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Abstract

It is a pleasure to be introducing this symposium to provide an appreciation of the real interest that NASA has in using plant systems for life support in space. The symposium is directed toward providing details on what is planned, and what is actually underway, in this effort. It is a program that has been titled CELSS, Controlled Ecological Life Support System, and involves a tremendous breadth of horticultural areas—areas that can require the expertise of nearly everyone in horticulture, as suggested in Fig. 1. The project must start with plant propagation, probably tissue culture propagation, and involve all aspects of environmental optimization of growth, breeding of adapted cultivars, nutrient, possibly nutrient film, feeding techniques (NFT) and automated nutrient recycling, contaminant control in the atmosphere, pathogen control in the nutrient solution, precise growth modeling for regulation of the system, maximization of harvest index to reduce inedible portions, efficient food processing, balanced diets, and complete recycling of all wastes. The expertise of all types of horticulturists is needeed if this project of NASA is to be successful.

Abstract

People unaware of the great differences among horticultural crops often regard fruits and vegetables each as a homogeneous group when considering requirements for implementation and support of breeding programs. Each fruit and vegetable crop is different enough, and of sufficient importance, to merit individual consideration. Although the total dollar value or hectarage grown are measures of economic worth of a crop, other factors must be considered when determining the importance of horticultural crops either singularly or as a group. Generally horticultural crops require more intensive culture than field crops, and thus are grown with greater risk which is rewarded by a higher per acre value. The contributions of the horticultural crops to our daily diets are far greater than economic values indicate. The USD A task group (Senti Committee) on GRAS status of new plant cultivars pointed out that fruits and vegetables provide 90% of the Vitamin C, 50% of the Vitamin A, 30% of the B6, 25% of the magnesium, 20% of the thiamin, and 18% of the riboflavin and niacin in the United States food supply. Research support for horticultural crops must reflect, in part, their dietary importance rather than solely their dollar value.

Abstract

Starch granules were extracted from maize (Zea mays L.) endosperm of mature F₂ kernels of IA5125 × IA453 normal, amylose-extender (ae), dull (du) waxy (wx), and ae du wx and from ae du wx F₂ kernels harvested at the fresh market stage of development. Samples were digested for 1.5 hours with hog pancreatic α- amylase and Rhizopus II amyloglucosidase. The mature and immature ae du wx samples were usually digested significantly more than the other 4 genotypes, while ae was digested significantly less than the others. Digestion of starch granules from mature and immature ae du wx kernels did not differ. The sweet corn background used had little effect, since our observations of the single mutant genotypes were similar to those in a dent background. Clearly, ae du wx starch granules do not reflect the reduced digestibility associated with ae, and thus cultivars homozygous for ae du wx are not inferior with respect to their ability to supply carbohydrates to the diet.

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.

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.

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.

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.

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.

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.

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.