No abstract

In vitro grown shoot tissue of facultative apomictic lines of guayule (Parthenium argentatum Gray), a rubber producing desert shrub, were transformed by Agrobacterium-mediated DNA transfer and regenerated into complete plants. Guayule shoots of lines 11591, UC101 and UC104 were inoculated with A. tumefaciens strains LBA4404 or PC2760 harboring the binary vector pCGN1557. Axillary shoots were regenerated from transformed cells and rooted in vitro in the presence of kanamycin. Genetic transformation in all cases was verified by Southern blot analysis. Transgenic plants were grown to maturity in the greenhouse and, as predicted for apomictic species, all seed produced possessed kanamycin resistance. Because apomicts have limitations for gene transfer by normal sexual crosses, this method offers a new means of transferring genes into this species.Abbreviations: BA -benzyladenine; EDTA -ethylene diamine tetraacetate; kanR -kanamycin resistance; MS salts -salts of Murashige and Skoog medium (1962); NAA -naphthalene acetic acid; NPT-II -neomycin phosphotransferase; SDS -sodium dodecyl sulfate

Tissue culture methods have been developed for a number of desert-adapted species which have potential economic value. These species include gum tragacanth (Astragalus gossypinus), candelilla (Euphorbia antisyphilitica), guayule (Parthenium argentatum), cliff rose (Cowania stansburiana and C. subintegra), bottle tree (Brachychiton populneum), red squill (Urginea maritima), Arizona agave (Agave arizonica), and spider lily (Pancratium littorale). Axillary shoot proliferation for the dicotyledenous species of this group is induced using concentrations of 2 mg/L BAP, whereas the rooting requirements vary considerably. Micropropagation of the bulb-producing species, is accomplished by aseptic culture of bulb scales in darkness, followed by shoot proliferation of the bulblets and rooting. Micropropagation of Agave requires adventitious shoot formation from a callus intermediate followed by direct caulogenesis from subculture shoots and subsequent rooting.The potential benefit of these desert-adapted species and the usefulness of the micropropagation procedures will be discussed.