A regulated deficit irrigation strategy for hedgerow olive orchards with high plant density

Background & Aims There is not a consensus on the best irrigation approach for super-high density (SHD) olive orchards. Our aim was to design and test a regulated deficit irrigation (RDI) strategy for a sustainable balance between water saving, tree vigour and oil production. Methods We tested our RDI strategy for 3 years in an ‘Arbequina’ orchard with 1,667 trees ha−1. Two levels of irrigation reduction were applied, 60RDI and 30RDI, scaled to replacing 60 % and 30 %, respectively, of the of irrigation needs (IN). We also had a full irrigation (FI) treatment as control, with IN totalling 4,701 m3 ha−1 Results The 30RDI treatment showed the best balance between water saving, tree vigour and oil production. With a yearly irrigation amount (IA) of 1,366 m3 ha−1, which meant 72 % water saving as compared to FI, the reduction in oil yield was 26 % only. Conclusions Our results, together with recent knowledge on the effect of water stress on fruit development, allowed us to suggest a potentially improved RDI strategy for which a total IA of ca. 2,100 m3 ha−1 was calculated. Both some management details and the benefits of this suggested RDI strategy are still to be tested

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

Effects of tetraploidy on olive floral and fruit biology

Floral biology and fruit development were studied in Leccino Compact (LC), a polyploid olive mutant of cultivar Leccino (L). This mutant, considered a mixoploid with both diploid and tetraploid cells, has thicker leaves and fruit size similar to the diploid cultivar. So far, no information is available on its floral biology. In this study,the ploidy level ofthe LC fruit epicarp, analyzed by flow cytometry, was determined to be tetraploid. Pollen size distribution confirmed that most flowers were tetraploid. Morphological and histological measurements of various floral structures and fruits were carried out on the two genotypes, and LC showed larger floral structures (i.e. rachis, flower and ovary) and slightly higher pistil abortion rates. The total number of flowers per inflorescence was not significantly different between L and LC. The large difference (about 2 fold) in ovary cross sectional area between LC and L ovaries was mainly due to increased cell size. LC had slightly larger fruit cross-sectional area (but not greater fruit volume, since LC fruits were less elongated), with much larger cells. Therefore tetraploidy resulted in larger floral structures, as normally occurs in tetraploid plants, but had little effect on fruit size, despite much larger cell size