Joseph Maranto

Brief Biography and Chronology of Scientific Activities

Joseph Maranto is an American scientist, research agronomist, and breeder who made a fundamental contribution to the development of commercial fruit production, nut cultivation, and viticulture in the southern part of California's Central Valley. From the mid-1970s, he held the official position of Farm Advisor in the structure of the UC Cooperative Extension (University of California Agriculture and Natural Resources) for Kern County (Bakersfield), conducting active research activities at the university's Agricultural Extension Station.

The initial stage of his scientific recognition is associated with the development of the American pistachio industry. In 1989–1990, Joseph Maranto, together with Dr. Dan Parfitt from the University of California, Davis (UC Davis), co-authored and initiated a large-scale intervarietal hybridization program for pistachios. The result of these multi-year cultivar trials was the breeding and introduction into commercial production of the Golden Hills, Lost Hills, and Randy varieties, which fundamentally changed the structure of American nut production, providing earlier harvesting dates and a high percentage of split nuts. In the 1990s, the researcher applied his accumulated breeding experience to the field of viticulture.

Selection Work and the Creation of New Grapevine Varieties

Joseph Maranto's grapevine breeding program was built on the principles of a private-corporate partnership that combined university scientific methodology and the resources of a large agribusiness conglomerate. Experimental works were initiated in 1992 on the basis of the vineyards owned by Anton Caratan & Son, a prominent family agriculture company, located near the city of Delano (San Joaquin Valley, California). In these studies, Maranto acted as the creator of the varieties (Inventor), while the company took on the financing and subsequent patent ownership (Assignee).

The main scientific and practical task of the breeder was to develop large-fruited, completely seedless table grape varieties with late and ultra-late ripening periods to expand the region's export potential. The fruit had to withstand long-distance transportation by sea and land without losing its commercial qualities. To achieve these goals, the researcher gained access to advanced proprietary breeding genetics from the United States Department of Agriculture (USDA), actively involving the licensed variety Crimson Seedless as the male parent in crosses. The result of this work was the creation and registration of four commercially successful table grapevine cultivars:

• Mara Seedless: A pink-berried, mid-to-late season variety (patent US PP19,599 P2), obtained from the hybrid combination Red Globe × Crimson.
• Roma Seedless: A late-ripening, pink-berried variety (patent US PP21,075 P2), characterized by a firm meaty texture of the flesh and high post-harvest storage potential.
• Blanc Seedless: A late seedless variety with a light green skin coloration (patent application publication US 2005/0022277 P1), ripening a month later than the standard Thompson Seedless.
• Cara Seedless: A black-berried table variety featuring a dark eggplant skin coloration and a pronounced waxy bloom (patent application publication US 2008/0209603 P1).

Contribution to Viticultural Practices and Crop Load Management

In addition to direct hybridization, Joseph Maranto developed effective protocols for vegetative propagation and accelerated cultivar testing of grapevines. In 1998, he successfully tested a method for mass top-working (grafting) new grapevine selections onto established, mature Thompson Seedless vines, which allowed for a quick evaluation of the stability of ampelographic characteristics in subsequent vegetative generations under asexual propagation.

The researcher scientifically justified the methods of hormonal regulation and cluster thinning for the new seedless grapevine varieties. To prevent excessive cluster compactness, he introduced and patented a precise schedule for treating inflorescences with gibberellic acid solutions at the 80–90% bloom stage, followed by a repeat spray two weeks later. This viticultural practice eliminated the need for time-consuming mechanical trunk girdling to increase the linear dimensions and weight of the berries, thereby optimizing labor costs in commercial-type vineyards.