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.
Anfu Hou and Ellen B. Peffley
Charles Macharia and Ellen B. Peffley
The genus Amaranthus contains many species which are common weeds found on the Texas high plains. In a field experiment plant height and numbers of plants of Amaranthus varied when grown with different Allium genotypes: Allium fistulosum var. `Heshiko' and an interspecific F1 hybrid 81215 (Heshiko × A. cepa cv. `New Mexico Yellow Grano'). The genotypes that showed no allelopathic effect were A. cepa cv `New Mexico Yellow Grano', A. fistulosum var. `Ishikura', and their F1 hybrid 8273. On the basis of these observations experiments have been done to quantify the degree of suppression. A randomized complete block design was used under greenhouse conditions in order to measure growth characters of Amaranthus.
Song Ping and Ellen B. Peffley
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.
Amanda Broome and Ellen B. Peffley
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.
Melissa Neal and Ellen B. Peffley
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.
Cynthia B. McKenney and Ellen B. Peffley
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.
Cynthia B. McKenney and Ellen B. Peffley
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.
Paul D. Mangum and Ellen B. Peffley
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.
Ping Song, Wanhee Kang, and Ellen B. Peffley
Regenerating calli of Allium fistulosum × A. cepa interspecific F1 hybrids were treated in vitro with colchicine. A factorial experiment (colchicine concentration × time) was used to recover tetraploids from calli treated with colchicine in vitro. Shoot production of regenerating calli following in vitro colchicine treatment decreased with increasing colchicine concentration and treatment time. Cytological analyses of root tip cells from regenerated plantlets showed that chromosomes of control plantlets (not treated with colchicine) were not doubled. Chromosomes of some plantlets regenerated from in vitro colchicine treated calli were doubled, resulting in tetraploids. Calli treated with 0.1 or 0.2% colchicine in BDS (Dunstan & Short, 1977) liquid medium for 48 or 72 hours yielded the highest number of tetraploid plantlets. These results demonstrate that in vitro colchicine treatment of regenerating calli of interspecific F1 hybrids is effective in recovering tetraploids.
Ellen B. Peffley and Melanie A. Hart
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.