Recipient Organization
UNIV OF WISCONSIN
21 N PARK ST STE 6401
MADISON,WI 53715-1218
Performing Department
Horticulture
Non Technical Summary
In the last decade, the cranberry market has experienced a rapid shift from mostly juice production to higher value products such as thesweetened dried cranberry (SDC). SDCs require higher fruit quality parameters than juice production, in particular higher fruit firmness. Growers in Wisconsin and across North America struggle to produce the premium priced firm fruit required for SDC production, resulting in overproduction of lower value juice concentrate, thus reducing growers' profitability.The goal of this project is to investigate changes in cranberry fruit firmness during the ripening period by evaluating physiological and anatomical changes in the fruit, as well as preharvest factors that affect fruit softening. The objectives of this study are: 1)investigate key aspects of fruit ripening in cranberry, including fruit quality,cell wall composition, cell wall modifying enzyme activities, and cuticle thickness to obtain fundamental information needed to determine best timing for harvest to increase efficiency of SDC production; 2)investigate the relationship between fruit stomatal functioning and calcium accumulation during different stages of fruit development to develop feasible practices for increasing calcium levels in the fruit and hence fruit firmness; 3) evaluate if calcium fertilization can increase calcium content in cranberry fruit and firmness.The information generated by this project will help growers make better informed decision on 1) timing of fruit harvest based on optimal fruit firmness and 2) production practices that can reduce preharvest fruit softening, to increase production of high-quality fruit and increased efficiency of SDC production, therefore increasing grower revenue.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
0%
Goals / Objectives
The goal of this project is to investigate changes in cranberry fruit firmness during the ripening period by evaluating physiological and anatomical changes in the fruit, as well as preharvest factors that affect fruit softening. The objectives of this study are:Objective 1:Investigate key aspects of fruit ripening in cranberry, including fruit quality,cell wall composition, cell wall modifying enzyme activities, and cuticle thickness to obtain fundamental information needed to determine best timing for harvest to increase efficiency of SDC production.Objective 2:Investigate the relationship between the distribution and function of fruit stomata and Ca accumulation during different stages of fruit development in cranberry to obtain necessary information to develop feasible practices for increasing Ca levels in the fruit.Objective 3:Evaluate if Ca fertilization can increase Ca content in cranberry fruit and firmness. Two methods of application will be compared: foliar applications from early bloom to early fruit development stages and soil application postharvest to increase plant Ca reserves.
Project Methods
Objective 1.For this objective, two cultivars will be evaluated, the industry standard 'Stevens', categorized as a firm fruit cultivar, and 'BG', categorized as a soft fruit cultivar. Fruit will be harvested from mature beds from the same farm at four ripening stages: pale green, blush, red, and dark red stages. Fruit quality will be determined by evaluating fruit weight, firmness, and total anthocyanins.Fruits will be weighed using a digital balance. Fruit firmness will be evaluated as the maximum compression force (MCP) needed to compress each berry tested by 20% of its volume, using a 1 mm·s-1test speed in a Texture Analyzer (TA.XTPlus Connect, Textural Technologies, Hamilton, MA, USA). Total anthocyanins (TAcy) will be determined using 0.1 kg of whole berries homogenized in 100 ml of extracting solution (95% ethanol/1.5 N HCl, 85:15, v/v), using a high-speed blender. After overnight diffusion into the solution, anthocyanins samples will be centrifuged, and the supernatant absorbance will be measured at 535 nmwith aGenesys 5 UV-vis spectrophotometer (Thermo Electron Corp., Milton Roy, NY, USA)and expressed as mg total anthocyanins kg-1.Isolation, fractionation, and quantification of cell wall materials: Cell wall materials will be isolated in the form of alcohol-insoluble residue(Figueroa et al., 2012). Two independent extractions will be performed at each stage. Isolated cell wall materials will be fractionated into water-soluble pectins, EDTA-soluble pectins, HCl-soluble pectins, NaOH-soluble polymers (hemicelluloses), and H2SO4-soluble polymers (celluloses)(Figueroa et al., 2010). Pectin contents will be estimated by measuring uronic acid contents in each pectin fraction using the m-hydroxydiphenyl methodwith galacturonic acid as a standard and expressed as μg galacturonic acid mg-1alcohol-insoluble residue. Hemicellulose andcellulose contents will be estimated using the anthrone methodwith glucose as a standard and expressed as μg glucose mg−1alcohol-insoluble residue. The concentrations of galacturonic acid and glucose will be measured using a spectrophotometer (UV-visGenesys 5,Thermo Electron Corp.).Assays of cell wall modifying enzymes:Four independent extractions will be performed at each ripening stage. Polygalacturonase, α-arabinofuranosidase, β galactosidase, and β-xylosidase will be extracted and assayed as described by Figueroa et al., 2012, whereas α-mannosidase and endo-1,4-β xylanase will be assayed according to the methods of Chen et al.(Chen et al., 2015)and Manenoi and Paull(Manenoi and Paull, 2007), respectively. Enzyme activities will be determined using a spectrophotometer (UV-visGenesys 5,Thermo Electron Corp.).Cuticle thickness and interaction with epidermal cells:The equatorial portion of the fruit will be selected for measuring cuticle thickness. Cross-sections perpendicular to the fruit surface, 100 µm thick, will be made with an Oxford Vibratom (Model G, Oxford Co., San Mateo, CA), as this instrument allows thin-sectioning of plant tissue without fixation. The cuticle thickness of the thin-sections will be measured with the use of a light microscope Olympus BX60 (Olympus Optical Company, Tokyo, Japan) connected to a Canon digital camera (EOS Rebel T6i, Tokyo, Japan).Objective 2.This objective will investigate the relationship between fruit stomatal functioning and Ca accumulation during different stages of fruit development in cranberry. Stomatal conductance of the berries will be measured on sunny days using a steady-state porometer (model LI-1600; LI-COR, Lincoln, NE). Berries in the first two positions on the upright will be measured from petal fall to 50% blush. Stomatal density and distribution will be evaluated by counting the number of stomata on the berries. From petal fall to 50% blush, berries in the first two positions on the upright will be collected, and subsequently each berry will be divided into the calyx and four equal spherical segments: the distal (calyx) end, distal-middle end, proximal middle end, and proximal (pedicel).Each section will be coated with clear lacquer (nail polish), and after drying, the lacquer will be carefully peeled from the berries and placed on glass slides.Using a light microscope (Olympus BX60, Olympus Optical Company, Tokyo, Japan), the stomata will be counted for each section. Stomata on the berries will also examined under a scanning electron microscope (SEM) (FEI Quanta 200) available at the Newcomb Imaging Center at UW-Madison. Fruit will be sampledat four ripening stages: pale green, blush, red, and dark red stages. The skin (epidermis) will be carefully removed from the equator of each berry using a razor blade and prepared for fixation and mounting for SEM.Calcium content and berry dry weight will be evaluated by sampling berriesat the four ripening stages. Berries will be dried to constant weight in a drying at 60 °C and weighed using a digital balance. Dried samples will beground before being sent to AgSource, Laboratories (Bonduel, WI location) for percent calcium content analysis by nitric acid digestion.Objective 3. The third objective will be to test if cranberry fruit calcium content can be enhanced through fertilization. To do this, we will perform calcium fertilization trials using calcium chloride (CaCl2) and calcium sulfate (gypsum, CaSO4). Foliar applications will be made early in the growing season, from early bloom to early fruit development, as this is when any stomata present on the fruit will be most likely to be open and not occluded by waxes. Separate soil applications will be made in the fall (postharvest), a known period of increased root growth. Plots will be established in production beds of the cultivar 'Stevens' at the Wisconsin Cranberry Research Station near Millston, WI. Foliar CaCl2will be applied three times at rates equivalent to 400, 800, and 1200 g Ca ha−1over the period from early (10%) bloom, full bloom, and early fruit expansion. Single applications of CaSO4will be applied at three rates to the soil independently in late August (preharvest) and September (postharvest) for fruit quality evaluation the following season. Berry and leaf samples will be collected prior to commercial harvest for calcium content analysis and firmness testing. Sampled fruit and leaves will be dried and ground before being sent to AgSource Laboratories (Bonduel, WI location) for percent calcium content analysis by nitric acid digestion. Fruit firmness (maximum compression force and maximum compression distance) will be measured using a Texture Analyzer (TA.XTPlus Connect, Textural Technologies, Hamilton, MA). Soil samples will be taken prior to the start of treatment applications and at harvest and sent to AgSource Laboratories for pH (1:1 soil/water slurry) and Ca content (ammonium acetate extraction) analysis.