Assessment of the effect of different deficit irrigation strategies on polyphenolic compounds of olives (cv. “Cobrançosa”)

Olive tree (Olea europaea L.) is one of the most important fruit trees of Mediterranean countries due its food products, table olives and olive oil that are well known by its high biophenol contents. Different water regimes affect the general development and the composition of olive fruit [1] leading to slight changes in the taste of the resulting oil [2] Particular attention has been given to the changes in phenolic compounds. Although this is not a general effect and responses may differ in relation to the genotype, generally olives harvested from irrigated trees show a lower accumulation of total phenols [3]. Contrasting evidence has not completely clarified the relation between water availability and the oleuropein content in the drupes [4]. This study was undertaken to assess the effect of different deficit irrigation strategies on polyphenolic compounds of olives. Field trials took place in a typical olive growing area of Northeast Portugal region, Vilariça Valley (“Terra Quente Transmontana”), in 2013 year in an irrigated olive orchard with “Cobrançosa Transmontana” cultivar. Four irrigation regimes were applied: i) a well irrigated treatment (T1), that received a seasonal equivalent water amount to satisfied crop evapotranspiration (100%ETc), irrigated on the two sides; three deficit irrigation treatment: two sustained deficit irrigation treatment: ii) irrigated with 40% T1 on two side (SDI40) and iii) irrigated with 75% T1 on two side 75% (SDI75) and a four treatment iv) Partial Root Drying System (PRD100), irrigated with 100% of T1 on one side, switching every 15 days. Total content of polyphenols (TP) and ortho-diphenols decreased during maturation and were affected by irrigation treatment (p