the firm texture of the fruit renders it well-suited against mechanical damage. The Blanc Seedless grapevine variety demonstrates an excellent keeping quality; after two months in commercial storage facilities, the clusters still remain in good appearance and retain their commercial value.

* VINEYARD Note: The image published herein has been reconstructed from a printed version and may therefore contain inaccuracies in color reproduction.