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Thomas S.C. Li and G. Mazza

Four-year-old American ginseng (Panax quinquefolium L.) plants and soil samples were collected from nine ginseng gardens. Soil and leaf mineral contents were determined and six major ginsenosides, Rb1, Rb2, Rc, Rd, Re, and Rg1, were extracted from leaves and roots and quantified by high-performance liquid chromatography (HPLC). Correlation coefficients were more significant for soil nutrient levels vs. ginsenoside contents of leaves than of roots, suggesting that soil nutrient levels may play a major role in the synthesis of leaf ginsenosides. Minor elements in the leaf were also better correlated with ginsenoside contents of the root than that of the leaf. Iron content in the leaves exhibited highly significant correlations with the levels of Rb1, Rb2, Rc, and Rd, but calcium and copper contents were negatively correlated with Rg1 in the roots.

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E.A. Baldwin, J.W. Scott, T.M. Malundo, and R.L. Shewfelt

Sugars, acids, and flavor volatiles are components of flavor that have been measured instrumentally, revealing differences among tomato cultigens. For objective measurements to be useful, however, they need to relate to sensory data. In this study, objective and sensory analyses of tomato flavor were compared. Seven tomato cultigens were ranked for sweetness, sourness, and flavor and rated for overall acceptability by a panel of 32 experienced judges. Sucrose equivalents (SE), measured by HPLC, but not soluble solids correlated with sweetness at P = 0.10. In addition, SE highly correlated with flavor (P = 0.03), while titratable acidity (TA) negatively correlated with overall acceptability (P = 0.03). Regression analysis indicated that 2+3-methylbutanol, cis-3-hexenal, and 6-methyl-5-hepten-2-one significantly contributed to flavor at a 5% level of significance. It is apparent from this study that sucrose equivalents are more meaningful than soluble solids for measurement of sweetness, and that certain flavor volatiles play a role in tomato flavor.

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Robert K. Stevenson and Karen K. Tanino

Dogwood (Cornus sericea L.) clonal ecotypes from northern latitudes (Northwest Territories “NWT”) and more southern latitudes (Massachusetts, Utah, and Chalk River, Ont.) were allowed to acclimate naturally in a shade house (52°07') beginning in early July and continuing through the middle of October. The NWT ecotype began to attain vegetative maturity by the second week of September, whereas the southern ecotypes did not attain any significant degree of VM before the first lethal frost.

Defoliation tests in controlled environment chambers paralleled shade house results. Under VM-inducing conditions (20/15°C, 8h), NWT ecotype attained VM after 40-50 days. Conversely, after 80 days Utah ecotype had not attained full VM.

Chilling requirement will be compared among ecotypes and ABA levels will be quantified using HPLC and ELISA systems. The results will be compared with date of VM attainment, subsequent freezing tolerance and satisfaction of the chilling requirement.

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Durel J. Romaine and Don R. LaBonte

Narrow-sense heritability (h2) estimates for sugars were determined to assess the feasibility of breeding for a sweeter baked sweetpotato. Roots of parents and half-sib progeny were baked (190°C for 75 minutes) 16 weeks after harvest. Sugars from 10 gram root samples were extracted in ethanol for HPLC sugar quantification. Alcohol insoluble solid (AIS) residues (starch) were also measured from the samples. Dry matter was determined on a separate 10-g sample. Narrow-sense heritability estimates based on variance components analysis for AIS and percent dry matter were 0.20 and 0.32, respectively. Estimates for sugar data were 0.05 for sucrose, 0.52 for maltose, and 0.52 for total sugars (fructose, glucose, sucrose and maltose). These heritability estimates for maltose and total sugars imply a breeder could expect a moderate gain in sweetness over several cycles of selection.

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Naoki Yamauchi, Xiao-Ming Xia, and Fumio Hashinaga

Effects of flavonoid pigments on chlorophyll (Chl) degradation by Chl peroxidase in the flavedo of Wase satsuma mandarin (Citrus unshiu Marc. var. praecox Tanaka) fruits were studied. Chl was degraded when hydrogen peroxide was added in a reaction mixture containing Chl and a phosphate buffer extract from the flavedo. Chlorophyllide, which was formed by the action of chlorophyllase in the extract, was also degraded. The flavonoid contents decreased with the Chl degradation in the reaction mixture. Analysis of the flavonoid with HPLC showed that hesperidin and narirutin were contained in the flavedo as a major flavonoid, and that the former decreased significantly and the latter showed almost no change with the Chl degradation in the reaction mixture. In the ethylene-treated fruits, the hesperidin content in the flavedo also decreased with the degreening of stored fruits, suggesting that the flavonoid oxidation by Chl peroxidase could be involved in the Chl degradation.

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Jeanne A. Briggs, Mellissa B. Riley, and Ted Whitwell

The pesticides isoxaben, trifluralin, chlorpyrifos, and thiophanatemethyl were applied at recommended rates to a 4-ha growing bed at an operating container nursery. Runoff samples produced by overhead irrigation were collected from three waterways, 300 feet long × 6 feet wide. The waterways were a sodded hybrid bermudagrass, a plantation of common cattails (Typha latifolia), and a gravel–clay waterway used as a reference. A 2-ha area drained into the sodded waterway, which flowed into the cattails, and a 2-ha bed flowed into the reference waterway. Samples were collected throughout the duration of runoff on day of treatment and at 1, 2, 8, 15, and 22 days after treatment. Runoff volumes were recorded over time as measured at weirs. Analysis was by HPLC following solid-phase extraction. Only isoxaben was detected at 2 days after treatment. Initial concentrations of all pesticides were lower in the vegetated waterways than in the reference.

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Ricardo Campos and William B. Miller

The relationship between the activity of soluble acid invertase and metabolism of soluble carbohydrates was investigated in snapdragon flowers. Flowers were harvested at three different developmental stages, and at four different dates. Soluble carbohydrates were extracted and analyzed by HPLC; invertase activity was determined in crude enzyme extracts. Sucrose concentration slowly increased throughout flower development from a closed bud to a fully open flower. Fructose and glucose concentration were relatively lower at the bud stage, increased during petal elongation, then slightly decreased at flower maturity. Mannitol concentration showed little change during flower development. An unknown compound increased in concentration during petal elongation and decreased at maturity. For all harvest dates, the specific activity of acid invertase increased with flower development. These results show a positive correlation of invertase activity and hexose sugars accumulation. It is possible that at maturity sugars are metabolized at a faster rate than produced, causing a slight decline in hexose sugars.

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H. Brent Pemberton, Yin-Tung Wang, Garry V. McDonald, Anil P. Ranwala, and William B. Miller

Case-cooled bulbs of Lilium longiflorum `Nellie White' were forced to flowering. When the tepals on the first primary flower bud split, plants were placed at 2 °C in the dark for 0, 4, or 21 days. After storage, plants were placed in a postharvest evaluation room with constant 21 °C and 18 μmol·m-2·-1 cool-white fluorescent light. Lower leaves, upper leaves, and tepals of the first primary flower from a concurrent set of plants were harvested for carbohydrate analysis using HPLC. Storage time did not affect carbohydrate levels in the lower leaf or tepal samples, but sucrose and starch levels decreased while glucose and fructose levels increased in the upper leaf tissue with increasing storage time. These changes were correlated with a decrease in postharvest longevity for the first four primary flowers. Longevity of the fifth primary flower and total postharvest life of the five primary flowers was unaffected by storage.

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Michael Cavalier, Armen Kachatryan, Evodokia Menelaou, Jack Losso, and Don LaBonte

Fresh leaves of six sweetpotato [Ipomoea batatas (L.) Lam.] genotypes, `Beauregard', `Bienville', L 99-35, L 00-8, L 01-145, and L 01-29 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 HPLC chromatograms, and, when spiked in pure lutein extract, did not interfere with lutein separation. 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 used as human food in some countries and could be a source of extracted lutein for commercial purposes.

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Naoki Yamauchi and Alley E. Watada

Degradation of chlorophyll in spinach (Spinacia olearacea L. cv. Hybrid 612) appeared to be regulated through the peroxidase-hydrogen peroxide pathway, which opens the porphyrin ring, thus resulting in a colorless compound. This conclusion was arrived at from the analysis of chlorophylls (Chls) and their metabolizes by HPLC and of enzyme activities catalyzing the degradative reactions. Chls decreased at 25C but not at 1C. The chlorophyll oxidase pathway was not active, as noted by the lack of accumulation of a reaction product named Chl a-1. Lipid peroxidation increased with storage, but the products of the reaction. did not degrade chlorophyll, as noted by the lack of increase in Chl a-1. Chlorophyllase activity increased, but chlorophyllide, the expected product of the reaction, changed minimally during senescence. Ethylene at 10 ppm did not alter the pathway that degraded chlorophyll in spinach.