ABSTRACT
The aim of this work was to explore the possibility of obtaining transgenic plants of onion varieties cultivated in Argentina, starting from calli induced from mature zygotic embryos, using two strains of Agrobacterium tumefaciens as transfection vectors. Mature embryos from three varieties of 'Valenciana' onion, Torrentina, Cobriza INTA and Grano de oro were in vitro cultivated for callus induction. After three to four months an average of 57.4 percent success for the three varieties was reached. Transformation was carried out with Agl1 or LBA 4404 A. tumefaciens strains, both carrying a binary vector containing the marker gene gus a and the selection gene nptII. Selection was done in callus induction medium containing 10 mgL-1 geneticin during three subcultures. At the end of the selection period, 342 portions of calli were recovered and transferred to regeneration medium. Of the selected calli evaluated by the expresion of the beta-glucuronidase enzyme, 42 percent presented extensive blue areas or were completely blue. At the end of the first subculture in the regeneration medium, 54 calli were considered potentially organogenic because of the green areas observed. At the end of the wole regeneration period, just one normal plant was obtained, that was negative to PCR analysis using specific primers for gus a and nptII. All selected calli came from the Torrentina variety and the highest quantity of them were transformed with the strain LBA 4404.
ABSTRACT
Several mineral compounds influence adventitious rooting, and those containing boron and calcium, play an important role. They are associated to the enzyme regulation, cell division, cellular metabolism (induction stage) and roots enlargement (expression stage). The aims of this work were to study the variation of the endogenous calcium and boron concentrations along the rooting, and determine their optimal concentrations in the rooting basal medium of Nothofagus nervosa. Significant variation in endogenous calcium concentrations was detected along the rooting phase, strongly correlated with rhizogenesis phenomenons and linked to total peroxidase variation as cited elsewhere. Calcium and boron concentrations in the basal medium significantly affected the rooting. Treatment containing 60 mg.L-1 Ca and 1 mg.L-1 B produced root formation in fewer days than other combinations. The variation of these nutrient concentrations in the medium is a useful tool to improve microcutting rooting. Roots are obtained earlier and in a shorter period of time, finally resulting in more homogeneous microplants with a better developed rooting system.