Date of Graduation

5-2014

Document Type

Thesis

Degree Name

Master of Science in Horticulture (MS)

Degree Level

Graduate

Department

Horticulture

Advisor/Mentor

John R. Clark

Committee Member

Renee T. Threlfall

Second Committee Member

M. Elana Garcia

Third Committee Member

Luke R. Howard

Keywords

Fungicide, Muscadine, Nutraceuticals, Postharvest, Storage

Abstract

A major limiting factor in muscadine grape (Vitis rotundifolia Michx.) commercialization is deterioration during storage. One solution for extending market seasons and preventing market saturation for fresh muscadines could be the release of new cultivars with improved postharvest storability. Three studies were conducted; Study 1: The effect of fungicide treatments on muscadine genotype postharvest storage and nutraceutical content; Study 2: An evaluation of a diverse range of genotypes for postharvest storage potential and nutraceutical concentrations; and Study 3: The impact of postharvest storage and berry segment on the nutraceutical composition of `Supreme'. Research on table grapes has shown that field fungicide applications increase storability, but little is known of their effect on muscadines. The effect of field applications of fungicides on composition attributes during postharvest storage was evaluated on five muscadine cultivars (Nesbitt, Southern Jewel, Summit, Supreme, and Tara) and five breeding selections from the University of Arkansas Fruit Breeding Program. There were two field treatments (no fungicide and fungicide). For the fungicide treatment, alternating applications of two fungicides were applied at 14 d intervals during berry development. Fruit was harvested and composition attributes including berry volume, titratable acidity (TA), pH, soluble solids (%), soluble solids to titratable acidity ratio (SS/TA), color (L*, Chroma, and hue), firmness (force to penetrate berry skins), weight loss (%), and unmarketable fruit (%) were evaluated every 7 d for three weeks. An additional eight cultivars and selections from non-fungicide-treated vines were subjected to postharvest storage potential evaluations. These included AM 02, AM 03, AM 18, AM 26, AM 28, `Delicious', `Fry', and `Ison', as well as the genotypes from the non-fungicide-sprayed vines of genotypes in Study 1 (AM 01, AM 04, AM 15, AM 27, `Nesbitt', `Southern Jewel', `Summit', `Supreme', and `Tara') to broaden the evaluation and comparison among genotypes for postharvest storage potential, and aid in the development of an Arkansas muscadine storage protocol. Additionally, a third study was conducted with `Supreme' to determine the retention of nutraceutical compounds during storage on the berry segments of flesh (pulp and skin), seeds, and whole berries and to evaluate the variability in nutraceutical compounds among different vine of a single genotype. The storage attributes of force to penetrate the berry skin, percent weight loss, and percent unmarketable were all improved with fungicide applications, while the difference in percent volume change was minimal. Field fungicide applications had no effect on muscadine berry color (Chroma, hue angle, and L*) or berry composition (pH, TA, SS/TA, and soluble solids). There were some effects of field fungicide applications impacted some nutraceutical levels, however results varied. Weight loss, percent unmarketable, and force have potential for routine measurements in postharvest evaluation of muscadines, while percent volume change was found to be less useful. Titratable acidity, pH, soluble solids, and SS/TA can be useful measurement for ripeness, but not for storability. Chroma and hue angle are not indicators of storability, while L* shows potential, and nutraceuticals largely do not change during storage. The genotypes AM 04, AM 26, AM 27, AM 28, `Southern Jewel', and `Supreme' were identified as having the highest storage potential, while AM 01, AM 15, AM 18, and `Tara' had the least storage potential. The genotypes AM 03, AM 04, AM 27, and `Ison' were identified as having the highest overall nutraceutical content, while AM 18, AM 28, `Supreme', and `Tara' had the lowest overall nutraceutical content. Furthermore, muscadine grape nutraceuticals and antioxidant capacity vary by berry segment and vine. The primary contributors as sources of variation were found to be genotype, year, and storage time.

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