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Minimal dormant pruning after the first and second growing seasons, followed by standard pruning thereafter, improved total tree yield in the 3rd, 4th, and 5th years after planting. Trees that were pruned in accordance with standard local practice had ≈50% yield compared to minimally pruned trees in years 3 through 5. Fruit from minimally pruned trees was sgnificantly smaller, but mathematical adjustment of crop load indicated that overall yield efficiency was improved in the 3rd and 4th years for trees receiving minimal pruning.
Girdling has been shown to increase fruit size and soluble solids concentration and advance fruit maturity. Performed improperly, girdling can also have a debilitating effect on trees. To minimize this, growers often use alternatives to the standard complete girdle. However, the efficacy of these alternative techniques has not been evaluated. Three methods of girdling: 1) complete girdle of all scaffolds, 2) complete girdle of all but one “nurse” scaffold, and 3) spiral (overlapping) girdle of all scaffolds, were compared to ungirdled trees to determine their effect on fruit and tree performance. All of the girdling treatments increased fruit size and marketable yield, and advanced maturity over ungirdled trees. Fruit on ungirdled nurse limbs were similar in size to fruit on ungirdled trees, while the fruit on the remaining girdled limbs were slightly larger than fruit on the trees which had all scaffolds girdled. Overall fruit size and yield of trees with a nurse limb were similar to the other girdle treatments.
Previous research with Mayfire nectarine demonstrated that seed length can be used as a developmental marker to predict the optimum date of girdling. Four years of study indicates that seed length also appears to be an effective physiologic marker for integrating early season heat accumulation. Seed length development was more highly correlated with heat accumulation (r=0.936) than with number of days after bloom (r=0.699). However, harvest date is more accurately predicted by number of days between 12mm seed length and harvest (30±1) than by degree-days between 12mm seed length and harvest (337±21).
Respiration rate and bruising incidence were assessed in new cherry (Prunus avium L.) cultivars adapted to high temperatures. `Bing', `Brooks', `Tulare', and `King' respiration rates were evaluated at 0,5,10, and 20C, and bruising susceptibilities at 0, 10, 20, and 30C. `Bing' was the least susceptible to bruising and had the lowest respiration rate at all temperatures. Respiration rate increased with temperature in all cultivars. Impact bruising damage was greatest in all cultivars when fruit flesh was below 10C. Vibration damage was not influenced by fruit temperature. Our results suggest that the cherry cultivars assessed should be handled at temperatures between 10 and 20C during packing to minimize bruising damage. Due to increased respiration rates at higher temperatures, however, fruit should be cooled to 0C within 4 to 6 hours after harvest.
Skin discoloration (SD) formation in peach [Prunus persica (L.) Batsch] and nectarine [Prunus persica (L.) Batsch, var. nectarine] was related to physical damage (abrasion) to the fruit during fruit handling (harvest and hauling operations) within the orchard and during transport to the packinghouse. Vibration and rubbing treatments increased SD formation indicating that tissue damage is involved in SD formation. Anatomical studies comparing sound and SD-injured tissues done by scanning electron and light microscopy indicated that very-low-intensity physical damage could induce brown and/or black spots because of cell disruption in the epidermal and hypodermal layers. The fact that injury was specific to the exocarp tissues (cuticle, epidermis, and hypodermis), and that mesocarp tissue located below the exocarp cells remained sound and turgid, indicated that abrasion injury is associated with SD. Similar types of visible and anatomical injury characteristics were induced by a rubbing treatment, demonstrating that physical abrasion damage affecting just exocarp cells was enough to induce SD:
The influence of modified atmosphere packaging (MAP) on quality attributes and shelf life performance of ‘Friar’ plums (Prunus salicina) was studied. Plums were stored at 0 °C and 85% relative humidity for a 60-day period in five different box liners (LifeSpan L316, FF-602, FF-504, 2.0% vented area perforated, and Hefty liner) and untreated (control). Flesh firmness, soluble solids concentration, titratable acidity, and pH were unaffected by the box liners. Fruit skin color changes were repressed on plums packed in box liners that modified gas levels and weight loss was reduced by the use of any of the box liners. Plums packed without box liners (bulk-packed) had ≈6% weight loss. High carbon dioxide (CO2) and low oxygen (O2) levels were measured in boxes with MAP box liners (LifeSpan L316, FF-602, and FF-504). Percentage of healthy fruit was unaffected by any of the treatments during the ripening period (shelf life) after 45 days of cold storage. However, after 60 days of cold storage, fruit from the MAP box liners with higher CO2 and lower O2 levels had a higher incidence of chilling injury (CI) symptoms, evident as flesh translucency, gel breakdown, and “off flavor” than fruit from the other treatments. Overall, results indicate that the use of MAP box liners is recommended to improve market life of ‘Friar’ plums up to 45 days cold storage. However, the use of box liners without gas control capability may lead to CI symptoms in fruit cold-stored for longer periods.
This paper describes a moderately high-density orchard training system (1000 trees/ha) developed at the Univ. of California's Kearney Agricultural Center for peach and nectarine trees grown on standard rootstocks. This two-leader system was developed to increase production during the early years of the orchard while minimizing specialized management operations during orchard maturity. Early selection of two primary scaffolds oriented perpendicular to the tree row is recommended during the first season of growth. During subsequent years, summer and dormant pruning requirements are similar to the standard open-vase system grown in California. Because of the uniform and relatively simple tree structure, individual scaffolds, rather than whole trees, can be used as functional units for crop load management.
Brown discoloration of the core, carpels, and flesh areas of `Ya Li' and `Seuri' Chinese pears [Pyrus bretschmeideri (Rehd.)] depended on harvest date. Fruit harvested no later than 180 days after full bloom (3000 degree days) did not develop the disorder. Browning of the core and flesh tissues increased when cooling was delayed, but was not influenced by subsequent storage temperatures of 0,10, or 20C. In both cultivars, the onset of internal browning was evident after storage in fruit that had been harvested when skin color had changed from green to light green-yellow. Thus, skin color can be used to determine harvest date to avoid internal browninincidence during storage of `Ya Li' and `Seuri' Chinese pears.
A commercial controlled delayed cooling or preconditioning treatment was developed to extend peach (Prunus persica) market life of the most popular California peach cultivars. A 24 to 48 h cooling delay at 68 °F (20.0 °C) was the most effective treatment for extending market life of internal breakdown susceptible peaches without causing fruit deterioration. This treatment increased minimum market life by up to 2 weeks in the cultivars tested. Weight loss and softening occurred during the controlled delayed cooling treatments, but did not reduce fruit quality. Detailed monitoring of these fruit quality changes during the delayed cooling period and proper use of fungicides is highly recommended for success in this new fruit delivery system. Rapid cooling after preconditioning is important to stop further fruit deterioration such as flesh softening, senescence, decay and weight loss. Controlled delayed cooling can also be used to pre-ripen susceptible and nonsusceptible peaches to deliver a ready-to-buy product to the consumer.