Location: Physiology and Pathology of Tree Fruits Research
Project Number: 2094-43000-008-040-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Jan 1, 2023
End Date: Dec 31, 2024
Objective:
The 2023 Washington Tree Fruit Research Commission (WTFRC) and Oregon Sweet Cherry Commission (OSCC) research priority list includes “determining sweet cherry cultivar-specific export suitability”.
Large fruit size, firmness (>300 g/mm), dark fruit color (dark red to mahogany, uniform), green stem (potentially differing interests in short versus long stem length), and defect-free (decay, pitting, and cracking) are the key characteristics for fruit destined for export (industry communication).
Challenges in delivering high-quality sweet cherries to export markets may include long transport duration, temperature fluctuations and extremes, vibration and drop forces, and either insufficiently modified atmospheres (MA) at above-optimal storage temperature, leading to higher than optimal respiration and more rapid loss of quality) or anaerobic conditions resulting from modified atmosphere packaging (MAP), leading to off-flavors. Cultivars whose fruit have greater tolerance to these potential transport stressors may be better suited for export.
Remaining knowledge gaps applying to sweet cherry cultivar export suitability include:
1) Transport timelines detailing temperature extremes, vibrational and drop forces occurring in transport, which are important for evaluating cultivar resilience to these factors in a laboratory setting,
2) Fruit quality at harvest relative to post-transport for both presently exported as well as newer or potential cultivars, especially changes occurring in firmness, stem color, soluble solids, acidity, pitting, and postharvest decay.
3) An evaluation of the interaction between sweet cherry cultivars and actual transport stresses.
Approach:
In Year 1 (2023 growing season), we will collect data regarding Transport Stresses and perform a Cultivar Comparison. In Year 2 (2024 growing season), we will repeat the Cultivar Comparison from Year 1, and add treatment(s) as warranted based on transport stresses from year 1 for an evaluation of the Influence of Transport Stress on Cultivar Quality.
1. Transport stresses. Dataloggers collecting temperature, humidity, and vibration/drop will be placed shipments of fruit departing from the Pacific Northwest to overseas destinations. The number of devices and breadth of data will be determined by datalogger expense and packinghouse participation. To encourage participation, participating sales desks/packinghouse information will remain anonymous.
2. Cultivar comparison. We will evaluate cultivar suitability for export in a two-factor experiment. Experimental factors will be cultivar and storage atmosphere (air or modified atmosphere packaging [LifeSpan]). For this experiment, we will maintain the optimal storage temperature of 32 °F for the duration of the experiment.
The experimental unit will be 1 lb bags (~100 fruit) (either perforated plastic or LifeSpan MAP bags) of sweet cherries, with three replications per location. Program personnel will harvest fruit from up to three locations for each cultivar, according to logistics constraints (e.g. personnel availability, relative harvest timing, location availability). Orchard location will be both a pre-harvest and postharvest blocking factor in statistical analyses as all bags of fruit from an orchard will be stored in a box together. We will evaluate respiration weekly (with a handheld device for CO2 and O2) and fruit quality at harvest and at 6 weeks of storage for each bag:
Whole bag:
1. Initial weight, final weight (weight loss).
2. Pitting counts according to these categories: none, present but not market limiting, market limiting.
3. Pebbling counts according to the categories: none, present but not market limiting, market limiting.
4. Decay counts (visually present/absent).
5. Stem (present/absent).
6. Stem color (fully green, less than 15% brown/not market limiting, greater than 15% brown/market limiting).
7. Stem desiccation (not desiccated/desiccated).
8. Cracking counts according to these categories: none, present but not market limiting, market limiting.
10 random fruit per bag:
9. CTIFL color (skin).
10. Colorimeter (lightness, hue, chroma).
11. Glossmeter.
12. Firmness (g/mm).
13. Stem pull (g).
14. Fruit diameter (mm).
15. Bulk soluble solids (all 10 fruit juiced together) (degrees Brix).
16. Bulk titratable acidity and pH (all 10 fruit juiced together) (% malic acid equivalents)
Additionally, 5 fruit per bag will be pitted and frozen for additional laboratory analyses, potentially including volatiles.
Potential cultivars include Benton, Black Pearl, Bing, Coral Champagne, Cowiche, Cristalina, Lapin, Regina, Riker RR2, Skeena, Staccato, Suite Note, and Tamara.
