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  • Author or Editor: Ellen Peffley x
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(Allium cepa × A. fistulosum) × A. cepa breeding lines have been established to the fourth generation. The aim is to develop an A. cepa-like bulbing onion carrying A. fistulosum genes. Seven populations were characterized for morphological traits and three isozyme markers. Each bulb from the populations was characterized for maturity, soluble solids content, bulb shape, and bulb color. All the populations produced A. cepa-like bulbs. Significant variation was observed within each population for each morphological trait. All the bulbs were screened for the presence of A. cepa and A. fistulosum alleles of alcohol dehydrogenase (Adh-1), esterase (Est), and phosphoglucoisomerase (Pgi-1). Allium cepa Adh-1, Est, and Pgi-1 alleles were observed in all the populations. One population, 951026-8, contained plants heterozygous for A. cepa and A. fistulosum Pgi-1 alleles. Recovery of these fourth generation Allium backcross plants demonstrates introgression of the A. fistulosum genome into an A. cepa-like bulbing onion.

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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.

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Introgression of genes in species crosses can be observed morphologically in backcrossed or selfed progenies, but the phenotype does not give information about the movement of DNAs. Cytogenetic markers allow for visualization of specific DNAs in a genome. Few cytogenetic markers are available in onion to monitor the introgression of DNA in species crosses. Genomic in situ hybridization (GISH) provides a way to locate unique DNA sequences contributed by parents. We are using GISH to monitor the movement of DNAs from A. fistulosum into A. cepa. Results of experiments using A. fistulosum as probe DNA, and A. cepa as blocking DNA will be reported. Also presented are hybridization sites observed in F1BC3 progeny of the GISH.

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The concept that plants and humans in a living system are mutually beneficial was communicated to 2nd to 12th grade students in science educational and outreach programs at Texas Tech University's Center for Space Science. Students traveled to the TTU horticulture greenhouse for a live program, which focused on research in the Engineering Development Unit. The research is funded by NASA's Advanced Life Support. During the program students were presented with the science of growing plants, how plants benefit humans in space, and baseline science vocabulary. A survey instrument was developed to assess student level of understanding of sciences, and their comprehension of living cycles, which work together to support manned space missions. The survey consisted of multiple-choice questions covering topics presented during the program. Likert questions were used to assess student's desire to travel in space, be an astronaut or a scientist, and their enjoyment of science and growing plants. The survey was administered before the program; immediately after the program; and a delayed test was administered in their classroom several weeks after the program. Student performance was scored according to correct responses in the survey. Responses were analyzed for changes over time using an analysis of variance with repeated measures. The results showed there was an overall improvement in knowledge from preprogram survey to postprogram survey and that students recognize science is the main topic to be studied to expand for better space programs. Some elementary education students scored equal to or higher than secondary education students. Enthusiastic science teachers may drive student interest exhibited in the early grades. There is evidence that a teacher's attitude towards science and one's basic science knowledge is important to molding student's attitudes and interests in science.

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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.

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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.

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Random amplified polymorphic DNA (RAPD) are genetic markers that facilitate selection in plant breeding. To obtain clear reproducible, and repeatable RAPD bands, four DNA extraction protocols and two Taq polymerases were compared using thirteen TG1015Y (Allium cepa) genotypes. Protocols for DNA extraction followed those of a modified Tai and Tanksley, 1989 (PMBR); a modified Dellaporta et al., 1983 (PMBR); a modified Guillemunt et al., 1992 (PMBR); and extracted with a plant tissue DNA isolation kit from Gentra System (Minneapolis). The modified Guillemunt protocol was selected due to ease of extraction and cost effectiveness. Polymerases compared were Taq and Taq Stoffel fragment. Results are based on three separate amplifications and electrophoretic assays. PCR amplifications of Stoffel fragment produced more scorable and reproducible RAPD bands compared to bands produced using Taq polymerase.

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Particle bombardment was investigated as a potential transformation method for onion. Seeds of Allium cepa `TG 1015' were planted onto BDS medium and placed in a dark incubator at 25C for germination. Two to 3 weeks after the seeds were germinated, meristems (1 to 2 mm) were excised and placed onto BDS medium containing 2 mg 2,4-D/liter for callus initiation. Callus was transferred monthly onto fresh BDS medium containing 2,4-D until bombardment. The reporter gene for B-glucuronidase (GUS) expression was used to assess efficiency of gene delivery in all particle bombardments. Characteristics examined were target distance and helium pressure (particle velocity). Tissues were subjected to the 5-bromo-4-chloro-3-indoyl-B-D-glucuronide (xgluc) test for detection of GUS activity. Measurements were taken on particle dispersion as affected by target distance and helium pressure. GUS expression was detected in putatively transformed tissues.

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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.

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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.

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