PRELIMINARY INVESTIGATION OF ENDOGENOUS GIBBERELLINS IN SEEDS OF OLIVE FRUITS (CV CORATINA)

A lack of flower bud formation during the “on” year is a common characteristic of most alternate-bearing species. Gibberellins (GAs) are generally found to strongly inhibit flowering, although the mechanism by which this occurs is not fully understood. The aim of this research was to identify GAs in olive seeds. The trials were carried out near Potenza in Southern Italy (41°03’ N, 15°42’ E) on irrigated olive trees (cv Coratina) planted in 1992. In 1997 olive trees in an “on” year were selected on the basis of similarity in vigour, potential crop load and preliminary leaf gas exchange measurements. Seed samples were collected at the pit hardening phase to identify GAs by GC-MS. Analyses were carried out at IACR-Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol. GA8, GA17, GA19, GA23, GA28, GA29, GA29-catabolite, GA34, and GA53 were identified in the seeds of olive trees. The presence of some of these GAs suggests that this species utilises the early C-13 hydroxylation GA biosynthetic pathway, as found in apple, sour cherry, and pea plants. These GAs have a high degree of hydroxylation. Many authors indicated that hydroxylation is necessary for the movement of GAs in the tissue where fruit bud induction occurs. Furthermore, the negative effect of GAs on floral induction increases with the increasing degree of hydroxylation.