Proponents of distance education encourage the migration of courses and entire degree programs onto the web. To this end, vast amounts of time, energy, and funds are directed to the development of new courses as well as the enhancement of traditionally taught courses. The question now begs to be asked, “Are we getting what we truly want from distance education?” Using a web platform provides a framework with excellent options to develop audio and visually rich courses. Distance programs also provide access to students not able to participate in traditional on-campus degree plans, providing the potential for a boost in enrollment. However, there are serious considerations that need to be balanced, including student satisfaction/dissatisfaction, enrollment management, faculty time commitment, and technical support. In this presentation, some of the benefits and liabilities of web courses will be discussed and program management suggestions will be explored.
Teaching at a distance has many rewards and challenges inherent in its delivery. Interactive video conferencing has the advantages of having audio and visual contact with students during a set class period while having the disadvantages of scheduling multiple locations and keeping the equipment functioning at peak performance. Likewise, using a web platform such as WebCT provides a framework with excellent options to develop a course that is both audio and visually rich. This solution also presents its own difficulties as required textbooks change and the platform version may be upgraded. In this presentation, the advantages and disadvantages of both formats will be reviewed. In addition, helpful hints for blending these two teaching methods together to create a custom course will be discussed.
Horizontal starch gel electrophoresis was used to study the inheritance of isozyme phenotypes of four enzyme systems [alcohol dehydrogenase (ADH), 6-phosphogluconate dehydrogenase (6-PGDH), phosphoglucomutase (PGM), and shikimate dehydrogenase (SKDH)] in Allium fistulosum L. by monitoring segregations in backcross and F2 progeny. Segregation for most of the polymorphisms fit the expected Mendelian ratios as tested by the chi-square statistic. Three new isozyme loci were defined for onion. Two loci were found for 6-PGDH. Locus one was dimeric with two alleles, and locus two was monomorphic. SKDH was monomeric with two alleles.
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.
Over the past several growing seasons researchers at Texas Tech University have observed that certain onions appeal to rabbits more than other onions, meaning that rabbits tend to nibble on certain lines or varieties and leave other lines undisturbed. We were interested in determining the cahracteristics of the onions that rabbits seemed to like. Onions were planted at random in the TTU breeding nursery. During the growing season all onions were rated for rabbit appeal - those with chewed leaves and or bulbs were recorded as liked by the rabbits. All onions in each plot, whether disturbed or undisturbed by the rabbits, were tested for pyruvate concentration and soluble solids content after harvest. Pyruvates were measured by mmol/gram pyruvic acid and soluble solids content by °Brix refractometer reading. The most damage occurred in onion lines that had the lowest pyruvate levels. Soluble solids did not appear to affect the rabbits' nibbling.
Horizontal starch gel electrophoresis was used to study the mode of inheritance of isozyme phenotypes of four enzyme systems (ADH, 6-PGDH, PGM, and SKDH) in Allium cepa L. and A. fistulosum L. by monitoring segregations in backcross and F2 progeny. Segregation for most of the polymorphisms fit the expected Mendelian ratios as tested by the chi-square statistic. Three new isozyme loci were defined for onion. 6-phosphogluconate dehydrogenase was dimeric in structure, with two alleles present at the first locus, while a second locus was monomorphic. Shikimate dehydrogenase was monomeric with two alleles.
The inheritance and linkage relationships among PGM-1, ADH-1, and 6-PGDH-1 were determined for Allium fistulosum (Japanese bunching onion) individuals. Individuals expressing Pgm-11/Pgm-12, Adh-13/Adh-14, Adh-13/Adh-15, or 6-Pgdh-11/6-Pgdh-12 were selfed seperately. These backcrosses and their reciprocals were made: Pgm-11/Pgm-12 to Pgm-11/Pgm-11 or Pgm-12/Pgm-12; Adh-13/Adh-14 to Adh-13/Adh-13 or Adh-14/Adh-14, 6-Pgdh-11/6-Pgdh-12 to 6-Pgdh-11/6-Pgdh-11 or 6-Pgdh-12/6-Pgdh-12. Progeny segregations were tested for Mendelian inheritance using a chi-square goodness of fit test. Expression of 6-Pgdh has not been previously reported in onion. Two zones of activity were detected and were designated as 6-PGDH-1 and 6-PGDH-2. 6-PGDH-2 was monomorphic for all individuals tested. Progeny segregation of 6-PGDH-1 fit a model for a dimeric enzyme encoded by one disomic locus with two alleles, expressed as fast (1) and slow (2), in a dimeric enzyme pattern in heterozygous individuals.
Nineteen random primers yielded 36 PCR-amplified products of Allium cepa profiles of each of 15 short-day grano-type onionsgrown commercially in Texas and Southern United States were compared. Several PCR productswere unique among the cultivars and can be used to differentiate among the onion cultivars investigated. A phenogram of the cultivars based on the co-occurrences of the PCR products was derived.
Callus of five onion genotypes representing two species. Allium cepa and A. fistulosum, and their interspecific hybrid were used for establishing suspension cultures. Cultures were derived from callus that had been maintained on solid media and routinely subcultured for four years and from callus induced within six months of this experiment. Long-term callus from which plants were routinely regenerated and newly-induced callus were composed of cells which were, for the most-part, meristem-like with higher mitotic indices than cells from long-term callus which had been maintained as callus but had lost us capability to regenerate plants, these cells were large with small nuclei. Callus from newly-induced and long-term regenerable cultures were selected for further studies. Eight liquid media with factorial combinations of plant growth regulators were tested. Cells cultured in BDS liquid medium supplemented with 0.5 mg/l ABA and 1.0 or 2.0 mg/l 2,4-D without e-BA had higher mitotic indices and plant regeneration percentages than did cells cultured in the same media without ABA and with 6-BA. Suspension cultures from A. fistulosum and interspecific hybrids with A. fistulosum produced the highest numbers of plants regenerated.
This research evaluated for the NASA ALS program the effect of plant spacing on edible biomass of green salad onions. The ontogeny of Japanese bunching onion, A. fistulosum; bulbing onion, A. cepa; and chives, A. schoenoprasum grown at 10, 15, and 20-mm spacings harvested weekly were compared. Onions were grown hydroponically in Environmental Growth Chambers 16 hours light/8 hours dark, 24/20 °C, 75/99%, ≈650 μmol·m–2.
Experimental design was a completely randomized block with repeated measures. Subsamples of plants completely surrounded by neighboring plants were chosen at random from experimental units. Weekly removal of shoots began 28 days after planting (dap); destructive harvest was 70 dap. Length and diameter of longest leaf, weight (g), number of leaves/tillers were recorded weekly. Bulb caliper and weight was taken 70 dap. Bunching and bulbing onion leaves were longest at 28 dap; leaf lengths steadily decreased over time. Chives were slower to germinate and establish but at 70 dap had longest leaves of all species. Leaf diameter of all species increased as spacing increased. At 56 and through 70 dap chives at all three spacings produced more leaves. Mean weight of shoots differed significantly at the 20-mm spacing: chives weighed the least and bulbing onion the most. Bulb weight for bulbing onion and chives increased with increased spacing; bulbing onion weighed significantly more at 15 and 20-mm compared to the other species and spacings. Chives grown at 20-mm had tillering clumps of rhizomes. Total edible biomass weight (bulb, pseudostem, shoots) of bulbing onion grown at 10-mm exhibited similar ontogeny to chives grown at 10 and 15-mm spacings; bulbing onion grown at 20-mm had the most edible biomass.