The effect of different irrigation levels on the oleuropein contents of olive tree (<i>Olea europaea</i> L. cv. Memecik) in the western coastal region of Turkey

Abstract

In this study, the effect of different irrigation levels on oleuropein content of olive (Olea europaea L. cv. Memecik) was researched in the Aegean Region during the crop season of 2007. Six different irrigation water levels of drip irrigation were tested using class A pan evaporation technique [I₀ (kpc:0), I_0.25 (kpc:0.25), I_0.50 (kpc:0.50), I_0.75 (kpc:0.75), I_1.00 (kpc:1.00) and I_1.25 (kpc:1.25)]. Oleuropein contents of olive leaves were detected by high performance liquid chromatography (HPLC). Olive leaves showed considerable contents of oleuropein (16.25 ± 0.25%) collected from waterless regime applied trees during summer period. In the same regime, contents of oleuropein were decreased depending upon the increasing irrigation regimes: 0.25 (10.28 ± 0.13%); 0.50 (2.19 ± 0.12%); 0.75 (1.43 ± 0.03%); 1.00 (0.09 ± 0.05%), although in winter period, contents of oleuropein were approximately stable as 0.55 ± 0.01% in waterless regime (rain-fed olives), equal in 0.25 (0.25 ± 0.04%) and 0.50 (0.25 ± 0.01%), in 0.75 (0.21 ± 0.01%), 1.00 (0.16 ± 0.02%) and (0.14 ± 0.03%) in 1.25 irrigation regimes. Contents of oleuropein was observed to be increased inversely proportional with increased irrigation regimes in autumn period. The oleuropein values were 1.21 ± 0.01% in waterless, 0.76 ± 0.01% in 0.25 irrigation, 0.45 ± 0.03% in 0.50 irrigation, 0.44 ± 0.03% in 0.75 irrigation, 0.33 ± 0.01% in 1.00 irrigation and 0.25 ± 0.02% in 1.25 irrigation regimes. No important increase or decrease between contents of oleuropein depending upon the gradually increased irrigation regimes was observe in spring period [in waterless regime (0.51 ± 0.05%), 0.25 irrigation (0.39 ± 0.04%); 0.50 irrigation (0.38 ± 0.14%); 0.75 irrigation (0.11 ± 0.01%); 1.00 irrigation (0.55 ± 0.04%); and 1.25 irrigation (0.79 ± 0.06%)]. Statistically important increases in oleuropein contents were in inverse proportion with the exponential irrigation regimes.

Key words: Olea europaea L., olive leaves, oleuropein, irrigation, seasonal variation.