Bruising response in ‘Manzanilla de Sevilla’ olives to RDI strategies based on water potential

Abstract

Bruising is defined as the dark spots on the fruit surface that progress into the mesocarp as a consequence of mechanical damage during harvesting, handling or transport. Bruising is a relevant table olive quality trait since it may cause consumer rejection. In the last decades, olive orchards which were traditionally rainfed are being irrigated in order to increase productivity. However, currently Regulated Deficit Irrigation (RDI) strategies have been implanted in oil olive and recently in table olive orchards. Appropriate RDI strategies reduce total water consumption with little or no effect on production or fruit quality. In this work, the effect on bruise damage at harvest of three RDI treatments based on measurements of water potential during pit hardening compared to optimal plant water status (-1.2 MPa before pit hardening and -1.4 MPa after) has been studied in ‘Manzanilla de Sevilla’ olives. The strategies were as follows: RDI-1 aimed a moderate water stress at pit hardening (-2.0 MPa) and regular recovery at late August; RDI-2: severe water stress at pit hardening (-3.5 MPa) and early recovery (late July); RDI-3: severe water stress at pit hardening (-3.5 MPa) and regular recovery. This study was performed throughout the fruit growing season. The treatment with the highest Stress Integral (RDI-3) reduced pulp-to-pit ratio (on fresh weight basis) with no effect on fruit weight or oil content and more than 90% of the fruits reaching commercial categories according to the size. Furthermore, this treatment reduced the size of fruit bruises in comparison to early rehydration strategy.