Cloned Eucalyptus spp. plantations are based in greenhouse production of plants generated by vegetative propagation. Diverse studies have demonstrated that rhizospheric bacteria can stimulate plant growth, and more recently that they can increase rooting in vegetative material. Considering this potential, the objective of this study was to verify the effect of bacterial strains on rooting Eucalyptus globulus. A total of 132 bacterial strains isolated from the rhizosphere of E. globulus and Eucalyptus nitens were studied. The bacterial inoculums in a concentration of 4 9 10 8 cfu/ml were applied to the rooting substrate at the cutting installation and 45 days after by irrigation. Rooting was evaluated on days 60 and 75 after cutting installation, considering the number of roots as well as their fibrosity and roots biomass. Of the 132 strains evaluated, 26 significantly increased cutting rooting in a range of 191.4-69.4% with respect to the control. Additionally, some strains stimulated the development of fine roots and incremented the roots biomass. The strains identificated that produced a rooting effect were: Bacillus firmus, Bacillus mycoides, Bacillus stearothermophilus, Bacillus subtilis, B. subtilis/amyloliquefaciens, Bacillus circulans, Brevibacillus brevis, Paenibacillus lautus and Stenotrophomona maltophilia. These first trials suggest the potential of these bacteria to be used in clonal production programs for E. globulus.
The objective of this study was to determine the potential of antagonistic bacteria to control charcoal root rot of coniferous seedlings caused by Macrophomina phaseolina (Tassi) Goid. in forest nurseries. Bacterial isolates were collected from nurseries located between Region Metropolitana and the VIII Region of Chile. Antagonists were initially evaluated in in vitro assays based on the ability to inhibit mycelial growth of M. phaseolina, and subsequently in two trials in a Pinus radiata nursery with a natural infestation of the pathogen. For nursery trials, the isolates were selected according to in vitro and field trial pathogen controls. The bacteria were applied as seed treatments and via water irrigation. The trials were conduced in a completely randomized block design. Among 568 bacterial isolates tested in vitro, 19.8% displayed some capacity to inhibit the mycelial growth of M. phaseolina, with inhibition between 1.7% and 67.6%. In the first nursery trial, Bacillus amyloliquefaciens VII 015, Bacillus pumilus IX 030, Bacillus stearothermophilus TM 008 and other two Bacillus sp. (VI 009 and IX 049) strains, significantly reduced the total, pre-and post-emergency mortality of seedlings, but no isolate reduced the incidence of M. phaseolina in seedlings. In the second trial, Bacillus sp. IX 049, VI 099, B. subtilis (IX 007) and a non-identified isolate V 005, decreased the incidence of charcoal root rot. It is concluded that the best of these bacterial antagonists have the potential to control M. phaseolina in P. radiata nurseries.
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