Extending the storage life of fresh cranberries (Vaccinium macrocarpon Ait.) requires an optimum storage environment to minimize decay and physiological breakdown (PB). To assess the effects of relative humidity (RH) and temperature on storage life, cranberry fruit from four bogs were stored over calcium nitrate, sodium chloride, or potassium nitrate salts, which maintained RH at 75%, 88%, and 98%, respectively. Containers at each RH were held at 0, 3, 5, 7, or 10 °C and fruit quality was evaluated monthly for 6 months. Both decay and PB increased with increasing RH in storage. After 6 months, 32%, 38%, and 54% of fruit were decayed and 28%, 31%, and 36% developed PB when stored in 75%, 88%, and 98% RH, respectively. The effects of RH continued to be apparent after fruit were removed from storage, graded, and held for 7 days at 20 °C. The decay of graded fruit after 4 months of storage in 75%, 88%, or 98% RH was 10%, 13%, and 31%, respectively, while PB was 12%, 12%, and 17%, respectively. Fresh weight loss decreased as RH increased averaging 1.9%, 1.4%, and 0.7% per month for storage in 75%, 88%, and 98% RH, respectively. Fruit firmness was not affected by RH. Storage temperature had little effect on decay. However, PB was greatest in fruit stored at 10 °C, encompassing 55% of fruit after 5 months of storage. When graded fruit were held an additional 7 days at 20 °C, decay and PB were greater in fruit previously stored at 0 or 3 °C than at 5, 7, or 10 °C. Fresh weight loss increased as storage temperature increased, averaging 0.8%, 1.0%, 1.3%, 1.7%, and 1.9% per month at 0, 3, 5, 7, and 10 °C, respectively. Fruit firmness decreased during storage, but was not affected by storage temperature. To maximize storage and shelf life, cranberry fruit should be stored in a RH of about 75% at 5 °C.
Charles F. Forney, Stephanie Bishop, Michele Elliot, and Vivian Agar
Stephen G. DeWald, Richard E. Litz, and Gloria A. Moore
Medium components and characteristics that affect the growth of embryogenic mango (Mangifera indica L.) nucellar cultures and production of somatic embryos in vitro were studied. These included the role of complex organic supplements, basal medium formulations, solidifying agents, and liquid vs. solid media. Growth of embryogenic cultures in suspension was more efficient than on solid medium; however, subculture onto solid medium was essential for high-frequency production of morphologically normal somatic embryos, and Gelrite was more effective in this respect than Difco Bacto-agar. Modified B-5 basal medium was better for maintenance of cultures and for production of morphologically normal somatic embryos than either Murashige and Skoog or Woody Plant Medium. Sucrose concentrations at 5% to 6% were optimal for somatic embryo production, and also increased the frequency of recovery of normally differentiated early heart-shaped somatic embryos. Coconut water (20%, v/v) enhanced somatic embryo production by 18%; other complex organic addenda alone or in combination with coconut water were either ineffective (casein hydrolysate) or highly inhibitory (yeast extract) in comparison with basal medium alone.
J. Frick and C.A. Mitchell
Due to its short time to flower (14-18 days) and rapid maturation cycle (50-55 days), dwarf rapid-cycling brassica (Brassica napus) is under consideration as a candidate oilseed crop for NASA's Controlled Ecological Life Support Systems program. Recent work has focused on defining a set of optimum environmental conditions which permit increased crop yield in terms of g·m-2d-1 of edible biomass. A wide range of environmental variables have been considered including lamp type, CO2 level, nutrient solution pH, and planting density. In addition, nitrogen nutrition regimes have been manipulated with respect to nitrogen concentration (2 to 30 mM), source (NH4 + and/or NO3 -), and time of stepwise changes in nitrogen level (day 14 to 28). The highest seed oil content (42% DW basis) has been found under limiting nitrogen levels (2 mM). However, the low nitrogen inhibits overall seed production potential. Different cultural techniques also have been compared, including solid-substrate, passive wicking hydroponics versus liquid culture systems. Trials are underway to assess crop growth and development under the “best set” scenario of environmental conditions. At present, the highest seed yield (10.6 g·m-2d-1) has been obtained using solid-substrate hydroponic systems under a combination of metal halide and high-pressure sodium lamps. Constant CO2 enrichment to 1000 μmol·mol-1 did not increase crop yield rate.
Research supported in part by NASA grant NAGW - 2329.
Maynard E. Bates
Increased production and reduced costs are goals of all plant growers. As a rule, introduction of computer-based control of the plant environment in a well-designed greenhouse will result in yield increases of thirty percent (30%) over other control techniques. A simple model will show how these changes impact profitability.
New technologies in sensors, interfaces, computers, software, and plant growth knowledge are being applied to management of the crop environment. Examples of direct canopy temperature measurement, online plant weight measurement, integration and control of photosynthetic photon flux, and nutrition control will be presented. Integrated process control is replacing setpoint maintenance. Models are being developed for incorporation into environmental control systems. Examples for solar irradiance and crop growth will be demonstrated.
Ultimately expert systems based on artificial intelligence technology will manage crop production in controlled environments. These systems will incorporate information on crop genome, local climate, cultural practices, pests and diseases, economics, and markets, in addition to environmental control. A possible configuration of the hardware and software for such a system will be discussed.
M. K. Schon and M. P. Compton
Experiments were conducted to determine the optimum levels of N and P for use in greenhouse cucumber (Cucumis sativus L. `Vetomil') production. Plants were grown in rockwool slabs using a double-stem pruning method. Treatment 1 plants were fed 90 ppm N until N in the growing slabs was depleted (averaged <10 ppm); N was then increased to 175 ppm. Treatment 2 and 3 plants were given a constant 175 or 225 ppm N, respectively. Plants in all treatments depleted N in the slabs by three to four weeks after transplant (WAT); N remained low in Treatment 1, but recovered to adequate levels in Treatments 2 and 3. Phosphorus was provided at a constant 50 ppm and was depleted to <10 ppm in the slabs of all three treatments by four WAT. Fruit yield increased significantly with each increase in solution N. Similar results in a second trial indicated that N and/or P may have been limiting factors even at the highest levels tested. Research will continue to determine optimum levels of N and P for maximizing yield.
Otho S. Wells
Tomato production in high tunnels is very intensive, although relatively low-input. However, optimal use of every square foot of growing space is critical to maximizing returns. Utilizing the basket-weave trellis system, `Ultrasweet' tomatoes were grown in 4 (replicated), 14-foot-wide high tunnels in 4 rows per tunnel at 3.5 ft between rows. In-row spacing of 12, 18, and 24 inches was combined with removal of sideshoots below the first flower cluster: one or three shoots at 18 and 24-inch spacing and none or one at 12-inch spacing. The highest marketable yield per plant was 22 lbs at 24 inches and three sideshoots, while the lowest yield per plant was 13.9 lbs at 12 inches and no sideshoots. The highest yield per sq ft was 4.2 lbs at 12 inches and no sideshoots, while the lowest yield per sq ft was 2.5 lbs at 24 inches and one sideshoot. The yield response to spacing and side-shoot removal was inverse for lbs per plant and lbs per sq ft. There was no difference in fruit size among any of the treatments. In a comparable experiment under field conditions, the highest yield per plant was 12.6 lbs at 24 inches and one sideshoot; and the highest yield per sq ft was 2 lbs at 12 inches and one sideshoot. The percentage of marketable fruit in the tunnels and in the field was 93.0 and 85.1, respectively.
Theresa Bosma, John Dole, and Niels Maness
Marigold flower pigments can be extracted and used as a natural source of food colorants in the poultry and dairy industry. These pigments impart an orange color to egg yolks and a yellowish color to dairy products. We examined four African marigold cultivars for their ability to be commercially grown and harvested mechanically. `E-1236' yielded the highest quantity of lutein (22 kg/ha), a carotenoid pigment, using a spectrophotometer for quantification. `E-1236' and `A-975' were the earliest flowering cultivars, 11 June 1998 for transplants and 9 July 1998 for direct-seeded, at 8 weeks after sowing regardless of field establishment method. `E-1236' produced the greatest number of flowers in a production season, both as transplants (68 flowers/plant) and direct-seeded (57 flowers/plant) at 363,290 plants/ha. Transplants resulted in two more harvests in a single season than direct-seeded plants. Subsequently, more flowers and petal material were produced for pigment extraction than with direct-seeded plants. A one-time application of ammonium nitrate (28.02 kg/ha) at mid-season did not significantly effect flower number, flower weight, or pigment yield. Experiment was repeated in 1999 with four cultivars, two field establishment methods, seven harvest dates, and five nitrogen applications.
C.L. Boehm, I.K. Lee, G. Jung, H.C. Harrison, J. Nienhuis, M. Sass, and Moore Hall
Random amplified polymorphic DNA (RAPD) may have utility as genetic markers facilitating selection in ginseng crop improvement. This experiment determined chemical buffer and root tissue-type combinations that yield repeatable bands. The results allow further experiments using RAPD markers for estimating the genetic distance between ginseng landraces, selection for crop improvement, and extensive fingerprinting for use in determining the origin of tissue samples. This experiment determined mean band yields for all combinations of dry, fresh, and powdered root with cetyltrimethylammonium bromide, potassium/sodium ethyl xanthogenate, and urea buffers. The buffers were applied in replication to the tissue-types with other extraction protocol factors constant. Replications were amplified four times with four different primers using constant PCR and agarose gel electrophoretic protocols. Distinct bands were counted in each replication, and the summation of the replication repeats considered an observation. Least squares means for several response variables were analyzed. The most significant difference found was between buffers. The buffers ctab and urea were productive, and the pex was not. Significant difference was found when buffers were crossed with tissue. The applications of urea to fresh root, ctab to dry root, urea to dry root, and ctab to powdered root were productive. Based on these results we conclude 1) urea and ctab are productive when applied to all tissue-types, 2) dry root, which is easily collected and stored, yields sufficient DNA for analysis, and 3) powdered root, often the form of commercial products that might be tested for genetic origin, will yield sufficient DNA for analysis.
Ruwanthi C. Wettasinghe and Ellen B. Peffley
Random amplified polymorphic DNA (RAPD) have potential as genetic markers that may facilitate selection in plant improvement. To obtain clear, reproducible, and repeatable RAPD bands, four DNA extraction protocols and two Taq polymerases were compared. DNA extraction followed modified Tai and Tanksley (PMBR), Dellaporta et al. (PMBR), and Guilllemant et al. (PMBR) protocols, and a plant tissue DNA isolation kit from Gentra Systems was used. The modified Guillemant protocol was selected because of ease of extraction and cost effectiveness. Genotypes studied were TG1015Y (Allium cepa). Polymerases compared were Taq and Taq Stoffel fragment. Results are based on separate amplifications and electrophoretic assays. PCR amplifications of Stoffel fragment produced more scorable and reproducible RAPD bands compared to bands produced using Taq polymerase.
J. Michele Myers and Philipp W. Simon
We evaluated the efficiency of transformation in garlic for promoter activity, osmoticum effect and shaker speed using particle bombardment as the method of gene delivery. Callus was produced from root segments on a modified B-5 medium for four garlic clones. Suspension cultures were then established on a modified B-5 medium + 2,4-D using 6-month-old callus. Cells were collected by vacuum filtration and the Bio-Rad PDS-1000/He system was used to deliver genes. The activities of CaMV 35S, maize Adh1, and rice Act promoters were evaluated for transient expression using the β-glucuronidase (GUS) reporter gene. Osmotic conditioning of cells was performed by adding both mannitol and sorbitol to the medium. Osmoticum effect was evaluated for enhancement of transformation efficiency using GUS. The effect of shaker speed (120, 180 and 240 rpm) on cell type was evaluated for transformation efficiency using GUS. CaMV 35S promoter activity was much higher for garlic than either the maize Adh1 or rice Act promoters. Osmoticum did not enhance promoter activity, but differences in response to osmoticum among garlic clones were observed. Shaker speed did affect cell type, and transformation efficiency was greatly increased at higher shaker speeds. Confirmation of stable transformation and regeneration are in progress.