Location: Food Quality Laboratory
Project Number: 8042-43000-015-00-D
Project Type: In-House Appropriated
Start Date: Jun 29, 2016
End Date: Jun 28, 2020
The overall goal of this project is to identify effective treatments that lead to improved product quality and nutritional value, and to identify the associated genetic elements responsible for fruit ripening and stress responses. Specific objectives are listed as follows: Objective 1: Evaluate and characterize changes in fruit ripening, postharvest nutritional and sensory quality parameters of strawberries due to pre- and post- harvest treatments with selected compounds, UV and calcium. Sub-objective 1.A. Identify effective treatment strategies that delay fruit ripening, improve postharvest nutritional and sensory quality parameters, and extend shelf-life. Sub-objective 1.B. Apply selected effective treatments to commercially harvested varieties of strawberries from different geographical regions, and validate efficacy and applicability of treatment(s) for industry. Objective 2: Identify key genes and signaling pathways regulating fruit ripening and biosynthesis of sugars, acids, volatile compounds and phenolics in response to effective treatments. Sub-objective 2.A. Conduct bioinformatic analyses of global gene expression profiles and correlate results with those obtained for physiological, metabolomic and sensory evaluations and identify candidate genes and signaling pathways that regulate the nutritional and sensory quality parameters. Sub-objective 2.B. Produce transgenic plants/fruits with the increased or reduced expression of selected candidate genes. Determine whether the up- and down- regulation of a single gene may mimic the improved quality traits that were observed in wild-type fruits following treatments.
Locally grown strawberry fruit will be subjected to pre- and postharvest treatments with selective compounds, ultraviolet irradiation and calcium. Selective compounds are synthesized organic compounds, for example, the derivatives of benzoate, which have shown effect on fruit ripening and color. Fruit quality traits including firmness, soluble solid content, total titrable acid content, color and decay, as well as sensory parameters, such as taste, flavor and appearance, will be evaluated. Treatments that enhance nutritional and sensory quality will be further tested on diverse strawberry varieties produced by commercial strawberry growers throughout the United States. The metabolome profiles of targeted fruit phenolics and volatile compounds correlated to nutrition and flavor/aroma in selected treatments will be analyzed by HPLC and GC-MS to determine which metabolites and pathways are altered. Global gene expression profiles in treated fruit will be analyzed by RNA sequence and bioinformatics analysis. The analyses will focus on genes involved in oxidative signaling, calcium signaling, and ABA signaling, as well as on the phenylpropanoid pathways and genes affecting biosynthesis of sugars, acids, volatile compounds. Stable or transient transformation with silencing or over-expression gene constructs driven by constitutive or fruit-specific promoters will be used to assess the function of specific genes in various aspects of fruit physiology and metabolism, including ripening, sensory parameters, responses to stresses, and accumulation and/or retention of health-beneficial secondary metabolites from the phenylpropanoid pathway. Quality traits including flavor, color, firmness, stress tolerance, and phytonutrient content will be analyzed in the transgenic lines.