2010 Annual Report
1a.Objectives (from AD-416)
The primary goal of this project is to enhance post-harvest flavor and nutritional quality and overall marketability of important fruit and vegetable crops. Over the next 5 years, research will be organized within the following two objectives:
Objective 1: Evaluate the effects of pre-harvest production and post-harvest processing and storage treatments on fruit flavor maintenance and/or enhancement in diverse accessions and breeding lines of Capsicum pepper, Malus serversii apple and blueberries; determine underlying molecular mechanisms controlling flavor quality.
• Sub-objective 1A. Evaluate fresh produce for chemical constituents, sensory attributes and underlying molecular mechanisms that contribute to fruit flavor quality in diverse accessions of Capsicum pepper, Malus serversii apple and rabbiteye blueberry.
• Sub-objective 1B. Determine the impact that selective plant breeding and post-harvest fresh-cut processing and storage have on fruit flavor maintenance and/or enhancement.
Objective 2: Evaluate the effects of pre-harvest production and post-harvest processing and storage treatments with potential to increase post-harvest concentrations of phytonutrients and antioxidant capacity in fruit of selected Capsicum species, Malus serversii apple and blueberries, focusing on pre-harvest foliar potassium fertilization, post-harvest heat and high-oxygen storage treatments.
• Sub-objective 2A. Evaluate the potential for pre-harvest foliar potassium fertilization, post-harvest treatment with heat and high oxygen storage to maintain or increase antioxidant capacity, antioxidant and/or other phytonutrient concentrations of fruit.
• Sub-objective 2B. Determine the effects of pre- and post-harvest treatment strategies that increase or aid retention of antioxidant capacity or phytonutrient concentrations on flavor quality of fruit from selected genotypes.
1b.Approach (from AD-416)
Fruit from about 250 non-cultivated and cultivated accessions of Capsicum peppers, 30 to 50 cold hardy rabbiteye blueberry cultivars and up to 200 accessions of non-cultivated accessions of Malus sieversii and (M. sieversii × M. ×domestica cv. Gala) F1 hybrids will be evaluated for flavor quality-related substances using established gas chromatography, liquid chromatography and sensory methods. Substances for flavor-related evaluations will include aromatic volatiles, free sugars, organic acids, capsaicinoids and their analogs (pepper only), phenolic acids, saponins and colored antioxidants (i.e., anthocyanidins, carotenoids). Measurements will be made on mature fruit that have been freshly harvested and following various storage periods. Fruit from accessions (pepper, apple, blueberry) identified as having high flavor (and associated nutritional) quality attributes will be further evaluated for sensory quality using consumer (untrained) panelists and for efficacy of pre- and post-harvest processing treatments to further enhance quality. Pre-harvest treatments will primarily focus on emerging foliar potassium fertilization protocols that enhance nutritional quality and post-harvest treatments will emphasize various short-term heat, light and high oxygen storage treatments.
Next, intraspecific crosses will be made between peppers with high flavor/nutritional quality and commercial bell pepper breeding lines. Resulting F1 families will be selfed to create F2 mapping populations and segregating F2 populations will be selfed to create F3 populations. Fruit from F3 plants will be phenotyped for flavor quality and parental lines and segregating F2 populations will be genotyped using SNP marker technology: quantitative trait loci for flavor quality will be identified. Intraspecific crosses will also be made between M. sieversii with unique flavors and a domesticated apple cultivar (Gala) and resulting F1 families evaluated for flavor quality and further backcrossed with ‘Gala’ to create uniquely flavored, high quality breeding lines.
Concurrent with flavor quality evaluations, flavorful fruit from non-treated apple, blueberry and pepper genotypes and those from pre-harvest foliar potassium fertilizations and post-harvest heat, light and high oxygen storage treatments will be evaluated for antioxidant activities (i.e., oxygen radical absorbance capacity, hydroxyl radical and superoxide radical scavenging capacity and DPPH activity), superoxide dismutase activity, vitamins (provitamin A, B9, C, E and K1) and other phytonutrients/minerals using established in-house procotols.
Fruit from select accessions/cultivars with increased post-harvest nutritional and/or analytical quality attributes will be evaluated by consumer panels for acceptability and intensity of sweetness, sourness, specific flavors depending on fruit type and texture and for acceptability of overall eating quality. Fruit from uniquely flavored, high nutrient pepper accessions will be further evaluated for the effects of fresh cutting on maintenance of flavor and nutritional quality and shelf stability.
Fruit of the worldwide cultivated green bell pepper (Capsicum annuum) often lack the unique flavor qualities of chili peppers. As a result, worldwide production of green bell peppers has stagnated while production of chili peppers has more than doubled over the past decade. While less cultivated than bell peppers, ají chili peppers (C. baccatum) are well known for their fruity flavor qualities. During the past year, we have selected fragrant, tasty C. baccatum accessions and have identified flavor-related aromatic volatiles, sugars, organic acids, and capsaicinoid-related antioxidants in fruit from those accessions. Many of these compounds are lacking or occur at significantly lower levels in green bell peppers. Since the start of this Project, we have optimized techniques to quantitatively measure the flavor-related compounds thus far identified as being important flavor-related substances in ají chili peppers. The on-going characterization of flavor and nutritional quality attributes in ají peppers is the first step towards development of improved C. baccatum cultivars with novel flavor and nutritional attributes and the introgression of those desirable attributes into bell pepper (C. annuum) breeding lines. Improving the flavor quality of green bell peppers will increase consumer consumption of this nutritional fruit.