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Douglas V. Shaw and Erik J. Sacks

Four sets of selected strawberry (Fragaria ×ananassa Duch.) genotypes were generated from within a single breeding population to evaluate the correspondence between predicted and realized selection response for fresh fruit color traits. Genotypes were selected for extreme phenotypes, dark or light, of either internal or external color value (CIELAB L*). Genotypic selection response was evaluated empirically by scoring fruit from the clonal derivatives of these selected genotypes, and response for breeding value was estimated by scoring the offspring of crosses performed among a subset of the genotypes within each selected set. Realized selection response was slightly larger than predicted for internal and external L* when calculated for selected genotypes. Also, more than half of the selected genotypes had genotypic values for L* outside the range of the original parents, providing evidence for transgressive segregation. Realized selection response for breeding value in exterior and interior color was slightly less than predicted. Compared in a different way, genotypic selection response for external color was significantly greater than selection response for breeding value, whereas genotypic and breeding value responses did not differ for internal color. These observations suggest the presence of some nonadditive genetic variance for external color but support the conclusion that the heritabilities predicted previously were reasonably accurate. Estimates of variance components within each of the offspring populations demonstrated that genetic variances were modified substantially by one generation of selection. Selection for dark fruit color reduced genetic variance to nonsignificant levels, with internal color more affected than external color. The total genetic variances within both of the offspring populations from parents selected for light color were changed little by one generation of selection, but substantial dominance variance was detected that had not been found in the original population. The rapid response to selection and large changes in the distribution of genetic variances may indicate the presence of a few genes with comparatively large effect in strawberry color expression. Additional divergent selection response can be expected, but primarily in the direction of light fruit color.

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Patrick J. Conner and Dan MacLean

relatively uncommon in most clones. Attractive color is a main sensory characteristic of fruit products. Muscadine berries typically occur as a very dark purple or black color or as an unpigmented or lightly blushed bronze (greenish yellow) color

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Claudia Dussi, David Sugar, A. Azarenko, and T. Righetti

Fruit color of `Sensation' and `Max' Red Bartlett pears was analyzed once at mid-season and three times during later stages of fruit maturity with a Minolta CR-200b portable colorimeter. Color measurements were taken on sun-exposed and shaded fruit surfaces in three different growing locations in Oregon. Color change is nearly constant over time during fruit maturation. Both cultivars gained red and yellow on sun-exposed fruit surfaces, and lost red but gained yellow on shaded surfaces. `Sensation' gained red on sun-exposed surfaces to a greater extent than did `Max' at all locations. `Max' gained more yellow and lost more red on shaded surfaces than did `Sensation'. Differences between cultivars and locations were greater on shaded than on sun-exposed fruit surfaces. Greatest gain in both red and yellow on sun-exposed surfaces was associated with the warmest growing location. Visually perceived color change with maturity appears to be due both to loss of red on shaded surfaces and gain of yellow on all surfaces.

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C. Jasso-Chaverria, G.J. Hochmuth, R.C. Hochmuth, and S.A. Sargent

Two greenhouse cucumber (Cucumis sativus) cultivars with differing fruit types [European (`Bologna') and Beit-alpha (`Sarig')] were grown during two seasons in a perlite medium in black plastic nursery containers in a passively ventilated greenhouse in northern Florida to evaluate fruiting responses to nitrogen (N) fertilization over the range of 75 to 375 mg·L–1. Fruit production, consisting mostly of fancy fruits, increased quadratically with N concentration in the nutrient solution, leveling off above 225 mg·L–1 for both cucumber cultivars. Fruit length and diameter were not affected by N concentration in the nutrient solution. Leaf N concentration, averaged over three sampling dates, increased linearly with N concentration in the nutrient solution from 46 g·kg–1 with 75 mg·L–1 N to 50 g·kg–1 with 375 mg·L–1 N. Fruit firmness decreased with increasing N concentration and there was little difference in firmness between the two cultivars. Firmness was similar across three measurement dates during the spring harvest season, but increased during the season in the fall. Fruit color responses to N concentration were dependent on the specific combination of experiment, sampling date, and cultivar. For most combinations of experiment, sampling date, and cultivar, cucumber epidermal color was greener (higher hue angle) with increased N concentration. The color was darkest (lowest L* value) and most intense (highest chroma value) with intermediate to higher N concentrations.

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Cheryl R. Hampson, Harvey A. Quamme, Frank Kappel, and Robert T. Brownlee

The effect of increasing planting density at constant rectangularity on the fruit yield, fruit size, and fruit color of apple [Malus ×sylvestris (L) var. domestica (Borkh.) Mansf.] in three training systems (slender spindle, tall spindle, and Geneva Y trellis) was assessed for 10 years. Five tree densities (from 1125 to 3226 trees/ha) and two cultivars (Royal Gala and Summerland McIntosh) were tested in a fully guarded split-split plot design. Density was the most influential factor. As tree density increased, per-tree yield decreased, but yield per unit area increased. The relation between cumulative yield per ha and tree density was linear at the outset of the trial, but soon became curvilinear, as incremental yield diminished with increasing tree density. The chief advantage of high density planting was a large increase in early fruit yield. In later years, reductions in cumulative yield efficiency, and in fruit color for `Summerland McIntosh', began to appear at the highest density. Training system had no influence on productivity for the first 5 years. During the second half of the trial, fruit yield per tree was greater for the Y trellis than for either spindle form at lower densities but not at higher densities. The slender and tall spindles were similar in nearly all aspects of performance, including yield. `Summerland McIntosh' yielded almost 40% less than `Royal Gala' and seemed more sensitive to the adverse effects of high tree density on fruit color.

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W.J. Steyn, D.M. Holcroft, S.J.E. Wand, and G. Jacobs

2 Present address: DOLE Fresh Vegetables, P.O. Box 1759, Salinas, Calif. 93902. This material is based upon work supported by the National Research Foundation of South Africa under grant GUN: 2046844 and the Deciduous Fruit Producers Trust of South

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Suparna Whale*, Zora Singh, and John Janes

The effects of preharvest application of AVG and ethephon alone, or in combinations, on color development, fruit quality and shelf life were tested in `Pink Lady' apples (Malus domestica Borkh.) in Western Australia during 2002.The experiment aimed at improving color without adversely affecting fruit quality at harvest and after long term cold storage. Treatments included 124.5 g·ha-1 AVG only [148 Days after full bloom (DAFB)]; 280 g·ha-1 ethephon only (148 DAFB); AVG (148 DAFB) followed by ethephon (166 DAFB); and control. Fruit were evaluated for color development, internal ethylene concentration (IEC) and quality at commercial harvest(181DAFB) and 45, 90, and135 days after cold storage (1 °C ± 0.5 °C). At harvest, ethephon with or without AVG significantly (P ≤ 0.05) improved red blush and total anthocyanin in fruit skin. AVG+ethephon treated-fruit had higher total anthocyanin and TSS compared to AVG alone and control fruit. There were no significant differences among different AVG and ethephon treatments for fruit firmness and IEC. During different storage periods, fruit treated with AVG alone and AVG+ethephon had significantly lower IEC compared to fruit treated with ethephon only and the control, however the interactions between treatments and storage periods were not significant for fruit firmness. AVG + ethephon and ethephon alone did not significantly affect fruit color during different storage periods, which showed that the subsequent ethephon spray on AVG-treated fruit had overcome the inhibitory effect of AVG. Our experimental results showed that application of AVG followed by ethephon improved color in `Pink Lady' apples without compromising fruit quality including firmness during extended cold storage.

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Brandon M. Hurr, Donald J. Huber, and James H. Lee

Research (T-STAR). Special thanks to West Coast Tomato Inc. and Pacific Tomato Inc. for supplying tomato fruit.

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Eileen Kabelka, Wencai Yang, and David M. Francis

An inbred backcross (IBC) population derived from Lycopersicon hirsutum LA407 and L. esculentum was evaluated in replicated field trials to assess its potential for the improvement of red-fruited tomatoes. Significant phenotypic variation among genotypes was detected for the hue (tint), L (darkness), and chroma (saturation) of color. Significant effects due to environment and genotype × environment interactions also were observed. One superior inbred backcross line from this population, IBL 2349, was used to develop an F2 population and to explore the genetic basis of color. Two independent L. esculentum quantitative trait loci (QTL) associated with improved color were identified based on linkage to markers mapping to chromosome 4 and chromosome 11. Epistatic interactions were identified between the two L. esculentum loci. Unexpected epistatic interactions also were identified between L. esculentum loci and an LA407 introgression on chromosome 7 present within IBL 2349. The two L. esculentum QTL and the epistatic interactions were confirmed in replicated trials with F3 and F4 families. The loci identified in this study and their epistatic interactions may provide additional tools for the improvement of red-fruited tomatoes in breeding programs.

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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.