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, 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; 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 rooting percentage and on number of adventitious roots produced. Furthermore, SSHB had a positive influence on the formation of lateral roots; the response is genotype and treatment dependent. Soluble sugars and phenol composition at the rooted cutting base is differentially influenced by the genotype and the growth regulators used.