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- Author or Editor: E. B. Peffley x
Interspecific F1 hybrid plants between Allium fistulosum L. and A. cepa L. exhibit bivalent pairing suggesting genomic homology; however, chromosomal variants exist rendering meiotic abnormalities. The occurrence of multivalent associations suggest at least 1 translocation differentiates the 2 species. The chromosome bearing the nucleolus organizer is apparently involved in the translocation. The presence of bridges and fragments in anaphase and telophase I also indicates the occurrence of at least 1 inversion. A minimum of 2 heteromorphic bivalents were observed which probably reflects the translocation and/or inversion(s).
The Department of Plant and Soil Science at Texas Tech University has developed on-line master's of science nonthesis and master's of agriculture nonthesis degree programs in response to the perceived needs of mature place bound students. Initial enrollments have been successful. The development of these types of programs requires time, funding and technically capable personnel. In addition, there are administrative, curricular and personnel issues involved with the implementation of such a project. These issues and the solutions we have employed will be discussed.
Total genomic DNA was isolated from study plants and was hybridized with 32P-labeled Allium fistulosum `Ishikura' genomic DNA; Southern blots were performed. Plant materials were Allium cepa `New Mexico Yellow Grano', the Allium fistulosum `Heshiko' and `Ishikura', and their F1 interspecific (Allium fistulosum × Allium cepa) hybrids. Sequences with high identity to the labeled DNA hybridized strongly (i.e., A. fistulosum `Ishikura' hybridized most strongly to itself, next with A. fistulosum `Heshiko'). The least hybridization was observed when A. fistulosum `Ishikura' was hybridized with A. cepa `New Mexico Yellow Grano'. Intensity of the signals observed when DNA of the F1 interspecific hybrids was probed with the `Ishikura' DNA was as expected, with the signals intermediate between those of A. fistulosum to A. fistulosum and A. fistulosum to A. cepa. A second study was performed to identify additional cytological markers in Allium. The 5srDNA and NOR genes from Triticum aestivum onto onion chromosomes using in situ hybridization. Evidence of hybridizations are the presence of fluorescing areas on the chromosomes.
Breeding programs depend upon genetic variation. Visual plant markers traditionally have been used in crop improvement. However, molecular markers provide additional selection criteria. Of the molecular markers available, isozymes are preferred by many researchers because they are expressed in young tissue as codominants and are easily extracted and detected. Mature plants may bias estimation of hybrid purity, whereas estimations of hybrid purity can be obtained at an early stage by enzyme analysis (1, 2, 4).
The horticulture faculty at Texas Tech Univ. has developed an introductory horticulture laboratory course offered asynchronously through several media. A print version has been developed as a traditional correspondence course. Students can also choose to access the course over the World Wide Web with laboratory instruction provided from an accompanying CD-ROM. The course is based on an introductory horticulture textbook and is supplemented by additional information. Students conduct the laboratory exercises at a location of their choice and return photographs or video tapes of their results along with a formal lab report. Self-help exercises, worksheets, and proctored exams are submitted by correspondence or electronically via the World Wide Web. The most challenging aspect of this project was the development of laboratory exercises that ensured adequate experiential learning. This was accomplished by using easily accessible materials for laboratories that would allow students to apply the scientific method. A CD-ROM version of the lab includes compressed video segments used to demonstrate laboratory techniques. Details of these laboratory components and samples of student work will be presented.
Field grown onion plants (Allium cepa L. cvs. New Mexico Yellow Grano and Yellow Granex) harvested in December were frozen in a laboratory freezer were removed from the freezer at about 1°C intervals and replanted in sand in a warm greenhouse. Criterion for survival was root regeneration within 3 weeks. The LT50 value as determined by probit analysis for 58-day-old plants (−8.8°C) was significantly higher (0.5% level) than for the 74- or 90-day-old plants (−10.5 or−10.8°C) indicating less cold hardiness for the youngest plants.
Particle bombardment using the Bio-Rad PDS-1000/HE system is being investigated as a means to develop a stable transformation system for the bulb onion. Donor materials for bombardments included sterile meristems and radicals from newly germinated seeds, callus of Allium cepa `TG1015', `Sunlite', and `Buffalo', A. fistulosum `Heshiko', and suspension-cultured cell lines with confirmed regeneration capability, as well as regenerated plants of an F1 interspecific hybrid. Transient expression assays using the B-glucuronidase (GUS) reporter gene system were used to optimize the conditions for transformation. Various promoters combined with the GUS coding sequence were tested. Results indicate genotype specificity for promoter expression. Some tissue continued to exhibit GUS activity after several months in culture, indicating potential for achieving stable transformation of onion.