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Erik J. Sacks and Douglas V. Shaw

Color change in fresh, ripe strawberry (Fragaria ×ananassa Duch.) fruit stored at 0C for up to 7 days was recorded using the Commission Internationale de l' Éclairage color space (L*, a*, and b*). External (skin) fruit color became darker and less chromatic but did not change hue. Internal (flesh) fruit color became darker and more chromatic. Regression coefficients calculated for individual genotypes were homogeneous for each of the color traits except internal hue. Depending on genotype, the red fruit flesh either became a bluer red or did not change hue. In all cases, rates of change were small. Color change for fresh strawberry fruit during several days of storage at 0C likely is not an appreciable source of error in plant breeding experiments.

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C.E. Finn, J.F. Hancock, T. Mackey, and S. Serçe

Twenty blueberry (Vaccinium sp. L.) families were planted in Michigan and Oregon to determine variability among families, locations and the importance of family×location interaction. The families were generated at Michigan State University from crosses among parents with a diverse genetic background. Seedlings were planted in field locations in Corvallis, Ore., and East Lansing, Mich., in 1995 and managed following standard commercial blueberry production practices with no insecticide or fungicide applications. In 1998-2000 the plants were evaluated for survival, bloom date, ripening date, plant growth and the fruit were scored for crop load, color, picking scar, firmness and size. All traits, except fruit color, varied significantly between locations. Plants in Oregon had a 36% greater survival rate and grew to be much larger, 80% taller and 104% wider, than those in Michigan. Families in Oregon flowered earlier in the year than those in Michigan but ripened at a similar time. Between locations, family differences were only evident for survival and fruit color. In Oregon, there were differences among families for all traits whereas in Michigan only survival, ripening date, plant height and width, and picking scar differed significantly. The family × environment interaction was not significant for crop load, fruit color and fruit firmness, so individuals selected on the basis of crop load, fruit color and fruit firmness should perform similarly in either location. There was a significant family × environment interaction for the other traits including survival, bloom date, ripening date, ripening interval, plant height and width, and for picking scar. Therefore, there is a need for individual selection programs at each location. Genotypes well adapted to Michigan may also do well in Oregon, but numerous promising genotypes could be missed for Oregon, if families are first selected in Michigan. The loss of numerous individuals due to winter cold may have reduced levels of variability in Michigan.

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Ron Porat, Xuqiao Feng, Moshe Huberman, David Galili, Raphael Goren, and Eliezer E. Goldschmidt

'Oroblanco' is an early-maturing pummelo-grapefruit hybrid (Citrus grandis Osbeck × C. paradisi Macf.). The fruit are usually picked and marketed while the peel color is still green; however, in some cases they can lose this green color during postharvest shipping and storage, which diminishes their commercial value. The effects of storage temperatures, gibberellic acid (GA), ethylene, and 1-methylcyclopropene (1-MCP) on the degreening of 'Oroblanco' fruit were examined. Storage temperature was critical for retaining fruit color: at 2 °C the fruit remained green for a period up to 5 weeks, whereas at storage temperatures of 6, 12, and 20 °C there was a progressive increase in the rate of degreening. Applications of GA, either as preharvest sprays or as postharvest dip treatments, effectively retained the green fruit color. Ethylene exposures up to 100 μL·L-1 for 3 days had only a slight effect on fruit degreening, and 1-MCP treatments up to 200 nL·L-1 for 16 hours had no effect at all. The slight influence of ethylene and the ineffectiveness of 1-MCP on fruit color change can not be attributed to difficulties in their application, since in the same experiments ethylene markedly induced peduncle abscission, and 1-MCP effectively inhibited this ethylene effect. Accordingly, ethylene had only a relatively small effect on the induction of chlorophyllase enzyme activity in green 'Oroblanco' peel tissue.

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Harry S. Paris

The fruits of Cucurbita pepo cv. Table Queen are light green when young, turn dark green by intermediate age (15-18 days past anthesis) and remain dark green through maturity. Three major genes are known to affect developmental fruit color intensity in C. pepo: D, 1-1, and 1-2. Table Queen was crossed with cv. Vegetable Spaghetti and with tester stocks of known genotype in order to determine the genetic basis of its developmental fruit coloration. The results from filial, backcross. and testcross generations suggest that Table Queen carries gene D, which confers dark stem and fruit color from intermediate fruit age through maturity. Table Queen also carries L-2. which confers Light Type 2 (a pattern of grayish green hue) fruit color from intermediate age, but D is epistatic to L-2. The genotype of Table Queen is D/D 1-1/1-1 L-2/L-2. Clear-cut results were not obtained -- regarding the genetic basis of the retention of green color through maturity of Table Queen fruits.

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Stephen S. Miller and George M. Greene II

Replicated studies were conducted from 1996 to 1999 to evaluate the effect of a metalized reflective film (RF) on red color development in several apple (Malus ×domestica) cultivars that often develop poor to marginal color in the mid-Atlantic growing region. Film was applied to the orchard floor in the middle between tree rows or under the tree beginning 5 to 7 weeks before the predicted maturity date. Light reflected into the canopy from the RF was measured and compared with a standard orchard sod, a killed sod or various polyethylene films. Fruit color was estimated visually and with a hand-held spectrophotometer. Fruit quality (firmness, soluble solids, starch index) was determined from a representative sample of fruit. RF increased the level of photosynthetic photon flux (PPF) reflected into the canopy resulting in darker, redder colored `Delicious', `Empire', and `Fuji' apples with a greater proportion of surface showing red color. RF increased canopy temperature and fruit surface temperature. A white polyethylene film increased reflected PPF and fruit color, but generally not to the extent of the metalized RF. Large [>13 ft (4.0 m) height] well-pruned `Delicious' trees showed increased fruit color, especially when the RF was placed under the canopy, but `Empire' trees of similar size and a more dense canopy showed no effect. The effect of the RF was most pronounced in the lower portion [up to 8 ft (2.4 m) height] of the canopy. A high-density RF was as effective as a low-density RF and the high-density film was about 60% less expensive. A high-density RF may be a cost effective method to enhance red color on selected apple cultivars in the mid-Atlantic region. Comparisons between ethephon and the RF were variable: ethephon appeared to have more effect on color in `Empire' than the RF, but less effect than the RF on `Hardibrite Delicious'. Ethephon consistently advanced fruit maturity. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).

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Irene Kadzere, Chris B. Watkins, Ian A. Merwin, Festus K. Akinnifesi, John D. K. Saka, and Jarret Mhango

The full commercial potential of wild loquat [Uapaca kirkiana (Muell. Arg.)], a fruit that is widely used for food and income in parts of Africa, is restricted by its short shelf life and variability in postharvest quality. We have evaluated within and among tree variability in fruit size and color at harvest, and changes of color, soluble solids concentrations (SSC) and pulp deterioration during storage, of fruit harvested during the maturation period. The relationships between fruit shape, size, seed number and SSC of fruit harvested at the ripe stage of maturity was also assessed. Size and color of fruit within and among trees at harvest varied greatly within the same location on the same harvest date. The a* values (redness) were more variable than for other color attributes, reflecting a range of fruit colors from greenish to brown. During a 6 day storage period, fruit color lightness and yellowness decreased, while redness increased, and variation in color attributes decreased. Although fruit color intensified during storage, the SSC of fruit after ripening was linked more with fruit color at harvest, with mean concentrations ranging from 6.7% to 13.8% among trees. When fruit were harvested four weeks later and categorized by color at harvest, SSC varied from 11.8% in greenish-yellow fruit to 14.5% in browner fruit. Pulp deterioration of stored fruit harvested unripe was observed by 6 days. The SSC of fruit harvested when ripe was not significantly correlated with shape, size or seed number. These observations have important implications for germplasm selection and collection of U. kirkiana for domestication purposes. Timing of harvest and/or postharvest sorting of fruit is likely to reduce variability in SSC during the postharvest period.

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Naomi Porret, Peter Cousins, and Christopher Owens

Grapevine (Vitis vinifera L.) is one of our oldest domesticated crops and economically the most important cultivated fruit crop in the world. Cultivated grapes show substantial diversity in fruit color, including: varying shades of black, red, pink, grey, white, and types with pigmented berry flesh. The majority of V. vinifera cultivars only possess anthocyanin pigmentation in the skin of the berry (also known as teinturiers). However, some cultivars possess berries with intensely pigmented flesh as well as skin, which is often also associated with greater pigmentation of vegetative tissues. The genetic control and inheritance of fruit color in grapevine is poorly understood, despite evidence that the primary determination of anthocyanin production appears to be controlled by a single dominant locus in V. vinifera with white fruit being a recessive character. Recently, it has been shown that the presence of Gret1, a Ty3-gypsy-type retro-transposon in the promoter region of a myb-like regulatory gene is present in white-fruited cultivars of V. vinifera and that allelic variation in this gene associates with several qualitative classes of grape fruit color. It has been observed that the red-flesh berry phenotype is similarly controlled by a single dominant locus. Considering the association of variation in VvmybA1 with grape berry skin color, it was hypothesized that DNA sequence variation in VvmybA1 would also be associated with genotypes showing intensely pigmented berry flesh. In this study, we show that allelic variation in VvmybA1 associates with the teinturier phenotype both in a panel of accessions possessing red-flesh as well as in a population of full-sibs segregating for the red-flesh phenotype.

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Sylvia M. Blankenship, Edward C. Sisler, and Steven G. Russell

Mature green tomatoes (Lycopersicon esculentum Mill. cv. 674) were gassed with 160 to 275 μl/liter ethylene, depending upon the experiment, from either a Catalytic Generator or gas cylinder. Tomatoes were evaluated during subsequent ripening for fruit color development and taste. The combined results of two triangle difference taste tests indicated that the panel could tell a slight difference in taste of tomatoes based on gassing method. However, panelists did not reveal a strong preference for tomatoes from either method or consistently mention a certain characteristic that made the two groups of tomatoes different. Gas chromatographic analyses of the effluent from the Catalytic Generator indicated that several compounds other than ethylene were present.

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Martha A. Mutschler, David W. Wolfe, Edward D. Cobb, and Kenneth S. Yourstone

Fruit of tomato (Lycopersicon esculentum Mill.) hybrids heterozygous for the alc ripening mutation stored on average 60% (3.6 days) longer at 20C than that of their normal-ripening parents. There were no detrimental effects of the alc heterozygous condition on fruit color, firmness, or size. The background into which alc was introduced also affected fruit quality and shelf life. These results indicate hybrids heterozygous for the alc ripening mutant can produce commercially acceptable fruit with significantly longer shelf life than their normal-ripening parents.

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Kathy Kelley and Carol Regusci

Apogee at rates of 125 and 250 ppm applied at 2-cm average shoot growth and a split application of 125 ppm applied at 2-cm shoot growth and 2 weeks later reduced vegetative growth of `Pink Lady', `Gala', and `Fuji' in 1997 and 1998. Cultivar response varied with rate and year. Fruit size was significantly increased in `Gala' at the low rate and split low rate applications and in `Fuji' at the low and high rate single application in 1998. There was no effect on return bloom or fruit color.