title: Biofertilization with Azospirillum brasilense improves in vitro culture of Handroanthus ochraceus, a forestry, ornamental and medicinal plant.
abstract: Biofertilization with plant growth-promoting rhizobacteria is a potential alternative to plant productivity. Here, in vitro propagation of Handroanthus ochraceus (yellow lapacho), a forest crop with high economic and environmental value, was developed using the Azospirillum brasilense strains Cd and Az39 during rhizogenesis. Epicotiles of in vitro plantlets were multiplied in Woody Plant Medium (WPM). For rooting, elongated shoots were transferred to auxin-free Murashige-Skoog medium with Gamborg's vitamins and WPM, both at half salt concentration (½MSG and ½WPM), and inoculated with Cd or Az39 at the base of each shoot. Anatomical studies were performed using leaves cleared and stained with safranin for optical microscopy and leaves and roots metalized with gold-palladium for scanning electron microscopy (SEM). In ½WPM auxin-free medium, A. brasilense Cd inoculation produced 55% of rooting, increased root fresh and dry weight (45% and 77%, respectively), and led to lower stomata size and density with similar proportion of open and closed stomata. Both strains selectively increased the size or density of glandular trichomes in ½MSG. Moreover, bacteria were detected on the root surface by SEM. In conclusion, the difference in H. ochraceus response to A. brasilense inoculation depends on the strain and the plant culture media. Cd strain enhanced rooting in auxin-free ½WPM and produced plantlets with features similar to those expected in ex vitro plants. This work presents an innovative in vitro approach using beneficial plant-microorganism interaction as an ecologically compatible strategy in plant biotechnology.
authors.affiliation: Plant Tissue Culture Laboratory (CULTEV), Department of Basic Sciences, National University of Luján, CC221 Luján (B), Argentina. Electronic address: bllorente@gmail.com.
authors.forename: Berta E
authors.initials: BE
authors.lastname: Llorente
authors.affiliation: Plant Tissue Culture Laboratory (CULTEV), Department of Basic Sciences, National University of Luján, CC221 Luján (B), Argentina.
authors.forename: María A
authors.initials: MA
authors.lastname: Alasia
authors.affiliation: Plant Tissue Culture Laboratory (CULTEV), Department of Basic Sciences, National University of Luján, CC221 Luján (B), Argentina.
authors.forename: Ezequiel E
authors.initials: EE
authors.lastname: Larraburu
mesh_terms: D000704:Analysis of Variance; D015806:Azospirillum brasilense / Q000502:physiology*; D005163:Factor Analysis, Statistical; D005308:Fertilizers; D016468:Forestry; D019686:Lamiaceae / Q000166:cytology / Q000254:growth & development* / Q000648:ultrastructure; D018517:Plant Roots / Q000502:physiology / Q000648:ultrastructure; D010946:Plants, Medicinal / Q000166:cytology / Q000254:growth & development* / Q000648:ultrastructure; D046509:Tissue Culture Techniques / Q000379:methods*
chemical_list: D005308:Fertilizers