Location: Food Quality Laboratory2011 Annual Report
1a. Objectives (from AD-416)
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. (Saftner and Lester). 2. Evaluate technologies to maintain the quality and marketability of fresh and fresh-cut produce through integrated microbiological and physiological approaches and innovations in post harvest handling, sanitation, and modified atmosphere packaging technology. (Luo and Bowker)
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.
3. Progress Report
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. We have selected fragrant, tasty C. baccatum varieties and have identified flavor-related aromatic volatiles, sugars, organic acids, and capsaicinoid-related antioxidants in fruit from those varieties. Generations of pepper families have been created and three third generation families have been screened for fruit flavor quality. Identifications of flavor-related gene sets are being made. This on-going characterization 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. Flat-leaf varieties of spinach have higher levels of vitamins A, B9, E, and K and carotenoids. Higher vitamin and carotenoid levels were also found in younger leaves, plants grown in clay soils, and plantings established under long day-lengths. This means that enhancement of spinach nutritional quality and marketability can be achieved at the grower level through cultivar selection, site selection, planting date, and targeting harvesting around leaf age. New varieties of fruits and vegetables are needed to combat plant diseases and to enhance produce quality and shelf stability. Scientists from Beltsville, MD, worked closely with geneticists from Salinas, CA, in developing new Verticillium wilt-resistant lettuce varieties and evaluating their quality and storage life, especially after cross-country shipment. This collaborative research has led to the development and release of two new disease resistant lettuce varieties with improved quality and shelf stability. Additional breeding lines are currently being evaluated for improved shelf stability for packaged fresh-cut products and disease resistance. Assay parameters for optimizing melon fruit phospholipase D (PLD) activity were developed. PLD activity is a regulator of fruit softening and was found to be controlled by pH, cofactor calcium and substrate levels, reaction time and temperature. An in-depth evaluation of rapid versus slow softening melon cultivars is confirming the optimal assay parameters prior to down-regulating PLD activity in genetically modified melon flesh.