The influence of Azospirillum baldaniorum Sp245 on cutting propagation and plant growth after transplantation in olive Leccino cultivar (Olea europaea L.)

The employment of plant growth promoting bacteria (PGPB) is a developing practice mainly involved under organic agricultural contexts. In particular, the use of alternative rooting agents may successfully contribute to the development of the olive sector propagation. This issue has let to assess the potential effect of the free-living soil bacteria Azospirillum baldaniorum Sp245 on olive cultivar ‘Leccino’ as i) root inductor for cuttings and ii) biostimulant on growth of nursery olive young plants. During the first nursery phase related to the rooting inductive process, comparative analyses were carried out between A. baldaniorum Sp245 and indole-3-butyric acid (IBA), a synthetic auxin usually used as root-promoting compound. Moreover, the bacterial suspension was periodically applied to the growing medium of hardened young plants, and compared with treatments by cell-free supernatant derived from the bacterial culture. Positive results were obtained on the assessment of the early histological changes related to the adventitious root formation. Interestingly, similar responses between cuttings treated with A. baldaniorum Sp245 and IBA were observed. Young plants provided with the bacterial suspension showed a general growing improvement of both hypogeal and epigeal apparatus. These features suggest that A. baldaniorum Sp245 could be usefully employed as rooting inducer, promoting a possible IBA replacing. Moreover, the improved quality of young olive plants determined by A. baldaniorum Sp245 supply, make it a profitable biostimulant in a context of organic nursery systems.