Assessing the effect of Azospirillum baldaniorum Sp245 on rooting ability of olive cuttings (Olea europaea L., cultivar Santa Caterina)

To promote adventitious root initiation and formation in olive cuttings, auxins are the most widely used hormonal agent, indole-3-butyric acid (IBA) resulting particularly effective. However, IBA has been found ineffective in low rooting ability cultivars and there are evidences about phytotoxic effects. Therefore, the employment of biological agents such as rhizobacteria, and the implement of biological treatments instead of conventional chemical products are strongly encouraged. Thus, a study was conducted on the table olive cultivar Santa Caterina which is characterized by a very low rhizogenic capacity. Semi-hard wood cuttings were inoculated with Azospirillum baldaniorum Sp245, recognized as a plant-growth-promoting rhizobacterium, in comparison with exogenous applications of IBA. Parameters such as presence of callus, number of rooted cuttings, number and length of roots were evaluated. The experiment was conducted in sub-optimal growing conditions using a simple, inexpensive and not specialized propagator system. The overall results showed a noticeable improving of the rooting performances when cuttings were treated with the bacterial suspension. In comparison with IBA, an increase in rooting ability, number of adventitious roots and mean root length was obtained. These encouraging findings might lead to develop innovative organic protocols to perform a straightforward, environmentally sustainable olive propagation.