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Peter J. Mes*, James R. Myers, and Balz Frei

A nutritional study was initiated to determine which carotenoids found in tomato result in decreased lipid oxidation ex vivo. To compare the carotenoids in a human diet without the use of purified supplements, tomatoes expressing nonfunctional enzymes in the carotenoid pathway were used. Tomato lines carrying the genes t, B, ogc, Del, or r were grown to produce fruit containing with high levels of prolycopene, beta-carotene, lycopene, or delta-carotene respectively, or low total carotenoids in r. Juices were processed from these lines and used in a dietary intervention study. Plasma samples were drawn before and after consumption of each juice. These samples were subjected to a battery of tests to analyze the contribution of carotenoids to the total lipid antioxidant status. Results of these tests are discussed.

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Brian J. Just* and Philipp W. Simon

While the carotenoid biosynthetic pathway has been studied several horticultural and agronomic crops, very little information exists for this conserved pathway in carrot, a primary source of dietary carotenoids. Though orange carrots are the most familiar color to Western consumers, yellow, red, and white carrots also exist and have been historically important. Modern carrot breeders are showing renewed interest in these unusual color phenotypes. Beta- and alpha-carotene are the primary pigments in orange carrot roots. Yellow carrots accumulate xanthophylls (oxygenated carotenes), red carrots accumulate lycopene (the precursor to alpha- and beta-carotene), and white carrots accumulate no detectable pigments. Differences between these phenotypes are usually monogenic or oligogenic. Our research has focused on identifying putative genes for carotenoid biosynthetic enzymes in the carrot genome, mapping them, and examining expression patterns in various tissues and carrot root pigment phenotypes. We are using this information to create a carrot pigment biosynthesis function map incorporating biosynthetic enzymes, major carrot color genes, and gene expression information.

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Evdokia Menelaou, Armen Kachatryan, Jack N. Losso, Michael Cavalier, and Don La Bonte

Fresh leaves of 6 sweetpotato (Ipomoea batatas [L.] Lam.) genotypes, `Beauregard', `Bienville', L99–35, L00–8, L01–145, and L01–29, were characterized for lutein. Lutein is a carotenoid capable of delaying blindness-related macular degeneration. The content of lutein in sweetpotato ranged from 0.38 to 0.58 mg·g–1 fresh weight. Beta-carotene separated from lutein on high-pressure liquid chromatograms and when spiked in pure lutein extract did not interfere with lutein separation. High-resolution electro-spray ionization mass spectrometric analysis was used to confirm the presence of lutein in sweetpotato leaves. Stems were also characterized and found not to contain lutein. Our results showed that sweetpotato leaves are an excellent source of dietary lutein and surpass levels found in leafy crucifers. Leaves of sweetpotato and a related species are human food in some countries and may be a major source of lutein for commercial purposes.

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I.L. Goldman

Pigments in orange carrot tissue, such alpha and beta carotene, are important vitamins in the human diet. Previously identified white or nonpigmented carrot roots, such as those from wild carrot and white derivatives of yellow or orange types, are dominant to the production of pigment, which is recessive. A nonpigmented carrot root was discovered during routine propagation of the inbred line W266 in 1992. Subsequent segregation analysis in the F2 and BC1 generations in three genetic backgrounds demonstrated the lack of pigmentation is due to a single recessive gene (reduced-pigment: rp). Total carotenoid content was reduced 92% in the roots of rprp genotypes compared to RPRP genotypes, however there were no differences in carotenoid content in leaves. Plants carrying rprp also exhibit white-speckled leaves during early stages of development, suggesting rp has an effect on leaf chlorophyll content. This character may prove useful in dissecting the complex inheritance of carotenoids in carrot.

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Gene E. Lester

Analyses of sensory attributes from 19 netted muskmelon (Cucumis melo L.) cultivars and breeding lines showed that flavor, (r= .92) had the highest significant correlation with overall fruit acceptance, while appearance (r = .72), color (r = .71) and internal color (r = .68) were secondary, and texture (r = .41) was not significantly correlated with overall fruit acceptance. Chemical attributes of soluble solids, fresh weight, dry weight, beta-carotene, firmness, fructose, glucose, sucrose, and total sugars shoved that total sugars per g fresh weight had the highest significant correlation (r = .68) with overall fruit acceptance. Total sugars per g fresh weight was significantly correlated with flavor (r = .65). Although, sugars were correlated with flavor, sugars when compared to flavor were less important in determination of overall muskmelon fruit preference.

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Leslie A. Weston and M.M. Barth

Vegetables provide a major source of essential vitamins such as ascorbic acid and beta carotene and other quality components in the human diet. Postharvest yield and quality of vegetables depend upon genetic, biotic, edaphic, chemic and other factors, as well as combinations of these factors. Successful production, quality and nutritional value of vegetables are related to both primary and secondary metabolic processes occurring during vegetable growth and development. Related research has focused upon cultivar selection, cultural practices used during production, interaction of light and temperature, and use of chemicals for growth regulation, and pest control. We will discuss the effects of genetic, pest, and soil management; crop maturity at harvest; environmental modification; and climatic conditions. Postharvest vegetable quality will be characterized in terms of vitamin content, appearance, yield, and flavor.

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Gene Lester

Within the Cucurbitaceae are two genera, Cucumis and Citrullus (muskmelons and watermelon, respectively), with sweet-tasting fruits. Per-capita consumption of these two genera rank melons (11.6 kg) second only to bananas (12.6 kg) as the most-consumed fruit in the United States. Consumption of melons, especially muskmelon and honey dew fruits, is significant from the standpoint of their nutritional benefits to humans. Orange-fleshed melons provide a person with 100% of their daily requirement of vitamins A and C. Melons also are a significant source of nutrients: sugars, dietary fiber, calcium, iron, potassium, and “phytochemicals.” Phytochemicals are compounds not presently recognized as having nutrient value. Thirty-eight known phytochemicals are in melons and have preventive properties in addition to anti-cancer attributes. Use of beta-carotene-rich melons is important in chemopreventive trials. Melon production and genetic factors may affect human health-beneficial nutrient and phytochemical quality attributes.

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Kil Sun Yoo*, Julio Loaiza, Kevin Crosby, Leonard Pike, and Steve King

About 40 watermelon samples with various flesh colors (red, pink, orange, and yellow) were tested for their carotene, sugar, and ascorbic acid contents. Carotenoids were separated and purified by using a preparative HPLC system and identified by comparing the spectra with standard compounds by using a diode array detector. Sugar and ascorbic acid contents were measured by HPLC methods. Red and pink colored watermelon contained lycopene as the major carotenoid, with a wide range of variation (5 to 51 μg·g-1). Beta-carotene was the second major carotenoid and was less than 6 μg·g-1. There were also lutein and violazanthin in less than 1.5 μg·g-1 range. Yellow and orange flesh watermelons contained a complex mixture of carotenes. Prolycopene, lycopene, or beta-carotene was the major component, depending on the variety, and the contents were less than 24, 3, and 9 μg·g-1, respectively. There were also minor carotenoids, such as violaxanthin, lutein, neurosporene, zea-carotene with a 0 to 3.5 μg·g-1 range. Neurosporene, zea-carotene, and prolycopene were not found in the red watermelons. There was great variation in total sugar content, range being from 22 to 102 mg-1, while the °Brix was from 4.0 to 15.5. Sucrose, glucose, and fructose were the main sugars in the watermelon and their composition were grouped as sucrose-dominant or fructose-dominant groups. Some varieties with very low levels of sucrose were generally low in the total sugar content. Watermelon contained fairly low levels of ascorbic acid, less than 58 μg·g-1 and some varieties had nearly no ascorbic acid. Estimation of total carotenoid in the yellow watermelons by measuring absorbency at 435, 485, or 503 nm was tested and 435 nm showed the highest correlation coefficient (r 2 =0.845).

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Khalid Ibrahim and John Juvik

Vegetables are a rich source of dietary carotenoids and tocopherols, powerful antioxidants that have the capacity to protect cells against oxidative damage caused by free radical reactions. There is evidence for a negative correlation between the incidence of certain types of cancer, age-related macular degeneration, cataract development, and cardiovascular disease with increased carotenoid and tocopherol intake. Development of elite vegetable germplasm with enhanced levels of these phytochemicals will potentially promote health among the consuming public. To assess the feasibility for genetic improvement in phytochemical content, it is necessary to partition the phenotypic variability into its component sources (genotype, environment, and genotype by environment interaction). To provide data for comparison and partition of phenotypic variation, 41 sweet corn and 13 broccoli genotypes were grown and harvested in one location for 3 years and analyzed for phytochemical content by HPLC. The most abundant form of carotenoids and tocopherols were lutein and gamma-tocopherol in sweet corn and beta-carotene and alpha-tocopherol in broccoli. Analysis of variance showed that, in sweet corn, the differences among genotypes described most of the phenotypic variation (76% for lutein, and 78% for gamma-tocopherol). Genotype by year interaction was a second significant factor, while variation affiliated with the year was found to be a minor component. In contrast, in broccoli, the three sources of variability contributed equally to describe the total phenotypic variation for beta-carotene and alpha-tocopherol. These results suggest that elite sweet corn and broccoli germplasm with improved carotenoid and tocopherol levels can be developed using conventional breeding protocols.

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Khalid E. Ibrahim, Kanta Kobira, and John A. Juvik

Genotype-by-environment interaction (G×E) is a fundamental concern in plant breeding since it hinders developing genotypes with wide geographical usefulness. Analysis of variance (ANOVA) has been widely used to interpret G×E, but it does not elucidate the nature and causes of the interaction. Stability analysis provides a summary of the response patterns of genotypes to different growing environments. Two classes of phytochemicals with putative health promoting activity are carotenoids and tocopherols that are relatively abundant in broccoli. Growing clinical and epidemiological evidence suggests that vegetables with enhanced levels of these phytochemicals can reduce the risk of cancer, cardiovascular, and eye diseases. The objective of this study is to have better understanding of the genetic, environmental and G×E interaction effects of these phytochemicals in broccoli to determine the feasibility of the genetic enhancement. The ANOVA and Shukla's stability test were applied to a set of data generated by the HPLC analysis of different carotenoid and tocopherol forms for six broccoli accessions grown over three environments. The ANOVA results show a significant G×E for both phytochemicals that ranged from 22.6% of the total phenotypic variation for beta-carotene to 54.0% for delta-tocopherol while the environmental effects were nonsignificant. The genotypic effects ranged from as low as 1% for alpha-tocopherol to 31.5% and 36.0% for beta-carotene and gamma-tocopherol, respectively. Stability analysis illustrated that the most stable genotype for all phytochemicals is Brigadier. The results suggest that feasibility of the genetic enhancement for major carotenoids and tocopherols. A second experiment that includes a larger set of genotypes and environments was conducted to confirm the results of this study.