Advances in olive fruit cell and tissue development

The physiology of fruit development is closely related to the cellular processes in the fruit tissues-cell division, expansion and differentiation. We have been carrying out microscopy and image analysis studies on olives to quantify these processes and provide a more comprehensive view of their role, timing, interaction, and the influencing factors. Ovary size and cell number at bloom are highly correlated with cultivar fruit size at maturity. The highest rate and amount of mesocarp cell division occurs immediately following bloom, and it continues throughout fruit development, although at a reduced rate. The differences in fruit size among cultivars are due to cell number and water status tends to impact cell size rather than number. Pit hardening requires the initiation and completion of individual cell sclerification, which is composed of a series of processes, which vary among cells but are coordinated for the endocarp tissue. Endocarp sclerification is affected by both water and assimilate availability, and it seems to drive the end of endocarp expansion rather than vice versa. These results provide new information for interpreting and managing olive fruit growth, and for choosing breeding criteria.