Influence of (22S, 23S)-homobrassinolide on olive rooting

Brassinosteroids (BRs) have been used in woody plants to increase the rooting response. In this research, (22S,23S)-homobrassinolide (SSHB) was tested, alone and in combination with indole-3-butyric acid potassium salt (K-IBA), to promote olive clonal propagation. In November 2014, cuttings of two Italian cultivars, 'Leccino' (easy to root) and 'Leccio del Corno' (difficult to root), were collected and forced to root. Two studies were carried out: 1) evaluation of the influence on rooting of K-IBA and of different concentrations of SSHB; and 2) evaluation of the simultaneous use of K-IBA and two concentrations of SSHB on adventitious root formation. Samples were also collected for chemical studies. Results obtained in both studies confirmed the positive effect of K-IBA on the rooting percentage and on the number of adventitious roots produced. Furthermore, SSHB had a positive influence on the formation of lateral roots; the response was genotype and treatment dependent. Soluble sugars and phenol composition at the rooted cutting base was differentially influenced by the genotype and the growth regulators used.