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T.E. Young, J.A. Juvik, and J.G. Sullivan

To identify qualitative and quantitative chemical variation in tomato fruit dry matter, crosses were made between the high soluble solids concentration (SSC) line LA 1501 (6.3% SSC when red-ripe) and the nearly isogenic commercial tomato cultivar VF 145B-7879 with a lower SSC (4.4% when red-ripe). Fruit samples from the parents and the reciprocal F1 hybrids were collected at 3-day intervals, from 25 to 52 days after anthesis, to evaluate the accumulation of various quality components throughout the development of the fruit from immature-green to red-ripe stage. Fructose and glucose concentrations, titratable acidity, pH, and percent dry weight (pulp and serum) were determined for each sample on a fresh basis. Fruit maturity was evaluated by puree color using Hunter `a' colorimeter values. Changes in most of the chemical constituents of the fruit were found to regress linearly with changes in fruit color. Regression of puree color against fruit SSC, and fructose, glucose, and total sugar concentrations described more of the observed variability in these components than days after anthesis, indicating that Hunter `a' colorimetric values provide a more precise measurement of fruit physiological age. The variation between the parents in fruit dry matter was found to be primarily due to differences in SSC. The ratio of fruit soluble to total solids concentration increased 23.7% in LA 1501 (from 61.6% to 85.3%) throughout ripening compared to-an increase of only 8.9% (from 66.3% to 75.2%) in `VF 145B-7879'. At the red ripe stage, LA 1501 possessed a 44% higher SSC than `VF 145B-7879'. Differences in fructose and glucose accounted for 41% of the variation in SSC between the two lines. An unidentified component(s) was responsible for the residual variation. Application of the genetic and physiological information generated from this study can be used to isolate and select for genes controlling accumulation of tomato fruit dry matter.

Open access

Zena Rawandoozi, Timothy Hartmann, David Byrne, and Silvia Carpenedo

environment in peach-tree canopies influence fruit-quality HortScience 26 1464 1466 Crisosto, C.H. Crisosto, G.M. 2005 Relationship between ripe soluble solids concentration (RSSC) and consumer acceptance of high and low acid melting flesh peach and nectarine

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Roisin McGarry, Jocelyn A. Ozga, and Dennis M. Reinecke

Field experiments were conducted on two cultivars of saskatoon to test the effectiveness of ethephon in stimulating uniform fruit ripening without compromising fruit quality. Shrubs of cultivars Northline and Smoky were sprayed to runoff with ethephon (0, 250, 500, and 1000 mg·L-1 for `Northline'; 0, 500, and 1000 mg·L-1 for `Smoky') prior to fruit maturity. Fruit were harvested 4 to 8 days after treatment and sorted into ripeness categories by size, and the fully ripe fruit were evaluated for quality (surface color, firmness, mean fruit weight, soluble solids, and titratable acids). Ethephon significantly increased the percent ripe fruit per shrub (by up to 9.7%) in both cultivars, without a significant effect on fruit quality. At concentrations up to 1000 mg·L-1, ethephon may be an effective ripening agent for saskatoon fruit without reducing fruit quality. Although there were significant differences in yield from year to year for both cultivars because of their biennial-bearing habit, ethephon treatments did not significantly affect total yields.

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M.E. Saltveit

Tomato fruit undergo an orderly series of physiological and morphological changes as they progress from mature-green (MG) to red-ripe. Fruit are commercially harvested at the MG stage, a stage which often encompasses fruit of varying degrees of maturity. The ability to predict the time required for MG fruit to ripen would reduce variability in experiments and could be commercially used to pack fruit that would ripen uniformly. Nuclear magnetic resonance (NMR) imaging can nondestructively measure internal changes associated with plant growth and developmental. In this study, NMR images were taken of freshly harvested tomato fruit (Lycopersicum esculentum cv. Castlemart) at different stages of maturity and ripeness. Measurements were also made of the stage of ripeness, rate of respiration and ethylene production, lycopene and chlorophyll content, density of the pericarp wall, and condition of locular tissue. NMR images showed substantial charges in the pericarp wall and locular tissue during maturation and ripening of tomato fruit. However, it was difficult to objectively evaluate these visual changes with other ripening parameters. For example, increased lightness and graininess of the pericarp wall image was associated with a decrease in wall density; while lightening of the locular image was associated with tissue liquefacation. Use of NMR imaging in studies of tomato fruit ripening will be discussed.

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Yunxia Qiu and Robert E. Paull

Over ripe and abnormally soft fruits occur often during papaya shipments to the mainland U.S.A. Calcium fertilization to the soil did not always increased Ca concentration in the mesocarp. Calcium plus K treatment was more effective at increasing the Ca concentration in the mesocarp than Ca treatment alone. Calcium and K fertilization did not affect the fruit color development. There was a positive correlation between mesocarp Ca concentration and ripe fruit firmness, with no relationship between K or Mg concentration and ripe fruit firmness. Vacuum infiltration with CaCl2, MgCl2, KCl to mesocarp plugs in vitro showed that Ca significantly delayed softening and reduced C2H4 production, and that MgCl2 and KCl also slowed the softening. Use of the chelating agent sodium citrate increased the rate of softening, probably, by removing Ca from the cell wall. We conclude that Ca is an important factor in fruit firmness and that the increase of Mg and K by infiltration has different effects on fruit firmness from that by soil fertilization.

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R. Koslanund, D.D. Archbold, and K.W. Pomper

Pawpaw (Asimina triloba L.), the largest tree fruit native to North America, has become the focus of a significant effort to develop its commercial potential. Due to the very short shelf life of the ripe fruit, a critical component of this effort is the establishment of appropriate harvest and postharvest storage techniques. Although it has been reported that the ripening of the fruit is climacteric, there is no published data to support this. Nor are there any reports on the response of the fruit to cold storage. Fruit were harvested and classified as unripe if no softening was evident or as ripe if softening had commenced. Fruit were held at room temperature or were stored at 4 °C for 28 days, then moved to room temperature. Ripe fruit exhibited respiratory and ethylene climacteric peaks within 3 days of harvest and 5 to 7 days after removal from cold storage. Unripe fruit exhibited climacterics 5 days after harvest and after removal from cold storage. A survey of drops indicated that they were postclimacteric. Thus, pawpaw is a climacteric fruit and cold storage delays the start but not the relative rate of ripening.

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David M. Francis, Sheryl A. Barringer, and Robert E. Whitmoyer

Yellow shoulder disorder (YSD) is characterized by sectors of yellow or green tissue under the peel of uniform ripening tomato (Lycopersicon esculentum Mill.) fruit. Tissues excised from sectors of fruit expressing YSD, from adjacent red sectors, and from mature green fruit were used to compare the ultrastructural alterations in cells and tissue affected by YSD and to determine whether the disorder is caused by delayed fruit maturation or by aberrant development. Cells from YSD sectors were smaller than those from both adjacent red-ripe tissue and mature green fruit. The smaller cells from the YSD sectors were at a different developmental stage than cells of the adjacent red-ripe tissue. Chromoplasts in red-ripe tissue were more advanced in development than those in YSD sectors or mature green fruit. Using the transition from chloroplast to chromoplast and the degradation of the middle lamella between adjacent cells as developmental markers, the maturity of tissue from YSD sectors appeared to be equal or greater than that of tissue from mature green fruit. However, cell enlargement, which takes place early in fruit development, was retarded in YSD sectors. Therefore, the ultrastructural features of YSD are not compatible with a delayed ripening model for this blotchy ripening disorder. These observations provide a basis for comparing YSD in uniformly ripening tomatoes with other blotchy ripening disorders.

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Nazir A. Mir, Najma Khan, and Randolf M. Beaudry

The effects of 1-MCP on ripening and shelf life in fruit of five classes of maturity (1, mature green; 2, turning; 3, half-ripe; 4, ripe; and 5, over-ripe) of `Plum' tomato (Lycopersicon × esculentum, Mill) at 22 °C were evaluated. 1-Methylcylopropene (1-MCP) reduced the rate of red color development in fruit of all maturity classes. However, the effect was more discernable in fruit with higher hue angle value. Single application of 1-MCP delayed the color development by 10 days. While a second application of 1-MCP at day 10 delayed color development by another 10 days for mature green tomatoes, it did not influence the color change in all other classes of maturity. The effects of 1-MCP on firmness loss were similar to color development. Compared to the control, 1-MCP reduced the ripening-related rate of respiration by approximately 40%. Contrary to this, ethylene production was not affected by 1-MCP application. Potential exists to use 1-MCP in tomato to reduce ethylene-associated changes in texture and color.

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Shiow Y. Wang and Hsin-Shan Lin

Fruit and leaves from different cultivars of thornless blackberry (Rubus sp.), red raspberry (Rubus idaeus L.), black raspberry (Rubus occidentalis L.), and strawberry (Fragaria × ananassa D.) plants were analyzed for total antioxidant capacity (oxygen radical absorbance capacity, ORAC) and total phenolic content. In addition, fruit were analyzed for total anthocyanin content. Compared to fruit, leaves were found to have higher ORAC values. In fruit, ORAC values ranged from 7.8 to 33.7 μmol Trolox equivalents (TE)/g of fresh berries, while in leaves, ORAC values ranged from 20.8 to 45.6 μmol TE/g of fresh leaves. Fruit harvested at different stages of maturity were analyzed in blackberries, raspberries, and strawberries. Blackberries and strawberries had their highest ORAC values during the green stages, while raspberries generally had the highest ORAC activity at the ripe stage (with exception of cv. Jewel, a black raspberry). Total anthocyanin content increased with maturity for all three fruit. There was a linear correlation existed between total phenolic content and ORAC activity for fruit and leaves. For ripe berries, there was also a linear relationship between ORAC values and anthocyanin content. Of the ripe fruit and leaves tested, raspberry plants appeared to be the richest source for antioxidants.

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Nazir Mir, Mauricio Canoles, Randolph Beaudry, Elizabeth Baldwin, and Chhatar Pal Mehla

The capacity for 1-methylcyclopropene (1-MCP) to inhibit color change and firmness loss and alter aroma profiles for tomato (Lycopersicon esculentum Mill.) fruit was evaluated as a function of 1-MCP concentration, multiple and continuous applications, and stage of ripeness. In addition, the relationship between external and internal fruit color and firmness was determined. 1-MCP reduced the rate of red color development in fruit of all stages of ripeness. A single application of 1-MCP delayed color development by ≈ days. A second application of 1-MCP 10 days after first treatment additionally delayed color development of mature green fruit by another 8 to 10 days. Continuous 1-MCP application completely inhibited color development of breaker and half-ripe fruit for the duration (34 days) of application, but only partially inhibited firmness loss. When fruit at 50% color development were treated with 1-MCP, gel color development tended to lag behind the external fruit color change compared to nontreated fruit. Some aroma volatiles were affected by 1-MCP applied at the mature green and breaker stages, but the effect was relatively minor; 1-MCP did not affect sugar or titratable acid levels in these fruit. Collectively, the data indicate 1-MCP caused minor shifts in the quality attributes of locule color, aroma, and firmness relative to external color, which may reduce the value of this treatment, but benefits accrued by slowed firmness loss and color development may afford sufficient compensation to make 1-MCP application commercially feasible.