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Jack E. Staub and John P. Navazio

A study was designed to determine whether temperature alone or temperature and relative humidity (RH) interactions affect the development of pillowy fruit disorder (PFD) in cucumber (Cucumis sativus L.). Fruit of `Calypso', `Flurry', `Carolina'? and inbred breeding line 39 were matured in four environments: cyclic and high (22 to 45C) and moderate (22 to 30C) temperatures at two RHs (35% and 75%). PFD symptoms were most severe at high temperature and RH; thus, both contribute to the development of this disorder. Line 39 had the highest PFD ratings, regardless of growing environment, a result indicating that cultigens respond differently to these imposed stresses.

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Sylvia M. Blankenship and L. Eric Hinesley

Fraser fir [Abies fraseri (Pursh) Poir.] branches were held at 5C for 4 to 6 weeks in the following atmospheres: 1% or 3% in nitrogen; 0%, 1%, 5%, 10%, 20%, 40%, or 50% CO2 in air; or air only. Experiments were conducted in two. years during the fall, winter, and early spring. In general, CO2 ≥ 5% accelerated needle loss. There was considerable tree-to-tree variation in tolerance to elevated CO2. Oxygen at 1% killed branches, and 3% O2 showed no benefit compared to air. The initial dark respiration rate at 21C was about four times higher than at SC. Respiration decreased for ≈ 10 days and stabilized at 14% to 20% of the initial values. Respiration increased exponentially with increasing temperature between 5 and 27C. Short-term controlled or modified atmosphere storage would probably not be useful in improving the postharvest handling of Fraser fir.

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A.P. Medlicott, Mayé N'Diaye, and J.M.M. Sigrist

The effects of acetylene at 0, 0.1, 0.2, 0.4, 0.8, or 1.6 ml·liter-1 and exposures of 4, 8, 12, or 24 hours on ripening initiation In mangos (Mangifera indica L.) harvested at three stages of maturity were investigated: Ripeness was assessed before and after treatment in `Tommy Atkins', `Ruby', and `Amelie' mangos by analysis of texture, peel, and pulp color development, soluble solids concentration, and pH. The initiation of ripening depended on the acetylene concentration, exposure time to acetylene, the physiological maturity of the fruit at harvest, and on the cultivar. Changes that can occur during ripening bad different sensitivities to acetylene gas. Acetylene treatment of 0.1 or 0.2 ml·liter-1 for 24 hours at 25C initiated softening, but had no effect on the other ripening processes measured. All the ripening changes measured were initiated with a 24-hour exposure to 0.4 ml·liter-1 in `Tommy Atkins', while 0.8 ml·liter-l was required with `Ruby' mangos. There was an interaction between gas concentration and exposure time taken to Initiate ripening. The 0.8 ml·liter-1 acetylene treatment required 24 hours to initiate full ripening, while 8 hours were required with 1.6 ml·liter-l acetylene and 1.0 ml·liter-1 ethylene. Mature and half-mature fruit showed a similar response to gas treatments; immature fruit failed to show full ripening initiation, although softening and peel color development were enhanced.

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L.E. Hinesley and Sylvia M. Blankenship

Several floral and tree preservatives were evaluated to determine their effect on postharvest needle retention of Fraser fir [Abies fraseri (Pursh) Poir.], an important Christmas tree species. Clorox (sodium hypochlorite) and aspirin (salicylic acid) caused massive needle loss, and three of the six commercial additives increased needle loss significantly, No treatment was better than water alone.

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O.L. Lau

In a 2-year study, the benefits and risks of an initial low O2 stress treatment (ILOS; 0.04 kPa O2 for 10 days) as a supplement to 1.5 or 0.7 kPa O2 storage for controlling scald in `Starkrimson Delicious' apples (Malus ×domestica Borkh.) were evaluated. The fruit were picked from 15 orchards and harvested over five successive weeks to generate a wide range in maturity. Storage in 0.7 kPa O2 did not adequately control scald in fruit picked at starch index between 1.0 and 2.1 (10% to 35% scald), but reduced watercore-induced breakdown in fruit picked at starch index ≥2.4 (0–9 scale). The ILOS treatment gave a statistically significant but commercially nonsignificant scald control benefit to fruit held in 1.5 kPa O2 in 1 year, but not to fruit held in 0.7 kPa O2. ILOS did not increase alcoholic taste, but increased skin purpling in 0.7 kPa O2-stored fruit from the final harvest in 1 year. ILOS decreased flesh firmness in fruit picked at starch index ≥1.7 and increased watercore-induced breakdown in fruit picked at starch index ≥2.1 in both years.

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Kathleen Evensen, Philip Hammer, Robert Crassweller, George Greene, and Laura Lehman-Salada

We present a method for predicting firmness of `York Imperial' apples after air or controlled-atmosphere storage. Firmness and soluble solids content in freshly harvested fruit can be plotted on a graph showing a “decision line.” If the prestorage firmness and soluble solids coordinates for a given sample are above the decision line, then firmness after storage is predicted to be greater than the target value. Prestorage flesh firmness and soluble solids content were the best predictors of poststorage firmness. There was no significant improvement in firmness prediction when ethylene, starch, or other indicators of maturity were included.

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Jeanine M. Davis and Randolph G. Gardner

Eight staked, determinate tomato (Lycopersicon esculentum Mill.) cultivars were harvested when green (before breaker stage) or when pink (breaker stage and riper) in two replicated field studies. In general, total yield and average fruit size were reduced when fruit were harvested at the green stage. Harvest maturity had only a small effect on occurrence of most fruit defects, except fruit cracking, which was more severe for pink than for green fruit in the early season experiment. Although total yields for pink harvested fruit were higher than for green harvested fruit in the early season study, the high incidence of fruit crack in pink fruit resulted in similar yields of U.S. combination grade (U.S. no. 1 and U.S. no. 2) fruit for both treatments. Because the largest fruit often bring a premium price, harvesting fruit when pink probably will result in a higher price per kilogram than harvesting fruit when green. Fruit harvested green, however, are generally firmer, more crack resistant, and require fewer harvests than fruit harvested pink.

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Sunita Kochhar, Christopher B. Watkins, Patricia L. Conklin, and Susan K. Brown

The activities and isoenzyme patterns of guaiacol-dependent peroxidase (POX), ascorbate peroxidase (APX), superoxide dismutase (SOD) and catalase (CAT) were studied in yellow- and red-fruited crab apple [Malus (L.) Mill.] selections from a `White Angel' × `Rome Beauty' cross that show differential susceptibility to the physiological storage disorder, superficial scald. There were no consistent relationships between total enzyme activities and scald incidence, high activities of the enzymes being detected in selections with both high and low susceptibilities to scald. However, additional individual isoforms of some antioxidant enzymes were detected in the scald-resistant selections when compared with scald-susceptible selections. In a native gel system, four guaiacol-dependent POX isoenzymes were detected in both yellow and red scald-resistant selections compared with only two in scald-susceptible selections. Similarly, for anodic acidic POX assayed using benzidine, six isoenzymes were detected in both yellow and red scald-resistant selections compared with five in yellow and four in red susceptible selections. Ten SOD isozymes were detected in scald-resistant yellow-fruited selections compared with only five faint bands in scald-susceptible selections, but similar patterns were not detectable for red-fruited selections. Differences in the presence of various isoenzymes for CAT and APX were also detected among the selections, but associations with scald susceptibility were also affected by fruit color or were inconsistent. The presence or absence of individual isoenzymes may be a better indication of scald resistance or susceptibility than the total enzyme activities. Isoenzyme analyses, especially of POX, could be useful to breeders for the early detection of scald resistance/susceptibility in apples.

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Shiow Y. Wang and Miklos Faust

Ethylene biosynthesis and polyamine content were determined in normal and watercore-affected apple (Malus domestics Borkh. cv. Delicious). Fruit with watercore produced more ethylene and contained higher amounts of putrescine (PUT), spermidine (SPD), 1-aminocyclopropane-1-carboxylic acid (ACC), and 1-(malonylamino) cyclo-propane-1-carboxylic acid (MACC). The activities of ACC synthase and ethylene-forming enzyme (EFE) in watercore-affected fruit were also higher than in normal fruit. The EFE activity in severely affected flesh was inhibited, resulting in ACC accumulation and low ethylene production. S-adenosylmethionine (AdoMet) was maintained at a steady-state level even when C2 H4 and polyamides were actively synthesized in normal and affected fruit.

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Errol W. Hewett and Christopher B. Watkins

The incidence of external and internal bitter pit in `Cox's Orange Pippin' apple (Malus domestics Borkh.) fruit sprayed with normal therapeutic sprays either with or without Ca salts at 2-week intervals during the growing season was determined after 6 weeks of storage over 7 consecutive years. Following harvest, fruit was either vacuum-infiltrated with CaCI2 or received no further treatment. Although there was a tendency for fruit that had been sprayed and vacuum-infiltrated with Ca to exhibit the greatest degree of bitter pit control, this treatment was not significantly superior to Ca sprays alone. Vacuum infiltration alone reduced the disorder to a lesser extent than Ca sprays and was more effective in reducing external than internal bitter bit. The results suggest that Ca applications over the growing season are superior to postharvest vacuum-infiltration with Ca in the prevention of bitter pit.