The effect of irrigation on fruit development of olive cultivars 'Frantoio' and 'Leccino'

A field study was conducted on mature trees of two olive cultivars (`Frantoio' and `Leccino') in Tuscany (Italy) to assess differences between irrigated and rainfed trees in fruit growth parameters and the cellular processes determining mesocarp growth. Reference evapotranspiration, calculated by the Penman-FAO equation, was multiplied by a crop coefficient of 0.55 or 0.65 to determine the amount of irrigation water. The fresh weight and dry weight of fruits and their tissues were monitored at approximate two-week intervals. At 9 (end of massive endocarp sclerification) and 20 weeks after full bloom (AFB) fruit anatomical parameters were measured in transverse equatorial sections using image analysis. Fruits from irrigated trees showed greater equatorial diameter and mesocarp transverse area than those from rainfed trees of both cultivars at 9 and 20 weeks AFB. Irrigation significantly increased the size of mesocarp cells of both cultivars at 9 and 20 weeks AFB, and cell number in `Leccino' at 9 weeks AFB.