Immunolocalization and quantification of IAA after self- and free-pollination in Olea europaea L.

In order to characterise the self-compatibility in ‘Pisa 9’, that is an improved clone of cultivar Leccino (Olea europaea L.), biological, histological and biochemical analyses were carried out. Observations were also focused on ‘Pendolino’, the main pollinator for Italian cultivars considered as being self-incompatible. After self-pollination, in ‘Pisa 9’ the majority of the pollen tubes reached the distal part of the style, entered the ovule leading to a high fruit-set percentage. These same processes were also noted in the Pendolino cultivar, though in a lesser degree. The indole acetic acid (IAA) concentration and its immunocytochemical localization were determined in pollinated flowers after self- and free-pollination and in unpollinated flowers. In both cultivars the highest IAA levels and signal intensity were observed in free-pollinated pistils, whereas after self-pollination a different behaviour emerged. In ‘Pendolino’ the immunostaining was not uniformly distributed and stopped at the style level. This finding sustained the low percentage of fruit-set obtained in the cultivar. In ‘Pisa 9’ the auxin distribution was similar to the free-pollinated pistils where the immunolocalization staining reached the ovary. The correspondence between the IAA signal in the ovary and the high percentage of fruit-set in ‘Pisa 9’ self-pollinated pistils, confirms the role of this hormone in the induction and regulation of the fertilisation process.