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Roseann Leiner, Abraham Smyth, Rudy Candler, and Patricia S. Holloway*

Berries and vegetables can be sources of beneficial phytochemicals that may have antioxidant activity in the human diet. Information on type and quantity of phytochemicals may open new crop opportunities for berries and vegetables harvested in Alaska. A method was developed for detecting ascorbic acid and eight phenolic acids on an HPLC instrument using a reverse phase Merck Chromolith C18 column. The method used UV absorbance detection at 280nm to separate a standard solution of the following nine phytochemicals: ascorbic acid, gallic acid, protocatechuic acid, p-hydroxybenzoic acid, p-hydroxyphenylacetic acid, caffeic acid, syringic acid, p-coumaric acid and ferulic acid. The mobile phase was a mixture (3.5% to 14% gradient) of organic solvent (5 parts acetonitrile: 2 parts methanol) and aqueous solvent (2 mmol aqueous trifluoroacetic acid - TFA) at a flow rate of 2 mL/min. In 2003, over 60 samples of berries and 60 samples of baby greens were extracted and analyzed. Plant samples were extracted by blending 10-20g of frozen plant tissue with 5 parts TFA. The extracts were centrifuged, diluted 4:1 and filtered (0.2 μm). Chromatograms from HPLC analysis for all samples were complex in peak size and number. Chromatograms for six extracts of high bush cranberries, Viburnum edule, exhibited intense peaks that indicate the presence of caffeic acid, based on retention times. Chromatograms for seven extracts of rose hips, Rosa acicularis, exhibited peaks that indicate the presence of ascorbic acid, based on retention times. Gallic acid and p-hydroxybenzoic acid are apparent minor components in the leaves of some baby greens. This research will continue in 2004 with more plant samples and further method development for detection of other phytochemicals.

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Allison E. Stewart, Debra J. Carpenter, Vincent R. Pantalone, and Carl E. Sams

Consumer interest in Edamame (edible soybean) is increasing due to reported health benefits associated with diets high in soy. The purpose of this study was to compare four varieties of edible soybean grown at four plant spacings on three planting dates. The lines were grown at the Plateau Research and Education Center in Crossville, Tenn. They were analyzed for horticultural traits and isoflavone content. All lines were at the R6 stage. Fresh weight of pods, weight of 200 pods per plot, the number of seeds per 200 pods, and the weight of 100 seeds were recorded from two-row plots (6.10 m x 1.52 m). A significant (P < 0.001) difference was found for fresh weight among planting dates. The May planting had the highest mean fresh weight (3118 g/plot), followed by the June (3068 g/plot) and July (2131 g/plot) dates. The weight per 100 seeds was significantly different (P < 0.001) for planting date and genotype. May seed weight was highest at 49 g, followed by June at 45 g, and July at 42 g per 100 seeds. `Gardensoy-43' was the highest-yielding variety, with a mean of 3253 g/plot. It was followed by `TN00-60' and `TN03-349', with mean fresh weights of 2730 and 2723 g/plot, respectively. The line `TN5601T' had the lowest mean fresh weight of 2389 g/plot. Both fresh weight (P < 0.001) and weight per 100 seeds (P < 0.05) were significantly different among plant spacings. Twenty-six plants per meter within rows yielded the highest total fresh weight per plot (3071 g), but had the lowest mean weight per 100 seeds (43 g). Spacing three plants per meter within rows resulted in the highest weight per 100 seeds (48 g), but the lowest fresh weight per plot (2122 g). Isoflavone content will be measured for each variety, planting date, and spacing.

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X.E. Yang, X.X. Long, W.Z. Ni, and E.W. Stover

Vegetables play an important role in the human diet, and production in suburban areas has increased as populations have become more urbanized. However, heavy metal pollution of soils has enhanced in such areas, and metal accumulation in vegetables may pose a human health risk when consumed. Zinc is an essential micronutrient for plants and humans, but it is toxic to plants and humans at high levels. Although a maximum Zn tolerance for human health has been established for edible parts of vegetables (20 mg/kg DW), little information is available for predicting vegetable Zn concentration based on soil and water Zn levels. The objectives of this study were to determine the critical Zn concentrations in nutrition solution and soil to reach maximum Zn tolerance concentrations in Chinese cabbage, bok choy, and celery. Five Zn levels were used for both solution and soil culture experiments, with three replicates of each. Shoot growth was significantly inhibited at Zn concentrations above 50 mg/L in nutrition solution and above 180 mg/kg in soil. The sensitivity of crops to zinc toxicity, in term of shoot and root growth, decreased in the order: celery > Chinese cabbage > bok choy. Zinc accumulation in shoots and edible parts varied with Zn supply levels and type of vegetables. A negative correlation was noted between Zn accumulation and dry matter yields, with r-squared values of 0.980** for nutrient solution and 0.960* for soil culture. Zinc concentrations in shoots or edible vegetable parts were below 20 mg/kg (human health threshold) when they were grown at DTPA extractable Zn in the soil less than 75, 100, and 175 mg/kg for bok choy, celery, and Chinese cabbage, respectively.

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Geoffrey Meru and Cecilia McGregor

Egusi watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai subsp. mucosospermus var. egusi (C. Jeffrey) Mansf.] is known for its distinctive fleshy-pericarp seed phenotype and high seed oil percentage (SOP). The seed is part of the daily diet in West Africa where it is used in soups and stews or processed for cooking oil. Genetic mapping studies have revealed that most of the variation in SOP between egusi and normal, non-egusi seed is explained by the egusi (eg) locus, which is also associated with the unique seed phenotype. However, variation in SOP is also observed within egusi and normal seed types although the basis of this variation remains to be elucidated. A high correlation between kernel percentage (KP) and SOP has been observed in watermelon and other crops, and recent data also suggest an association between seed size and SOP in watermelon. The aim of this study was to elucidate the relationship among SOP, KP, and seed size traits in watermelon and to identify quantitative trait loci (QTL) associated with the latter traits to facilitate marker-assisted selection (MAS) for traits correlated with SOP. KP showed a significant (α = 0.05) positive correlation with SOP in both egusi and normal seed types, whereas seed size traits showed significant negative correlations with SOP. QTL associated with KP and seed size traits in normal seed were colocalized with a previously mapped locus for SOP on linkage group (LG) 2, but in egusi seed, a QTL explaining 33% of phenotypic variation in KP was localized on LG 7. The results of this study show that SOP in watermelon is correlated with KP and seed size, but KP is associated with different loci in normal and egusi seed phenotypes.

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Francisco Radillo-Juárez*, Marcelino Bazán-Tene, Jaime Molina-Ochoa, and Edgar Damián Rolón-Vejar

The production of `Jalapeño' hot pepper has been increased in the last 10 years in about 6.21% during the period between 1992-2003, with a growing rate of 72%. In Mexico, is an important produce, because it is considered part of the traditional Mexican diet as well as its high productive level. One of the most frequent problems in this crop is the low production of fresh fruits caused by an inadequate fertilization. The objective of this research was to evaluate the effect of four fertilization formulas on the yield of fresh fruit of hot pepper variety Jalapeño cultivar Grande under irrigation conditions The evaluated formulas were (N-P-K-S): 1) 58-51-35-12 (control); 2) 78-68-46-16; 3) 97-85-58-20; and 4) 117-102-69-24. Treatments were distributed under a completely randomized block design with four replications. The formula 117-102-69-24 showed the highest values in the plant height and number of fruits with 62.5 cm, and 48 fruits, respectively. This formula also showed the highest values on equatorial and longitudinal diameters, and fruit weight with 3.36 cm, 11.26 cm, and 33.66 g, respectively. The total yields per plant and per hectare was 1.54 kg; and 38.22 t was obtained with the formula 117-102-69-24. The formula with the higher units of each element showed the best performance and exhibited the highest yield of fresh hot pepper, it was more productive than the control treatment commonly used by the hot pepper growers in Colima.

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Chieri Kubota, Cynthia A. Thomson, Min Wu, and Jamal Javanmardi

Plants produce various phytochemicals that are of nutritional and medicinal value to humans. Phytochemicals having antioxidant capacity are drawing increased interest from consumers. Population studies among Americans have consistently demonstrated inadequate consumption of fruit and vegetables. Improving intake of fruit and vegetables has been a major public health effort for many years with minimal success. Given this, it seems opportunistic to consider other approaches to enhance the nutritional quality of the American diet. One plausible approach is the development of fresh produce containing a greater concentration of phytochemicals known to improve health, thus while consuming fewer servings of produce, Americans would still have significant exposure to health-promoting food constituents. Controlled environments provide a unique opportunity to modify the concentrations of selected phytochemicals in fruit and vegetables, yet practical information is limited regarding methods effective in optimizing antioxidant capacity. Our research at the University of Arizona Controlled Environment Agriculture Program has shown that application of moderate salt stress to tomato plants can enhance lycopene and potentially other antioxidant concentrations in fruit. The increase in lycopene in response to salt stress in the tomato fruit was shown to be cultivar specific, varying from 34% to 85%. Although the specific biological mechanisms involved in increasing fruit lycopene deposition has not been clearly elucidated, evidence suggests that increasing antioxidant concentrations is a primary physiological response of the plant to the salt stress. Another experiment showed that low temperature during postharvest increased antioxidant capacity of tomato fruit while it maintained the lycopene concentration. More detailed study in this area is needed including accumulation of antioxidant phytochemicals as affected by environmental conditions during the cultivation and the postharvest.

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Alexandra B. Napier, Kevin M. Crosby, and Soon O. Park

Muskmelons (Cucumis melo L.) play an important role in the American diet. Ranked as one of the top 10 most-consumed fruits by the USDA, cantaloupe melons have the highest amount of beta-carotene of all the ranked fruits. Beta-carotene, also called pro-Vitamin A, is an essential nutrient required for eye health, and may have the potential, as an antioxidant to reduce the risks associated with cancer, heart disease, and other illnesses. Breeding melons with increased levels of beta-carotene will benefit consumer health. Research has found phytonutrients are most bioavailable when consumed in their fresh form, rather than as vitamin supplements. The high level of beta-carotene found in some melons has a genotypic component, which may be exploited to breed melons high in beta-carotene. Molecular markers and marker-assisted selection (MAS) can be used to increase the efficacy of the breeding process, while lowering breeding costs. An F2 population was created using `Sunrise', the female parent, containing no beta-carotene crossed with `TAM Uvalde', a high beta-carotene variety. A field population consisting of 115 F2 individuals and a greenhouse population containing 90 F2 individuals were grown. The resulting fruit were screened phenotypically and ranked according to beta-carotene content. Chisquare values fit the previously reported model of a single dominant gene for presence of beta-carotene (orange-flesh) vs. absence (green or white flesh). A continuous distribution of beta-carotene concentrations from high to low suggested quantitative inheritance for this trait. Two eight-plant DNA bulks composed of either high or low beta-carotene F2 individuals were screened for polymorphic molecular markers using the amplified fragment-length polymorphism technique.

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Everardo Zamora, Santiago Ayala, Cosme Guerrero, Damian Martínez, and Francisco Rivas

The pod cactus (Opuntia sp.), a tender stem, has been consumed by Mexican people for centuries either as a fresh or boiled vegetable. Traditionally, Southern Mexico people consume this tender pod cactus in several traditional Mexican dishes. During recent years, an increase in nopalitos consumption by Sonoran people has been observed. People interested in a disciplined diet or people troubled with high cholesterol desire this peculiar vegetable. In Hermosillo, Mexico, people buy nopalitos in small plastic bags packages a pound of small cutting of tender pods from local supermarkets and mobile sellers. Usually, a nopalitos bag pound price is a range of $1.00 to $1.2 U.S. dollars in Hermosillo. Nopalitos production in Sonora, Mexico, is a seasonal. Nopalitos harvesting starts in early April and runs through late October. Because low temperatures start in late October, and continue during the winter season, there is no nopalitos production in Sonora. Hense, Sonoran producers are considerig building high tunnels, to provide more temperature control and to produce nopalitos during the winter. Most growers are low-income people that produce nopalitos in home gardens. This activity allows low-income growers to have nopalitos during most of the year, except during the winter. The current growing area production of 240 acres (170 ha) of tender pod cactus was recorded during 2005 in Sonora, of which a half is cultivated in home gardens. A potential yield production of nopalitos in Sonora is about of 40 tons per acre of tender pod cactus. In comparison to other crops, nopalitos production is a good alternative for small growers.

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Usha Rani Palaniswamy, Richard McAvoy, and Bernard Bible

Omega-3 fatty acids (O3FA) are essential for normal human growth, development, and disease prevention. Purslane (Portulaca oleraceae L.) is an excellent source of the O3FA α-linolenic acid (LNA)—with higher concentrations than any green leafy-vegetable examined to date—and is being considered for cultivation (by USDA-ARS) in an effort to improve the balance of essential fatty acids in the western diet. Twenty-fi ve-day-old seedlings of both a green-leafed and a golden-leafed type of purslane were transplanted into a closed hydroponic system. Nitrogen, at 200 ppm, was provided as NO3 and NH4 forms to yield NO3: NH4 ratios of 1:0, 0.25:0.75, 0.5:0.5, and 0.75:0.25. Treatments were arranged in a randomized complete-block design with five replications. The experiment was repeated. Young, fully expanded leaves were harvested 18 days after treatment initiation, frozen (–60°C), and then analyzed for fatty acids using gas chromatography. Although the two types of purslane did not differ in LNA concentration, the green-leafed purslane produced greater total dry mass than the golden-type. On a leaf dry mass basis, plants grown with a NO3:NH4 ratio of 0.5:0.5 produced 241% and 53% greater LNA than plants grown with NO3:NH4 ratios of 1:0 and 0.75:0.25, respectively. Plants grown with NO3:NH4 ratios of 1:0 and 0.25:0.75 produced similar leaf LNA concentrations. Total dry mass was not affected by the nitrogen treatments.

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Kirk D. Larson

Replant soil fumigation with mixtures of methyl bromide (MeBr) and chloropicrin (trichloronitromethane) is a standard practice for pest and disease control in fruit crop nurseries in California. The proposed phase-out of MeBr by the year 2001 requires that alternative soil sterilants be studied for nursery use. Therefore, on 5 April, 1993, three preplant soil treatments were applied to new strawberry ground: 1) MeBr/chloropicrin (67:33) at 392 kg/ha: 2) chloropicrin, a possible MeBr substitute. at 140 kg/ha: and 3) nonfumigation. The experimental design was a RCB: there were two plots (each 10′ × 15′) for each of two cultivars (`Chandler' and `Selva') for the 3 soil treatments in each of 3 blocks. Mother plants were planted 26 April, and plots were machine-harvested in October, 1993. All plants from each plot were uniformly graded, after which mean stolon yield per mother plant, mean crown diameters, and crown and root dry wts were determined. Cultivar effects and cultivar × treatment interactions were not observed, so data for the two cultivars were pooled. Stolon production per mother plant was greatest for trt 1 (18.56 stolons), intermediate for trt 2 (15.75 stolons), and least form 3 (7.89 stolons). For trt 3, crown dieters. and crown and root dry wts were reduced relative to those of trts 1 or 2. Stolons from all trts were planted in a fruit production field on 13 October, 1993. After two months, canopy diameters were greatest for plants from trt 1 (27.1 cm), intermediate for plants from trt 2 (26.2 cm) and least for plants from trt 3 (24.9 cm). The results indicate that, compared to standard soil fumigation with MeBr/chloropicrin. small, but significant, reductions in runner production and plant vigor can be expected following nursery soil fumigation with intermediate rates of chloropicrin.