Eco-Physiological Parameters and Agronomic Traits of Pomegranate Cultivars From the USDA National Clonal Germplasm Repository
- Author(s): Chater, John Matthew
- Advisor(s): Merhaut, Donald J
- et al.
Pomegranate (Punica granatum L.) is an ancient deciduous fruit tree crop in the family Lythraceae. Pomegranate juice is a highly valued beverage, long believed by many of the world’s cultures to possess medicinal properties. Recently the juice has been demonstrated to contain large quantities of polyphenolic compounds with powerful antioxidant properties. Commercial pomegranate planting area has increased substantially in the western hemisphere due to increased consumer interest. Low nursery inventory has caused many farmers to propagate their own trees and limited availability of only a few cultivars is believed to have contributed to the lack of diversity in the market. ‘Wonderful,’ the industry standard, has been propagated in the U.S. for decades and dominates the market, leading to the present-day monoculture. The USDA-ARS pomegranate germplasm collection conserves approximately 280 cultivars, many of which have not been evaluated for commercial production. In this dissertation, 14 preselected pomegranate cultivars from the USDA collection were evaluated: 1) to develop protocols that optimize propagation of pomegranate for nurseries and growers; 2) in new field trials planted specifically to determine establishment rates, productivity and eco-physiological performance of different cultivars in inland versus coastal environments; and 3) to establish dates of fruit maturity, identify unique cultivars with consumer-friendly traits, and to select candidates that meet or exceed juice quality parameters of Wonderful. The overall goal of this research was to identify promising pomegranate cultivars with the potential to be developed for commercial production in coastal and inland areas of southern and central California. Propagation experiments determined that some pomegranate cultivars were difficult to root. Establishment rates and precocity were significantly different among cultivars and between sites, with the inland planting producing more fruit than the coastal site. Juice quality for 14 cultivars was chemically analyzed with spectrophotometry, refractometry, titration, nuclear magnetic resonance, ion and liquid chromatography to identify candidate cultivars meeting or exceeding Wonderful juice quality specifications. This research was the first of its kind to establish experimental field trials of pomegranate germplasm in California to quantify and provide phenotypic, eco-physiological and horticultural data for growers, breeders, and the food and beverage industries.