Lettuce (Lactuca sativa L.) is an essential salad crop in the American diet. Nitrogen (N), phosphorus (P), and potassium (K) are required for successful lettuce production and can influence lettuce quality. The objective of the study was to evaluate changes in nutritional composition of romaine (`Green Tower') and iceberg (`Sharp Shooter') lettuce in responses to N, P and K fertilization during fall production in Salinas, Calif. Sixteen treatment combinations of fertilizer were selected to provide a range of treatments. N was applied at 0, 112, 225, and 338 kg·ha-1 as ammonium nitrate; P was applied at 0, 112, and 225 kg/ha as super phosphate; and K was applied at 0 and 112 kg·ha-1 as muriate of potash. Nutritional content of fresh tissue of two types of lettuce was analyzed using high performance liquid chromatography (HPLC). Among the parameters analyzed were lutein, beta-carotene, chlorophyll a, and chlorophyll b. Yield was increased with increasing N fertilizer level, but was not affected by P or K application rates. The best post harvest quality, however, was at moderate P application rate. Increasing the N and P rates gradually increased glucose content in lettuce but decreased the shelf life. Significant differences between the two types of lettuce were found in chlorophyll, lutein and beta-carotene content. No significant correlations were found between soil fertilizer application levels and nutritional content of lettuce. However, the ratio of chlorophyll a and b were greater with the increase of fertilizer rate. Nutritional composition including vitamin C will be presented.
Murshidul Hoque*, Husein Ajwa, and Beiquan Mou
M. Jalaluddin and Md. Shahidul Islam*
Foods from plants can provide enough energy and essential nutrients for maintaining human health as well as for prevention of many serious diseases. Many exotic vegetables are known for their special nutritional and medicinal properties. Bitter Melon (Momordica charantia L.), an annual vegetable of Cucurbitaceae family, is found to be one of the important vegetables of special nutritional and medicinal qualities. Germplasm lines and land races of Bitter Melon were evaluated in 2000 and 2001 for their adaptability in Southeast Arkansas. Seven adaptable lines/varieties were tested in replicated field trials for productivity at the Univ. of Arkansas at Pine Bluff Agricultural Research Center in 2002 and 2003. Melons were harvested at their marketable stages beginning in June and ending in September for yield estimation. Nutritional qualities of Bitter Melons were examined by chemical analyses conducted at the Univ. of Arkansas, Fayetteville (UAF) Food Science Laboratory. Analyses for antioxidants and other compounds as well as cooking qualities are currently underway. Several recipes have been tasted for consumer acceptance. The popular belief of bitter melon to improve glucose tolerance in Type II diabetes and lower blood cholesterol are being investigated. It is still to be determined if the chemical constituents such as certain alkaloids and polypeptides found in bitter melons are effective individually or in combination.
Recent advances in molecular genetics and genomics technologies have had a significant impact on tomato research over the last decade and are likely to have considerable influence on the nature and outcome of research activities related to tomato in the future. Specific applications of genomics technologies in our laboratory include positional cloning of genes associated with fruit ripening and quality (rin and nor), localization of ripening-related genes on the molecular-marker map to assist candidate gene discovery related to fruit ripening and quality, and characterization of mutants influencing fruit quality and nutritional value with the goal of identifying candidate genes for said mutants and alternative molecular tools for modification of fruit quality and nutrition. Isolation of the rin and nor genes has been verified via complementation of corresponding mutant tomato plants via insertion of the appropriate CaMV35s-driven wild-type sense cDNA. Both the rin and nor genes have sequence characteristics suggestive of transcription factors. Preliminary evidence suggests the role of similar genes in the ripening of additional climacteric and non-climacteric fruit species. Additional efforts in the laboratory include molecular analyses of light signal transduction as related to 1) regulation of carotenoid and flavonoid accumulation, and 2) potential manipulation of corresponding pathways for modification of fruit quality and nutrient value.
Geoffrey Meru and Cecilia McGregor
Watermelon is an economically important crop of the Cucurbitaceae family, popular for its sweet edible flesh ( Robinson and Decker-Walters, 1997 ). However, the seeds of watermelon provide a significant source of nutrition and income in other parts
Leslie A. Weston and M.M. Barth
137 COLLOQUIUM 3 (Abstr. 012–017) Effect of Preharvest Factors on Postharvest Quality
Holly L. Scoggins
Little taxa-specific information is available regarding the nutrition needs of container-grown herbaceous perennials. The goal was to determine optimum fertilizer concentrations and corresponding substrate testing values for greenhouse production of 10 taxa. Astilbe chinensis (Maxim.) Franch. & Savat.`Purpurkerze', Campanula carpatica Jacq. `Deep Blue Clips', Coreopsis verticillata L.`Golden Gain', Gaura lindheimeri Engelm. & Gray, `Siskiyou Pink', Heucherasanguinea Engelm. `Mt St. Helens', Lamium maculatum L. `White Nancy', Penstemon ×hybridus Hort. `Sour Grapes', Perovskia atriplicifolia Benth. `Longin', Salvia nemerosa L. `Blue Hill', and Veronica × Hort. `Goodness Grows' were grown for 10 weeks with 15N–7P–14K at four rates (50, 150, 250, and 350 mg·L–1 N) of constant liquid feed. Substrate pH and soluble salts levels were measured weekly using the pour-through extraction method. In analysis of all taxa, most effects [quality, shoot dry weight, pH and electrical conductivity (EC)] varied by rate × taxa. Though higher levels of fertilizer produced the largest plants in some cases, satisfactory quality was also attained with a lower rate. Quality and pH were negatively correlated for a few genera but most showed no relationship. Results of this study indicate not all taxa tolerate increased fertilizer levels and that the herbaceous perennials studied could be grouped by nutritional needs. Furthermore, target ranges for EC can be developed based on dry mass and quality ratings.
Adel A. Kader
Biological factors involved in deterioration of fresh horticultural perishables include respiration rate; ethylene production and action; compositional changes associated with color, texture, flavor (taste and aroma), and nutritional quality; growth and development; transpiration; physiological breakdown; physical damage; and pathological breakdown. There are many opportunities to modify these inherent factors and to develop genotypes that have lower respiration and ethylene production rates, less sensitivity to ethylene, slower softening rate, improved flavor quality, enhanced nutritional quality (vitamins, minerals, dietary fiber, and phytonutrients including carotenoids and polyphenols), reduced browning potential, decreased susceptibility to chilling injury, and increased resistance to postharvest decay-causing pathogens. In some cases the goals may be contradictory, such as lowering phenolic content and activities of phenylalanine ammonialyase and/or polyphenoloxidase to reduce browning potential vs. increasing polyphenols as antioxidants with positive effects on human health. Another example is reducing ethylene production vs. increasing flavor volatiles production in fruits. Overall, priority should be given to attaining and maintaining good flavor and nutritional quality to meet consumer demands. Extension of postharvest life should be based on flavor and texture rather than appearance only. Introducing resistance to physiological disorders and/or decay-causing pathogens will reduce the use of postharvest fungicides and other chemicals by the produce industry. Changes in surface structure of some commodities can help in reducing microbial contamination, which is a very important safety factor. It is not likely that biotechnology-based changes in fresh flowers, fruits, and vegetables will lessen the importance of careful and expedited handling, proper temperature and relative humidity maintenance, and effective sanitation procedures throughout the postharvest handling system.
C. M. Geraldson
The gradient concept, which has been used to provide nutritional stability in a field orientated full-bed mulch production system, is being evaluated as a component in a containerized concept. Conceptionally, the nutrient/water Input must be synchronized with removal. A built-in water table and a time-clock regulated microirrigation procedure were evaluated as water sources. A reservoir of soluble N-K banded at the media surface was used to maintain and evaluate the nutritional gradient. Container design, choice of media, plant populations and even dual containers are being evaluated and selected to enhance the functional efficiency of the concept. Yields of 6.8 to 13.6 kgs of marketable, above average quality tomatoes per plant have verified the feasibility of the concept. The containerized gradient concept using minimal water with minimal pollution and using the gradient approach to allow a maximum productivity with minimal management, has the potential to become a globally sustainable production system.
Eric A. Curry
Present dietary recommendations for fruits and vegetables should be based on the bioavailability of essential nutrients at the time of optimum harvest. Few people, however, are fortunate enough to have available freshly harvested produce all year. With the development of improved postharvest technology, shelf life has increased dramatically in many parts of the world. How does the nutritional quality of fruits and vegetables change with increasing storage time, changes in storage atmosphere, different postharvest processes? Do these changes have an impact on dietary recommendations? Apples are capable of being stored for up to 12 months with properly managed temperature and storage atmosphere. Because information regarding this subject is lacking for apple (and many other fruits and vegetables), perhaps a model can be developed based on work with other commodities to help us understand the nutritional changes associated with different postharvest treatments.
118 ORAL SESSION 23 (Abstr. 159–166) Nutrition–Vegetable Crops