The color of fruits and vegetables results from the presence of chlorophyll, carotenoid, and anthocyanin pigments. Instrumental measurements of color are used routinely in describing processes of changing color, such as fruit ripening. The applicability of using skin color measurements to predict changes in pigment composition was investigated using a wide range of fruit and vegetables. Skin color was measured using a Hunter Colorlab and represented as the coordinates X, Y, Z, L*, a*, b*, chroma (C*), and hue angle (ho). Identical skin samples were extracted and analyzed for chlorophyll, carotenoid, and anthocyanin concentration. Sets of pairwise scatter plots were generated for each set of color variables and for the chlorophyll, anthocyanin, and carotenoid pigments. There were linear relationships between ho and anthocyanin concentration and between L* and log [chlorophyll concentration]. Multiple regressions for each pigment variable and sets of color variables also were calculated. However, there was no unique linear combination of pigments that gave rise to a unique point in the color space. Conversely, a given set of coordinates in the color space can be accounted for by many combinations of pigments. Therefore, a given color measurement cannot be described in terms of a unique combination of pigments. Caution is urged in interpreting tristimulus color coordinates in terms of a simple change in pigment composition without prior knowledge of the pigment composition within the fruits and vegetables. The surface topography of fruits and vegetables may be of considerable significance in measuring color.
Jane E. Lancaster, Carolyn E. Lister, Peter F. Reay, and Christopher M. Triggs
Peter M. Hanson, Ray-yu Yang, Jane Wu, Jen-tzu Chen, Dolores Ledesma, Samson C.S. Tsou, and Tung-Ching Lee
Tomato (Lycopersicon esculentum Mill.) is among the most widely consumed vegetables worldwide and an important source of certain antioxidants (AO) including lycopene, β-carotene, and vitamin C. Improvement of tomato for content of AO and overall antioxidant activity (AOA) could potentially benefit human health in many countries. We evaluated 50 L. esculentum and three L. pimpinellifolium (L.) Mill. entries for contents of lycopene, β-carotene, ascorbic acid, total phenolics, and two assays for antioxidant activity [anti-radical power (ARP) and inhibition of lipid peroxidation (ILP)] for 2 years during the same period in south Taiwan. We detected high levels of genetic diversity for the AO and AOA measured in this study. Group means of the L. pimpinellifolium entries were significantly higher than L. esculentum group means for ARP, ILP, lycopene, ascorbic acid, phenolics, and soluble solids concentration, suggesting that introgression of alleles from L. pimpinellifolium may have potential to improve cultivated tomato for these traits. Ranking of entries for ILP and ARP were consistent between years, particularly for those entries with the highest means and these assays could be adopted by tomato breeders. Results from ILP and ARP assays were highly correlated (r = 0.82**) and it would be unnecessary to use both assays for tomato. Lycopene, β-carotene, ascorbic acid, soluble solids, and total phenolics were all positively correlated with ARP. Among AO, total phenolics content was most closely associated with ARP (r = 0.90**) and ILP (r = 0.83**); this suggests that phenolics make a major contribution to AOA in tomato fruit. Fruit size was negatively correlated with ARP (r = -0.74**) and ILP (r = -0.71**), indicating that combining large fruit size and high AOA will be challenging.
Philipp W. Simon and John P. Navazio
Kathleen G. Haynes
Although potato (Solanum tuberosum L.) tuber yellow flesh per se is known to be controlled by a single gene, the intensity of yellow flesh varies widely in Solanum L. species. Many diploid species have very intense yellow flesh, as compared to the commercial tetraploid yellow-flesh cultivar `Yukon Gold'. Inheritance of yellow-flesh intensity at the diploid level was investigated in a hybrid population of S. phureja ssp. phureja (Juz. & Buk.)-S. stenotomum ssp. stenotomum (Juz. & Buk.) (PHU-STN). Six randomly chosen male parents were crossed to five randomly chosen female parents in a Design II mating scheme. In 1993, ≈12 progeny (clones) from each of the 30 families were planted in a randomized complete block design with two replications in Presque Isle, Maine, and evaluated for tuber yellow-flesh intensity as measured by a reflectance colorimeter. Twenty-five tubers from each plot were scored using the YI E-313 yellow intensity scale. An average YI E-313 score was obtained for each plot. Narrow-sense heritability on a plot mean basis was estimated as 0.99 with a SE of 0.65 to 0.72. There were significant differences among clones within a family. Results suggest that rapid progress can be made in breeding for intense yellow flesh in this diploid population. Clones from this population that produce 2n gametes represent an important source of germplasm for enhancing the intensity of the yellow-flesh trait in tetraploid potatoes.
Kathleen G. Haynes, William E. Potts, Jesse L. Chittams, and Diane L. Fleck
For the yellow-flesh fresh market, potato (Solanum tuberosum L.) varieties with intense yellow flesh are desired. Twenty-five yellow-flesh clones, including 24 U.S. Dept. of Agriculture (USDA) selections and the check variety `Yukon Gold', were evaluated for tuber yellow-flesh color, as measured by a reflectance colorimeter, and for individual tuber weight in replicated field trials in Presque Isle, Maine, in 1991 and 1992. There were significant differences among clones for yellow-flesh intensity. Yellow-flesh intensity in two USDA selections was significantly less than in `Yukon Gold'. In four USDA selections, yellow-flesh intensity was significantly greater than in `Yukon Gold'. In general, there was an inverse relationship between tuber weight and yellow-flesh intensity. Subsamples of tubers whose weight fell between the 10 to 90, 25 to 75, 35 to 65, and 40 to 60 percentile were compared to the full sample. There was good agreement between the 10 to 90 and 25 to 75 percentile subsample and the full sample regarding the average yellow-flesh intensity and in the consistency of pairwise comparisons between individual selections and `Yukon Gold'. For determining yellow-flesh intensity, the 25 to 75 percentile subsample was as informative as the full sample.
R.J. Griesbach, F. Meyer, and H. Koopowitz
Embryo rescue was successfully applied to develop hybrids between Ornithogalum dubium Houtt. (short inflorescence with orange flowers) and O. thyrsoides Jacq. (tall inflorescences with white flowers]. Meiosis in these hybrids showed abnormalities such as univalents, laggards, and bridges. The F, hybrids were partially fertile, and F2 and BC1 progeny were produced. The backcross hybrids segregated for flower color and, inflorescence traits and introgressed seedlings with orange pigmented flowers on tall inflorescences were obtained in the population.
M. Radi, M. Mahrouz, A. Jaouad, M. Tacchini, S. Aubert, M. Hugues, and M.J. Amiot
Phenolic composition and susceptibility to browning were determined for nine apricot (Prunus armeniaca L.) cultivars. Chlorogenic and neochlorogenic acids, (+)-catechin and (-)-epicatechin, and rutin (or quercetin-3-rutinoside) were the major phenolic compounds in apricots. In addition to these compounds, other quercetin-3-glycosides and procyanidins have been detected. Chlorogenic acid content decreased rapidly during enzymatic browning, but the susceptibility to browning seemed to be more strongly correlated with the initial amount of flavan-3-ols (defined as catechin monomers and procyanidins). As chlorogenic acid is certainly the best substrate for polyphenol oxidase, the development of brown pigments depended mainly on the flavan-3-ol content.
Haejeen Bang, Sunggil Kim, Daniel I. Leskovar, Angela Davis, and Stephen R. King
Gene identification and characterization can be utilized for the identification of respective functions and their relationship to flesh color inheritance. Phytoene synthase (PSY), which converts two molecules of GGPP into phytoene, is the first committed step of the pathway. Previous phylogenetic analysis of PSY has indicated that PSY duplication is common in Poaceae, but rare in dicots. Degenerate PCR and RACE were used for PSY cloning. Three members of PSY gene family (PSY-A, PSY-B and PSY-C) were identified. PSY-A shared higher identity with PSY-C than PSY-B. PSYC shared 96% identity with melon PSY. PSY-C also showed a high homology with tomato PSY1, even higher than PSY-A and PSY-B. It showed a similar gene expression pattern, so we propose that PSY-C is a homologue to PSY1. RT-PCR analysis indicated that PSY-B has a different transcriptional behavior from PSY-A, similar to tomato PSY2. Therefore, PSY genes appear to be under different regulatory mechanisms. Deduced protein sequence of PSY1 or PSY2 between species has higher homology than between PSY1 and PSY2 within species. Phylogenetic analysis indicated that watermelon PSY gene family is very distantly related. Watermelon and carrot PSY gene families did not appear to cluster as closely as in Poaceae or tomato. This indicates that watermelon and carrot PSY genes are not conserved as much as PSY in tomato or Poaceae. There was no particular pattern in phylogenetic relationship of dicots. Poaceae PSY genes showed a clustering into a PSY1 group and PSY2 group. PSY duplication in watermelon provides additional evidence that PSY duplication may be a common phenomenon in dicots. They are likely to be duplicated evolutionarily a long time ago, possibly even prior to the evolution of monocot and dicot divergence.