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Jennifer L. Baeten, Thomas C. Koch and Irwin L. Goldman

Carrot has been bred for increased levels of pro-vitamin E α-tocopherol. This vitamin is lipid soluble. Carrot root has been shown to have measurable levels of lipid, but it is not certain if the lipid level is correlated to α-tocopherol levels. The HPLC method is needed to quantify levels of α-tocopherol. Measuring lipids may be less time consuming in a breeding program. We developed a method for extracting lipids from carrot tissue based on the Soxhlet extraction method. The Soxhlet extraction uses a non-polar ether solvent to pull lipids out of freeze-dried tissue. A collection of carrot accessions ranging in α-tocopherol concentration 0.04–0.18 ppm and carotenoid concentration 10.63–1673.76 ppm were used in this investigation. Root tissue was freeze-dried and lipid levels were measured in an experiment with two replications. The mean lipid level of root tissue was 0.05 g fat/g tissue. The range was 0–1.1 g fat/g tissue. Phenotypic correlations were performed among lipid, α-tocopherol, and β-carotene concentrations in these samples. Twenty-four samples were tested for lipid levels (12 high and 12 low). From these results, percent lipid of the root was determined. Correlations were made between the lipid data and α-tocopherol data of the given samples.

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James M. Bradeen and Philipp Simon

The Y2 locus conditions α- and β-carotene accumulation in the xylem (core) of carrot roots. The dominant allele suppresses carotene, but not xanthophyll accumulation, resulting in yellow-cored roots. Individuals homozygous for the recessive allele are rich in carotenes and are therefore orange-cored. Increased consumer interest in high carotene produce requires improved understanding of carotene biosynthesis and color development and more-efficient breeding techniques. We examined 103 F2 individuals generated from inbred populations differing in core carotene content. Bulked segregant analysis identified AFLP bands putatively linked to Y2. Linkage was confirmed for some bands by mapping. Linked bands were excised from gels, re-amplified, cloned into pGEM vectors, and sequenced. Cloned fragments and sequence information were used to characterize larger genomic regions to identify codominant markers. Currently we are developing codominant, PCR-based markers that can be used to rapidly genotype individuals in breeding programs, to characterize wild, feral, and cultivated populations for diversity and evolution studies, and to examine the role of Y2 in carotene accumulation.

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Penelope Perkins-Veazie, Julie Collins, Richard Hassell, Steve Olson, Donald Maynard, Jonathan Schultheis, Missy O'Hern, Toni Magby and Shelli Magby

Mini watermelons are the size of cantaloupes and weigh 1.5 to 3 kg (4 to 8 lbs). Melons of 18 selections were grown in replicated trials in North Carolina, South Carolina, and north and south Florida. Melons were harvested when ripe, and samples of heart and locule tissue were frozen and sent to Lane, Okla. A total of 960 samples, representing 6-12 melons per selection per location, were analyzed for total lycopene content using colorimeter and spectrophotometer methods. Subsamples of `Mohican', `Hazera 6007', `Vanessa', `Petite Treat', and `Precious Petite' were analyzed by HPLC for carotenoid profiles. Total lycopene content ranged from 52 to 108 μg·g-1, depending on variety. Selections were grouped into two levels of lycopene content. The varieties Precious Petite, Petite Perfection, Betsy, Bonny, Petite Treat, Valdoria, Vanessa, Hazera 5133 and 5138, RWT 8149, 8155, 8162 had 60 to 79 μg·g-1 lycopene and the varieties Hazera 6007, 5123, 5109, 5177, Mohican, and Extazy had 80 to 100 μg·g-1. Melons harvested from the Florida locations had more total lycopene than those from North and South Carolina. `Precious Petite' had more β-carotene as a percentage of total carotenoids than other varieties tested. These results indicate that lycopene content is affected primarily by germplasm and also by environment.

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Alexis M. Barbarin, Frank J. Williams, Greg T. Bettmann, Donald P. Hauber and Harish H. Ratnayaka

'Knowledge of constitutive levels of gas exchange and antioxidant properties under unstressed conditions is critical for elucidating their potential roles in stress tolerance, planning cultural practices, and evaluating nutritional quality of vegetable crops. This greenhouse study reports gas exchange, photosystem II efficiency, and pigment and antioxidant profiles of two spinach cultivars [SpinaciaoleraceaL., cvs. Bloomsdale Long Standing (Bloomsdale) and Hybrid Tyee (Tyee)] with contrasting morphology. `Bloomsdale', the cultivar with more compact stature and larger leaves, had 47% greater photosynthesis (P net) than `Tyee'. Stomatal conductance (g s) and transpiration (E) were 94% and 46% greater in `Bloomsdale' than `Tyee', respectively. However, photosystem II efficiency (F v'/F m') was only 8% greater in `Bloomsdale' than `Tyee'. Instantaneous water use efficiency was similar in both cultivars. `Bloomsdale' had nonsignificantly greater concentrations of chlorophylls a and b, lutein, β-carotene and violaxanthin than `Tyee'. Both cultivars had similar, marginal α-tocopherol concentrations (<0.1 ng·g-1 FW). However, `Tyee' had a greater chlorophyll a:b ratio which, combined with lower g s and E, suggests a possible advantage for `Tyee' over `Bloomsdale' under relatively dry and high light conditions. Further studies must be conducted to compare nutritional quality of the two cultivars, based on constitutive levels of pigments and antioxidants. Greater gas exchange activity in `Bloomsdale' than `Tyee' appears to be due more to CO2 acquisition/metabolism than photosystem II efficiency or concentrations of pigments and antioxidants.

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Yan Wang and Stanley J. Kays

Flavor quality is one of the most difficult traits to select in plant breeding programs due to the large number of sensory panelists required, the small number of samples that can be evaluated per day, and the subjectivity of the results. Using sweetpotato [Ipomoea batatas (L.) Lam.] as a model, clones exhibiting distinctly different flavors were analyzed for sugars, nonvolatile acids, and aroma chemistry to identify the critical flavor components. Differences in sugars, sucrose equivalents, nonvolatile acids, and 19 odor-active compounds were identified that accounted for differences in flavor among the clones. Using the intensity of the aroma per microliter for each of the 17 most important aroma-active compounds (maltol, 5-methyl-2-furfural, 2-acetyl furan, 3-furaldehyde, 2-furmethanol, benzaldehyde, phenylacetaldehyde, β-ionone, 1,2,4-trimethyl benzene, 2-pentyl furan, 2,4-decadienal, 2,4-nonadienal, linalool, geraniol, cyperene, α-copane and a sesquiterpene) and the relative sweetness of individual sugars × their respective concentrations, multivariate (principal component and cluster) analysis allowed accurate classification of the clones according to flavor type without sensory analysis. The level of precision was such that sweetness, starch hydrolysis potential, and the concentration of β-carotene could be accurately predicted by quantifying specific volatiles. Analytical assessment of flavor would greatly facilitate the accurate evaluation of large numbers of progeny, the simultaneous selection of multiple flavor types, and the development of superior new cultivars for a wide cross-section of food crops.

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Rachel A. Itle and Eileen A. Kabelka

/WHO, 2002 ; Murkovic and Neunteufl, 2002 ). In vegetables, common provitamin A carotenoids include β-carotene, α-carotene, and β-cryptoxanthin ( ODS/NIH, 2006 ). Other common carotenoids such as lycopene, lutein, and zeaxanthin do not have vitamin A

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Haejeen Bang*, Sungil Kim, Daniel Leskovar and Stephen King

Carotenoids are plant compounds that serve a variety of essential functions in the plant and have also been found to have several health-promoting activities in humans. Carotenoids found in watermelon (Citrullus lanatus) flesh are responsible for the various colors such as red, yellow and orange. Previous inheritance studies of flesh color revealed that six genes were involved in color determination. The relationship and interaction of these genes suggests that some color-determining genes may be the result of mutations on the structural genes encoding enzymes in the carotenoid biosynthesis pathway. In this study we were able to isolate and sequence six genes encoding enzymes involved in the carotenoid biosynthetic pathway, and determine their expression in different colored watermelon fruit. The cDNA was synthesized from total RNA using RACE (Rapid Amplification of cDNA ends) kit (SMART RACE cDNA Amplification Kit; Clontech, Palo Alto, Calif.). Degenerate primers were designed based on published homologous genes from other species and were used to isolate gene fragments and full-length cDNAs of phytoene synthase, phytoene desaturase, _-carotene desaturase, β-cyclase, β-carotene hydroxylase and zeaxanthin expoxidase. RT-PCR was carried out to examine any differential expression of cloned genes in white, yellow, orange and red-fleshed watermelon. All cloned enzyme-encoding genes were expressed regardless of flesh colors. These results indicate that carotenoid biosynthesis may be regulated at the post-transcriptional level. One interesting feature supports this hypothesis. In case of β-cyclase, a 229-bp leader intron was identified, and an unspliced mRNA with this leader intron existed dominantly in cDNA pool of all samples.

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James Mattheis and David Rudell

Metabolism of peel constituents was assessed during ripening of `Delicious' and `Golden Delicious' apples. The ethylene action inhibitor 1-methylcyclopropene (1-MCP) and/or controlled atmosphere storage (CA) were used to limit ethylene activity during and after storage at 1 °C. `Delicious' apples not exposed to 1-MCP developed a brownish discoloration (not superficial scald) during the initial 2 months of storage in air. LC/MS analyses of peel components indicated 1-MCP and/or CA inhibited the degradation of compounds responsible for red peel color (i.e., idaein) as well as other flavonoids. Ethylene regulation of metabolism of other phenolic and related constituents including (-)epicatechin and chlorogenic acid appears to be compound specific. The (-)epicatechin content is not impacted by 1-MCP or CA, while chlorogenic acid accumulation is reduced in fruit exposed to 1-MCP and/or stored in CA. β-carotene and lutein content in peel of `Delicious' fruit stored in air was lower compared with untreated controls. Chlorophyll degradation was enhanced in air-stored fruit previously exposed to 1-MCP; however, this result was not observed in 1-MCP exposed fruit from CA. Results for `Golden Delicious' apples also indicated that exposure to 1-MCP and CA, as well as storage duration, impacts metabolism of peel constituents. Chlorophyll degradation was delayed in fruit previously exposed to 1-MCP and then stored in CA. Impacts of 1-MCP and storage environment on concentrations of other `Golden Delicious' peel constituents increased with storage duration. The results indicate metabolism of apple fruit peel constituents during fruit ripening is differentially regulated by ethylene.

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Desmond Mortley, Jill Hill, Conrad Bonsi, Walter Hill and Carlton Morris

Tuskegee University is conducting research on salad crops as part of the National Aeronautics and Space Administration's (NASA) goal of supporting humans on near-term space missions, such as on the International Space Station. Small areas of salad crops are ideal candidates for growing in limited volumes, and would provide a source of fresh food to enhance the crew's nutrition. Baseline controlled environment studies were initiated to evaluate the response of eight carrot cultivars (`Baby Mini', `Nantes Touchan', `Danvers 126', `Kundulus', `Nanco Hybrid', `Thumbelina', `Early Nantes', and `Juwarot') to growth and yield in hydroponics. Seeds were sown in moist arcillite and transplanted into growth troughs (0.15 × 0.15 × 1.2 m) after 18 days in reach-in growth chambers, and nutrients continuously supplied by a half-Hoagland solution. Growth chambers conditions included 300 μmol·m-2·s-1 photosynthetic photon flux, 16/8 photoperiod, a constant 25 °C and relative humidity of 50%. Plants were harvested at about 80 days. All eight cultivars grew well in the hydroponic system. Seven cultivars produced greater shoot fresh than root mass except `Baby Mini', which showed the reverse. `Danvers 126', followed by `Nanco Hybrid' and `Nantes Touchan', produced highest root yields. The β-carotene content varied by cultivars. The highest level of 10,400 IU/100 g was obtained for `Thumbelina', followed by `Baby Mini' (8040 IU/100 g), `Juwarot' (6160 IU/100g), and `Early Nantes' (5210 IU/100 g), and the lowest by `Nantes Touchan' (3510 IU/100 g). These results show that while carrots adapted well to growth in hydroponics, carotene, a major nutrient, was at relatively low levels.

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Neda Keyhaninejad, Richard D. Richins and Mary A. O’Connell

; these pigments are important for attracting pollinators and seed dispensers. In humans and other animals, specific carotenoids provide essential vitamin precursors; β-carotene and β-cryptoxanthin are pro-vitamin A forms of carotenoids ( Yeum and Russell