Effect of Root-promoting Products in the Propagation of Organic Olive (Olea europaea L. cv. Cornicabra) Nursery Plants

Olive cuttings root well using synthetic auxin indole-3-butyric acid (IBA). However, European and North American regulations do not allow the use of synthetic products to obtain organic vegetative propagation materials. In this work, we evaluated different products that could replace IBA in the propagation of olive cv. Cornicabra leafy-stem cuttings. In 2003, six products with a known auxin effect were assessed: IBA, algae extract, brewer's yeast, a bed of sunflower seed, seaweed dry extract (Sm-6 Organico (TM)), and an extract of macerated seeds (Terrabal Organico (TM)). The basal end of cuttings was treated with one of these products and placed on a mist bed with basal temperature control. After 2 months, rooting percentage, number of roots per cutting, number of cuttings with callus formation, and number of cuttings with basal thickening were determined. No significant differences were found in rooting percentage or number of roots per cutting between IBA and Terrabal Organico (TM) and Sm-6 Organico (TM). These last products had significantly higher percentage of rooted cuttings without callus formation than IBA. In 2004, a new trial was conducted in which seven treatments were evaluated: IBA applied for 7 s; Terrabal Organico (TM) applied for 1, 4, and 8 h; and Sm-6 Organico (TM) applied for 1, 4, and 8 h. No significant differences in rooting percentage or number of roots per cutting were observed between IBA and Terrabal Organico (TM) applied for 1 h, whereas all the Sm-6 Organico (TM) treatments had significantly lower rooting percentages than IBA. Both rooting percentage and the percentage of rooted cuttings without callus development decreased significantly as treatment duration with Terrabal Organico (TM) increased. Therefore, Terrabal Organico (TM) could produce a toxic effect on cuttings when treatment duration is increased. Thus, Terrabal Organico (TM) could be a valid alternative to IBA in the propagation of organic olive plants of cv. Cornicabra when applied to the basal end of cuttings for 1 h.