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Bruising response in ‘Manzanilla de Sevilla’ olives to RDI strategies based on water potential
Agricultural Water Management 222 (2019) 265–273
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Bruising response in ‘Manzanilla de Sevilla’ olives to RDI strategies based on water potential
T
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L. Casanovaa, , M. Corella,b, M.P. Suáreza, P. Ralloa, M.J. Martín-Palomoa,b, A. Morales-Silleroa, A. Morianaa,b, M.R. Jiméneza a Departamento de Ciencias Agroforestales. Escuela Técnica Superior de Ingeniería Agronómica, ETSIA, Universidad de Sevilla, Ctra. de Utrera s/n, Km 1, Sevilla, 41013, Spain b Unidad Asociada al CSIC de Uso sostenible del suelo y el agua en la agricultura (US-IRNAS), Ctra. de Utrera Km 1, 41013, Sevilla, Spain
A R T I C LE I N FO
A B S T R A C T
Keywords: Table olive Fruit damage Cuticle Pit hardening Stem water potential (SWP) Stress integral
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.
1. Introduction The olive tree (Olea europaea L.) has been traditionally rainfed, but intensification and productivity increase have favored its transformation to an irrigate crop in the last decades. At present, water scarcity in arid and semi-arid regions such as Spain has expanded the irrigation programming technique called Regulated Deficit Irrigation (RDI). This irrigation programming is based on the existence of plant phenological stages that are more water stress resistant during which the water applied may be reduced without significantly affecting the yield or the fruit quality (Behboudian and Mills, 1997). RDI was developed at the beginning of the 80’s in peach (Chalmers et al., 1981) whereas the use of RDI in olive orchards was firstly described by Goldhamer (1999) at the end of the 90’s. Nowadays, RDI strategies have been implanted in oil olive plantations (Lavee et al., 2007; Iniesta et al., 2009; Fernández et al., 2013; Gómez del Campo et al., 2014; Carrillo et al., 2018) and recently in table olive orchards (Correa-Tedesco et al., 2010; Corell
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et al., 2018). In olive, pit hardening has been commonly reported as the most resistant phenological stage (Goldhamer, 1999; Moriana et al., 2003; Iniesta et al., 2009). Moriana et al. (2012) proposed the use of stem water potential (SWP) thresholds measured at mid-day to maintain an adequate water status: -1.2 MPa for the flowering-fruit set phase and -1.4 MPa for the massive pit hardening phase in ‘Manzanilla de Sevilla’. However, the level of water stress at pit hardening may be higher without affecting the harvest, with an adequate rehydration (Moriana et al., 2003; Iniesta et al., 2009). A water stress of -2.0 MPa would not affect the fruit development (Dell’Amico et al., 2012), although a reduction of fruit size could occur if the deficit period is too long (Girón et al., 2015). Values below -3.5 MPa reduced current season productivity in cv Arbequina (Marra et al., 2016). Rehydration during the last part of the fruit growth period, once pit hardening is finished, resumes the growth of the olive fruit so that no differences are found at harvest (Girón et al., 2015).
Corresponding author. E-mail address: [email protected] (L. Casanova).
https://doi.org/10.1016/j.agwat.2019.06.007 Received 2 February 2019; Received in revised form 30 April 2019; Accepted 6 June 2019 Available online 14 June 2019 0378-3774/ © 2019 Elsevier B.V. All rights reserved.
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(RDI) strategies based on water status measurements, with stem water potential measure. The irrigation treatments were a control and three RDI (Table 1). Control treatment consisted in optimal plant water status (-1.2 MPa before the beginning of pit hardening and recovery (-1.4 MPa) until harvest. RDI-1 was -1.2 MPa before the beginning of pit hardening and a moderate water stress (-2 MPa) from the beginning of pit hardening until late August (August 29th, 2017; DOY 241; DAFB 136) and then the fruit was rehydrated (-1.4 MPa) until harvest (regular recovery); RDI-2 was -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late July (July 26th, 2017; DOY 206; DAFB 101) and then the fruit was rehydrated (-1.4 MPa) until harvest (early recovery); and RDI-3 was -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated (-1.4 MPa) until harvest (regular recovery). The beginning of the pit hardening period was considered as the moment when the rate of longitudinal fruit growth decreased (Rapoport et al., 2013). The experimental layout was a randomized design with four blocks and 12 trees per plot, arranged in three lines. The two central trees were measured and all adjacent trees were guard trees. Fruits were hand harvested at three different sampling dates: beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58), beginning of regular recovery (August 29th, 2017; DOY 241; DAFB 136), and the last date coinciding with harvest (September 19th, 2017; DOY 262; DAFB 157) in the ripening stage for green processing (Maturity Index = 1, Ferreira (1979)). For each treatment, replicate and sampling date the effect of RDI was quantified by several parameters: fruit weight (g), fruit volume (mL), fruit moisture (%), pulp-to-pit ratio (on fresh and dry weight basis), firmness (kg) and oil content (% on dry weight). Fruit weight (g) and the pulp-to-pit ratio (on fresh basis) were determined in subsamples of 0.5 kg of fruits. The pulp-to-pit ratio was determined in fresh weight as the difference between fruit and pit weights. Fruits were dried at 105 °C for 48 h to stable weight, and moisture content (%) and the pulpto-pit ratio on dry weight basis were determined. Oil content was also estimated by a NMR analyser Minispec NMS100 (Bruker Optik GmbH, Ettlingen, Germany) according to Del Río and Romero (1999) using 100 fruits. Fruit volume (mL) was measured from the volume of water displaced on immersion of 100 fruits in a graduated beaker with water. Firmness (kg) of table olives was measured in a subsample of 30 fruits using a fruit pressure tester called Penetrometer (Model FT 327 (3–27 Lbs.)), with a strut of 2 mm of diameter attached at the tip. The strut was slowly introduced in each fruit assessing its firmness. At harvest, fruit size distribution (fruits kg−1) was also calculated. Midday stem water potential (SWP) was measured weekly in one leaf per tree with the pressure chamber (Model 1000, PMS, USA) using the Scholander et al. (1965) technique from March 30th, 2017 (DOY 89) until September 19th, 2017 (DOY 262; DAFB 157) and it was used to characterize the water status of trees for each treatment. The leaves near the main trunk were covered in aluminum foil at least two hours before measurements were taken. In order to describe the accumulative effect of the water deficit, the water Stress Integral (SI) was calculated from the Ψ data (Myers, 1988) during the period of water stress (Eq. (1)). Eq. (1) used a reference of -1.4 MPa. The expression used was:
The effect of RDI strategies on olive oil quality has been long studied by different authors (Patumi et al., 2002; Sena‐Moreno et al., 2017; Ahumada et al., 2018), whereas there is very little information concerning the effect of RDI strategies on table olive fruit quality which has not been considered until recently (Cano-Lamadrid et al., 2015; Casanova et al., 2017). Fruit appearance is key for table olives since any defect on the surface of the fruit may cause consumer rejection and may reduce its market value. Thus, the absence of bruises is a relevant table olive quality trait (Rallo et al., 2018). Bruising is the most common mechanical damage of the olive fruit, usually occurring during harvesting and characterized by the formation of more or less extensive superficial browning injuries (Gambella et al., 2013; Jiménez et al., 2017) and cell damage (cell rupture and loss of cell wall thickness) extended into the mesocarp. Bruising is influenced by preharvest and postharvest factors such as the cultivar (Jiménez-Jiménez et al., 2013; Jiménez et al., 2016), the irrigation regime (Cano-Lamadrid et al., 2015; Casanova et al., 2017) or the mechanization of harvesting (Morales-Sillero et al., 2014). Nowadays, bruise susceptibility is the main limitation to table olive mechanical harvesting (Morales-Sillero et al., 2014). ‘Manzanilla de Sevilla’ is one of the most important table olive cultivars worldwide but it is more susceptible to bruising than other table olive varieties like ‘Hojiblanca’ (Jiménez-Jiménez et al., 2013; Jiménez et al., 2016) or ‘Manzanilla Cacereña’ (Morales-Sillero et al., 2014; Jiménez et al., 2017). Differences in bruise susceptibility seems to be a function of several physico-mechanical properties such as size, pulp to pit ratio, water status, fruit firmness and fruit structural traits as cuticle thickness (Hammami and Rapoport, 2012; Jiménez-Jiménez et al., 2013; Jiménez et al., 2017). Concerning water status, Casanova et al. (2017) studied the effect of water stress in the sensitive crop phase (-1.2 MPa before pit hardening and withholding until -2.5 MPa four weeks before harvest without recovery) on bruising. They found that a moderate water deficit entails a reduction of 50% of irrigation water without affecting fruit weight, volume or pulp-to-pit ratio (on fresh and dry weight basis) in Manzanilla de Sevilla cv. and improves fruit resistance to bruising, as evidenced by the lower bruising index and the lower external and internal damaged area. 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 has been studied in the same cultivar. Several fruit quality traits have also been determined, namely weight (g), size (fruit kg−1), moisture content (%), pulp-to-pit ratio (on fresh and dry weight basis), and oil content (% dry weight), as well as important anatomical features related to the cuticle and the epidermis. 2. Material and methods 2.1. Plant material and location of trial Fruits of thirty years old ‘Manzanilla de Sevilla’ table olive trees were evaluated in this study throughout the fruit growing season of the 2017 year. Trees were cultivated in a commercial orchard in Dos Hermanas (Seville, Southern Spain, 37°15′00″N, 5°56′54″O and 42 m altitude, ETRS 89) in a standard layout of 7 m by 4 m (357 trees ha−1), under an irrigation system in a well-established olive grove in full production. The full flowering was on April 15th, 2017 (Day of year (DOY) 105), the beginning of pit hardening was on June 12th, 2017 (DOY 163, Days after full bloom (DAFB) 58) and the harvest was on September 19th, 2017 (DOY 262, DAFB 157). Climatic conditions occurred along the experimental year are presented in Fig. 1.
SI = |∑(Ψ-(-1.4))|∗n
(1)
Where: SI is the stress integral, Ψ is the average midday stem water potential for any interval, and n is the number of the days in the interval. Linear regression between Stress Integral and fruit moisture was determined.
2.2. Experiment design and measurements Table olive trees were evaluated under regulated deficit irrigation 266
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Fig. 1. a. Seasonal daily reference Evapotraspiration (circles) and Rain (bars). b. Seasonal daily maximum air temperature (circles) and maximum vapor pressure deficit (VPD) (triangles). Table 1 Irrigation treatments: Control and Regulated Deficit Irrigation (RDI) strategies based on water status measurements. Midday stem water potential (SWP) thresholds Beginning of pit hardening June 12th, 2017 (DOY 163, DAFB 58) Treatment
Before
After
Recovery
Control RDI-1 RDI-2 RDI-3
−1.2 MPa −1.2 MPa −1.2 MPa −1.2 MPa
−1.4 MPa −2.0 MPa −3.5 MPa −3.5 MPa
Regular recovery: August 29th, 2017 (DOY 241; DAFB 136) Early recovery: July 26th, 2017 (DOY 206; DAFB 101) Regular recovery: August 29th, 2017 (DOY 241; DAFB 136)
DOY: Day of year; DAFB: Days after full bloom.
fruits was bruise-induced by letting them fall from one meter high according to methodology proposed by Jiménez et al., 2016. The percentage of bruised fruits (%) and the bruise index were also quantified three hours after the impact, and then fixed in a FAE solution (formalin, acetic acid, 95% ethanol and distilled water (10:5:50:35 v/v/v/v) (Berlyn and Miksche, 1976). External bruise area and volume were quantified according to the methodology by Morales-Sillero et al. (2014) in 30 damaged fruits (bruise-induced) per treatment and
2.3. Bruising measurements At harvest time, a sample of about 2.5 kg of fruits was taken for each treatment and replicate. Later, a subsample of one hundred fruits per treatment and replicate was selected and the percentage of bruised fruits (%) and the bruise index (0 (no bruising) to 2 (severe bruising)) were quantified at 3 h after harvest according to Morales-Sillero et al. (2014). Furthermore, another subsample of one hundred undamaged 267
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replicate. Previously, to eliminate FAE solution, about three weeks after, the subsamples were introduced in ethanol 70% solution. Ten damaged fruits per treatment and replicate were rehydrated according to Gucci et al. (2009), to quantify Internal Damage Area (mm2). Damaged mesocarp portions were obtained and evaluated according to the methodology described by Jiménez et al. (2016). Internal Damage Area (mm2) was quantified in photographic images taken with a Nikon Digital camera (Sight DS Ri 1) connected to a binocular loupe Nikon (Nikon, SMZ 1270, Tokyo, Japan) and analyzed with Nis-Elements AR 3.2 image analysis software. 2.4. Characterization of the cuticle and epidermis features For each treatment, replicate and sampling date, the cuticle and epidermal cell features were also quantified in mesocarp portions after a histological process described by Jiménez et al. (2016). First, ten undamaged fruit mesocarp portions were subjected to a process of dehydration (Berlyn and Miksche, 1976) and then were embedded in Histosec® embedding paraffin at a melting point of 56–58 °C (Merck, Darmstadt, Germany). Secondly, transverse sections of 12 μm thick were obtained with a rotary microtome (Reichert Histostat 820, Buffalo, USA). These histological sections were mounted on glass slides and stained with 0.05% toluidine blue for 60 min prior to paraffin removal (Sakai, 1973). Later, photographic images of all sections were taken with a Nikon Digital camera (Sight DS Ri 1) connected to a binocular loupe Nikon (Nikon, SMZ 1270, Tokyo, Japan) and with processed NisElements AR 3.2 image analysis software. Ten histological sections per treatment, replicate and date from undamaged fruits were used to assess the cuticle and epidermis features. In each histological section, three different random zones composed of ten consecutive cells were used. According to the methodology proposed by Hammami and Rapoport (2012), the combined epidermal area (Ar Ep, μm2) and length (L Ep, μm) of each cell group and the combined cuticle area (Ar Cu, μm2) were quantified. Then, the cuticle thickness (μm), cuticle area/cell (μm2), and both the epidermal cell radial (μm) and epidermal cell tangential widths (μm) were calculated as follows:
Cuticle thickness (μm) =
Cuticle area/cell(μm2) =
Fig. 2. Pattern of midday stem water potential along the experiment during 2017 season. Each point is the average of 4 data. Vertical bars represented standard error. First vertical line shows the beginning of pit hardening period, second show early recovery and third regular recovery. Stars indicates dates where statistical differences were significant (*P < 0.05; +P < 0.01, Tukey Test). Control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58) and -1.4 MPa until harvest (September 19th, 2017; DOY 262; DAFB 157). RDI-1: -1.2 MPa before the beginning of pit hardening and a moderate water stress (-2.0 MPa) from the beginning of pit hardening until late August (August 29th, 2017; DOY 241; DAFB 136) and then the fruit was rehydrated until harvest (regular recovery); RDI-2: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late July (July 26th, 2017; DOY 206; DAFB 101) and then the fruit was rehydrated until harvest (early recovery); RDI-3: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery). DOY: Day of year; DAFB: Days after full bloom.
treatment reached SWP of -1.48 MPa before pit hardening and -2.16 MPa afterwards, slightly lower than the theoretical defined water potential. RDI-1 treatment consisted in a moderate water stress during pit hardening; before pit hardening water potentials were similar to control (-1.63 MPa) and at the end of water stress period and before the beginning of regular recovery (DOY 241), minimum values of SWP were lower than the control (-3.08 MPa) due to a problem in the irrigation system, but they were completely recovered (around -1.40 MPa) at the end of the experiment (DOY 262). RDI-2 treatment consisted in a shorter period of water stress at pit hardening; before the beginning of pit hardening minimum SWP was near to control and the early recovery at late July (DOY 206) recuperated plant water status (-2.44 MPa) until the theorical level considered and no differences were found with control treatment (-2.16 MPa). RDI-3 treatment consisted in a severe water stress at pit hardening; as in the rest of treatments, no water stress was obtained before pit hardening (-1.58 MPa) and minimum SWP during the period of stress and recovery were reached before the beginning of the regular recovery (DOY 241), showing severe water stress conditions (-3.69 MPa) at DOY 220. In summary, SWP was similar in the four treatments before pit hardening (above -1.5 MPa). Later, SWP in all treatments decreased reaching values slightly below -2 MPa until late July (DOY 206), when water status of the different irrigation treatments began to differentiate. Statistically significant differences for SWP among irrigation treatments were observed at the beginning of the regular recovery period (DOY 241), especially between RDI-3 and the other treatments, though at harvest all trees showed similar values to the control (around -1.40 MPa) (Fig. 2). Taking into account the water relations (Table 2) and fruit quality
Ar Cu L Ep
Ar Cu 10
Epidermal cell radial width (μm) =
Ar Ep L Ep
Epidermal cell tangential width (μm)=
L Ep 10
2.5. Statistical analysis Data were analyzed with StatGraphics Plus V. 5.1 (Manugistics Inc., USA) by ANOVA to determine the effect of water stress treatments on fruit traits. The Tukey’s test (P < 0.05) was used to discriminate among the mean values. When necessary, data were previously transformed using Box-Cox power transformations (Box and Cox, 1964) to achieve normality and homogenize the variance. A linear regression between Stress Integral (SI, MPa day) and fruit moisture was also calculated. 3. Results and discussion RDI treatments in this work were theoretically defined to reach certain levels of water stress as explained in material and methods section, but the real pattern of midday stem water potential (SWP) reached during the irrigation season is shown in Fig. 2. Control 268
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among treatments, neither for minimum SWP (Fig. 2). Fruit quality traits as weight, volume, moisture, pulp-to-pit ratio (on fresh and dry basis), and oil content (% dry weight) showed no differences between RDI treatments and control at this phenological stage (Table 3). Statistical differences were found in firmness among treatments, but later they disappeared. Until late August (after early recovery and at the beginning of regular recovery) (DOY 89-241), there were significant differences in the minimum SWP and Stress Integral especially between RDI-3 and the other treatments (Fig. 2 and Table 2); RDI-1 induced a moderate water stress and since early recovery of RDI-2 treatment had already taken place (DOY 206), none of those treatments differed significantly from the control (-2.16 MPa). In fact, RDI-2 (early recovery of punctual water stress) was the less stressed RDI treatment (48.29 MPa day), without significant differences with respect to control and the regular recovery of moderate water stress treatment RDI-1 (64.08 MPa day) and severe water stress treatment RDI-3 (89.06 MPa day) was significantly the most stressed treatment. For RDI-3 the regular recovery was slower, thus the minimum SWP in this phase reached the lowest value (-3.69 MPa) (Fig. 2) and fruit weight, volume, moisture and pulp-to-pit ratio (on fresh and dry basis) decreased in this treatment with respect to the others treatments, but only significantly with respect to RDI-2 (Table 3). In addition, this treatment wasted less amount of water, and was the only treatment that significantly reduced total water applied with respect to the control treatment at harvesting (105 vs 274 mm, respectively) (Table 2). No differences among treatments were found in flesh firmness nor oil content at this period (Table 3). At harvest (DOY 262), none of the RDI treatments had effect on fruit weight (ranged between 4.01 and 4.60 g), volume (ranged between 4.00 and 4.71 mL), pulp-to-pit ratio on dry basis (ranged between 2.25 and 2.50), firmness (ranged between 1.09 and 1.17 kg) or oil content (38.90 and 41.66%) (Table 3) because regular (late August) or early (late July) recovery reduced water stress of the fruits before harvest, as Girón et al. (2015) observed. However, the pulp-to-pit ratio on fresh weight basis was significantly different between RDI-2 and RDI-3 (7.70 and 6.37, respectively) (Table 3). Furthermore, although RDI treatments didn’t significantly modify mean fruit weight, the number of fruit kg−1 was increased in RDI-3 (Fig. 3). Such effect was likely related with irrigation scheduling because the yield of the trees were very similar (Table 2). This was probably related to fruit moisture which linearly decreased with increasing Stress Integral (R2 = 0.6381) (Fig. 4), and the RDI-3 fruits showed the lowest values (62.98%) with respect to the
Table 2 Yield (kg tree−1) at harvest and cumulative values of Applied water (mm) and Stress Integral (MPa day) from March 30th, 2017 (DOY 89) until the beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58), until the beginning of early recovery (July 26th, 2017; DOY 206; DAFB 101), until the beginning of regular recovery (August 29th, 2017; DOY 241; DAFB 136) and until harvest (September 19th, 2017; DOY 262; DAFB 157). Weekly measurements. Cumulated period until
Treatment
Beginning of pit hardening
Control RDI-1 RDI-2 RDI-3 Control RDI-1 RDI-2 RDI-3 Control RDI-1 RDI-2 RDI-3 Control RDI-1 RDI-2 RDI-3
Beginning of early recovery Beginning of regular recovery Harvest
Yield (kg tree−1)
Applied water (mm)
Stress Integral (MPa day)
34.2 26.6 38.7 29.5
19 ± 7 33 ± 22 19 ± 11 23 ± 14 31 ± 5 45 ± 29 19 ± 11 23 ± 14 247 ± 40 b 172 ± 26 ab 301 ± 95 b 32 ± 15 a 274 ± 35 b 295 ± 39 b 360 ± 52 b 105 ± 14 a
1.98 ± 1.61 3.31 ± 2.53 2.78 ± 1.56 4.22 ± 1.68 17.15 ± 5.44 a 29.04 ± 9.79 ab 30.75 ± 8.68 ab 32.76 ± 8.07 b 31.34 ± 11.20 a 64.08 ± 17.38 b 48.29 ± 13.12 ab 89.06 ± 28.17 b 33.70 ± 6.69 a 70.69 ± 9.74 ab 51.27 ± 6.93 a 97.9 ± 15.39 b
± ± ± ±
5.6 3.1 1.4 3.9
Different letters indicate significant differences among treatments according to the Tukey Test (P < 0.05) for each parameter and date. Control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening and -1.4 MPa until harvest. RDI-1: -1.2 MPa before the beginning of pit hardening and a moderate water stress (-2.0 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery); RDI-2: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late July and then the fruit was rehydrated until harvest (early recovery); RDI-3: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery). DOY: Day of year; DAFB: Days after full bloom.
(Table 3) we can describe the effect of water stress in different phenological stages. At the beginning of the studied period (DOY 89-163), before the beginning of pit hardening, the Stress Integral ranged from 1.98 (Control) to 4.22 MPa day (RDI-3) without significant differences
Table 3 Effect of RDI treatments on fruit traits in three moments: beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58), beginning of regular recovery (August 29th, 2017; DOY 241; DAFB 136) and at harvest (September 19th, 2017; DOY 262; DAFB 157). Date
Treatment
Fruit Weight (g)
Fruit Volume (ml)
Fruit Moisture (%)
Pulp-to-pit ratio (on fresh weight basis)
Pulp-to-pit ratio (on dry weight basis)
Firmness (kg)
Beginning of pit hardening
Control RDI-1 RDI-2 RDI-3 Control RDI-1 RDI-2 RDI-3 Control RDI-1 RDI-2 RDI-3
1.78 1.85 1.81 1.81 3.67 3.47 3.86 3.16 4.42 4.40 4.60 4.01
1.63 1.54 1.50 1.63 3.62 3.50 3.87 3.00 4.33 4.25 4.71 4.00
63.31 62.83 62.30 62.45 66.28 63.62 65.51 59.23 67.09 65.75 66.96 62.98
1.88 2.00 1.87 1.87 4.85 4.85 5.67 3.86 6.99 6.92 7.70 6.37
0.86 0.86 0.83 0.82 1.77 1.93 1.92 1.73 2.30 2.50 2.45 2.25
1.86 1.77 1.66 1.77 1.61 1.65 1.55 1.67 1.17 1.12 1.09 1.14
Beginning of regular recovery
Harvest
± ± ± ± ± ± ± ± ± ± ± ±
0.10 0.20 0.06 0.09 0.39 0.26 0.39 0.19 0.52 0.50 0.34 0.11
ab ab b a
± ± ± ± ± ± ± ± ± ± ± ±
0.08 0.16 0.14 0.08 0.48 0.45 0.31 0.24 0.54 0.57 0.39 0.49
ab ab b a
± ± ± ± ± ± ± ± ± ± ± ±
0.66 1.07 0.39 0.16 0.71 1.01 0.84 5.51 0.66 0.26 0.73 0.71
b ab b a c b bc a
± ± ± ± ± ± ± ± ± ± ± ±
0.10 0.08 0.11 0.11 0.33 0.36 1.20 0.46 0.50 0.81 0.47 0.34
ab ab b a ab ab b a
± ± ± ± ± ± ± ± ± ± ± ±
0.11 0.04 0.04 0.11 0.13 0.11 0.02 0.02 0.12 0.12 0.14 0.11
ab b b a
± ± ± ± ± ± ± ± ± ± ± ±
0.09 0.06 0.03 0.06 0.14 0.13 0.09 0.06 0.13 0.10 0.10 0.04
Oil content (% dry weight)
b ab a ab
0.69 ± 0.65 0.72 ± 0.40 0.48 ± 0.34 0.94 ± 0.68 31.71 ± 1.20 32.13 ± 2.44 34.63 ± 3.52 34.20 ± 1.01 39.38 ± 0.98 40.69 ± 1.92 38.90 ± 2.80 41.66 ± 0.95
Different letters indicate significant differences among treatments according to the Tukey Test (P < 0.05) for each parameter and date. Control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening and -1.4 MPa until harvest. RDI-1: -1.2 MPa before the beginning of pit hardening and a moderate water stress (-2.0 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery); RDI-2: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late July (July 26th, 2017; DOY 206; DAFB 101) and then the fruit was rehydrated until harvest (early recovery); RDI-3: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery). DOY: Day of year; DAFB: Days after full bloom. 269
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Fig. 3. Fruit size distribution at harvest in RDI and control treatments. Control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58) and -1.4 MPa until harvest (September 19th, 2017; DOY 262; DAFB 157). RDI-1: -1.2 MPa before the beginning of pit hardening and a moderate water stress (-2.0 MPa) from the beginning of pit hardening until late August (August 29th, 2017; DOY 241; DAFB 136) and then the fruit was rehydrated until harvest (regular recovery); RDI-2: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late July (July 26th, 2017; DOY 206; DAFB 101) and then the fruit was rehydrated until harvest (early recovery); RDI-3: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery). DOY: Day of year; DAFB: Days after full bloom.
RDI treatments neither affected bruised fruits (ranging between 24.28% for RDI-3 and 28.28 for RDI-2) nor bruise index (ranged between 0.24 for RDI-3 and 0.28 for RDI-2), when fruits were hand harvested (Table 4). After an induced impact, the percentage of bruised fruits and bruise index increased to 94% and 1.0 approximately, without differences among RDI treatments and control. When fruits were hand harvested all bruised fruits were classified as low-damaged, but when fruits were bruise induced, the percentage of severe-damage ranged between 4.51 for RDI-1 and 9.29 for RDI-2 without significant differences among RDI treatments in any case. Similar bruising values were observed by Jiménez et al. (2011) for ‘Manzanilla de Sevilla’ fruits after an induced impact. Nevertheless, external damaged area and bruise volume decreased significantly in the most water stressed fruits (RDI-3) (36.02 mm2 and 66.83 mm3, respectively), compared to the early recovery treatment (RDI-2) (43.27 mm2 and 96.85 mm3, respectively) that finally received the same applied water as the control (Table 2). These results are in agreement with Casanova et al. (2017) who studied the effect of RDI in the sensitive crop phase (-1.2 MPa before pit hardening and withholding until -2.5 MPa four weeks before harvest without recovery). With respect to the internal damage, an evident discoloration through the mesocarp was observed in the bruised mesocarp sections. The discoloration was surrounded by a darker halo
Fig. 4. Linear regression between Stress Integral (SI, MPa day) and fruit moisture (%) at harvest.
control fruits (67.09%) (Table 3). Despite this, 93.75% of the fruits from RDI-3 were classified within commercial categories (< 340-360 fruits kg-1) according to the Spanish trade standard regulation for table olives cv. Manzanilla de Sevilla (Orden CAPDR, 49066/, 2018). These results suggested that the recovery period could compensate severe water stress level as in RDI-1. Such level of water stress is similar to the ones suggested by Girón et al. (2015). Table 4 Effect of RDI treatments on fruit bruising at harvest. Treatment
Manual Harvesting
Induced Impact
Total bruised fruits (%) No bruised fruits (%) Fruits with low damage (%) Fruits with severe damage (%) Bruise Index Total bruised fruits (%) No bruised fruits (%) Fruits with low damage (%) Fruits with severe damage (%) Bruise Index Internal Damaged Area (mm2) External Damaged Area (mm2) Bruise Volume (mm3)
Control
RDI-1
RDI-2
RDI-3
26.45 ± 4.44 73.55 ± 4.44 26.45 ± 4.44 0.00 ± 0.00 0.26 ± 0.04 94.66 ± 2.30 5.34 ± 2.30 89.81 ± 3.08 4.85 ± 3.14 0.99 ± 0.05 15.51 ± 1.22 40.49 ± 3.78 ab 91.50 ± 18.37 ab
26.25 ± 6.13 73.75 ± 6.13 26.25 ± 6.13 0.00 ± 0.00 0.26 ± 0.06 93.99 ± 3.91 6.01 ± 3.91 89.47 ± 2.07 4.51 ± 1.93 0.98 ± 0.06 14.37 ± 1.75 43.46 ± 0.75 b 95.47 ± 10.89 ab
28.28 ± 4.85 71.71 ± 4.85 28.04 ± 4.43 0.25 ± 0.49 0.28 ± 0.06 94.17 ± 3.08 5.82 ± 3.08 84.88 ± 2.38 9.29 ± 3.55 1.03 ± 0.06 15.53 ± 2.68 43.27 ± 2.70 b 96.85 ± 10.87 b
24.28 ± 5.76 75.72 ± 5.76 24.02 ± 6.18 0.25 ± 0.51 0.24 ± 0.06 94.00 ± 4.22 5.99 ± 4.22 85.02 ± 6.83 8.98 ± 4.60 1.03 ± 0.06 15.64 ± 3.43 36.02 ± 3.12 a 66.83 ± 8.93 a
Different letters indicate significant differences among treatments according to the Tukey Test (P < 0.05) for each parameter. Control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58) and -1.4 MPa until harvest (September 19th, 2017; DOY 262; DAFB 157). RDI-1: -1.2 MPa before the beginning of pit hardening and a moderate water stress (-2.0 MPa) from the beginning of pit hardening until late August (August 29th, 2017; DOY 241; DAFB 136) and then the fruit was rehydrated until harvest (regular recovery); RDI-2: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late July (July 26th, 2017; DOY 206; DAFB 101) and then the fruit was rehydrated until harvest (early recovery); RDI-3: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery). DOY: Day of year; DAFB: Days after full bloom. 270
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Fig. 5. Mesocarp portions of ‘Manzanilla de Sevilla’ 3 h after bruise induction impact, and prior to the histological procedure: (A) Fixed tissue portions from control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58) and -1.4 MPa until harvest (September 19th, 2017; DOY 262; DAFB 157). (B) Fixed tissue portions from RDI-3 treatment (-1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August (August 29th, 2017; DOY 241; DAFB 136) and then the fruit was rehydrated until harvest (regular recovery)). DOY: Day of year; DAFB: Days after full bloom. Table 5 Effect of RDI treatments on cuticle and epidermal cell features in three moments: beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58), beginning of regular recovery (August 29th, 2017; DOY 241; DAFB 136) and at harvest (September 19th, 2017; DOY 262; DAFB 157). Cuticle
Beginning of pit hardening
Beginning of regular recovery
Harvest
Epidermal cell size
Treatment
Thickness (μm)
Area/cell (μm2)
Radial width (μm)
Tangential width (μm)
Area (μm2)
Control RDI-1 RDI-2 RDI-3 Control RDI-1 RDI-2 RDI-3 Control RDI-1 RDI-2 RDI-3
8.93 ± 2.75 8.38 ± 2.64 7.73 ± 1.54 8.64 ± 1.44 10.93 ± 1.05 12.11 ± 1.75 11.50 ± 1.46 11.87 ± 1.31 11.07 ± 1.59 11.30 ± 1.41 11.05 ± 1.26 12.05 ± 1.70
179.81 168.74 152.59 181.27 265.79 292.95 283.20 293.29 262.36 272.40 282.70 291.26
16.38 16.30 16.59 16.59 14.51 13.95 13.90 14.19 14.47 14.23 14.35 14.25
20.24 20.13 19.69 20.91 24.24 24.24 24.68 24.74 23.73 24.16 24.67 24.18
332.47 326.91 326.72 347.25 350.59 337.65 342.06 350.20 343.18 343.93 353.19 344.62
± ± ± ± ± ± ± ± ± ± ± ±
52.73 55.38 34.03 35.37 39.58 49.03 34.49 43.83 39.27 33.45 42.48 45.02
± ± ± ± ± ± ± ± ± ± ± ±
1.49 1.32 1.50 1.30 1.34 0.99 1.63 1.54 1.47 0.92 1.28 1.01
± ± ± ± ± ± ± ± ± ± ± ±
1.81 1.67 0.99 1.32 1.99 2.35 1.37 2.04 1.70 1.35 2.66 1.92
± ± ± ± ± ± ± ± ± ± ± ±
47.51 26.22 37.17 37.33 32.91 37.67 38.12 42.50 36.32 30.03 37.69 33.85
Different letters indicate significant differences between treatments according to the Tukey Test (P < 0.05) for each parameter and date. Control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening and -1.4 MPa until harvest. RDI-1: -1.2 MPa before the beginning of pit hardening and a moderate water stress (-2.0 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery); RDI-2: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late July (July 26th, 2017; DOY 206; DAFB 101) and then the fruit was rehydrated until harvest (early recovery); RDI-3: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery). DOY: Day of year; DAFB: Days after full bloom.
presented the greater epidermal cell radial width (14.47 μm) and regular recovery treatments (RDI-1 and RDI-3) the lowest (14.23 and 14.25 μm, respectively) (Table 5). In spite of not having found significant differences for cuticle properties, the significant lower bruise damage observed in the most stressed treatment (RDI-3), both in the external area and volume of damaged fruit, could be related to the higher values observed for cuticle thickness and cuticle area per cell in the fruits of this treatment (Fig. 6 and Table 5). It is known that ‘Manzanilla de Sevilla’ is a bruise susceptible cultivar (Jiménez-Jiménez et al., 2013; Jiménez et al., 2016) and fruits present a thinner cuticle compared to other table varieties like Hojiblanca or Manzanilla Cacereña (Hammami and Rapoport, 2012; Jiménez et al., 2017) which are considered less susceptible to bruising. In our trial, the more stressed deficit irrigation treatment (RDI-3) seems to cause an increase in the cuticle thickness, as observed by other authors in some water stress conditions (Gómez del Campo et al., 2014; Patumi et al., 2002), although further research should be performed to confirm it.
and showed tissue ruptures inside without affecting the epidermis as previously described by Jiménez et al. (2016) (Fig. 5). No significant differences were neither found in the Internal Damaged Area values, that ranged between 14.37 mm2 (RDI-1) and 15.64 mm2 (RDI-3) (Table 4) although qualitatively, the discoloration in the most water stressed fruits (RDI-3) was lower (Fig. 5). RDI treatments had no significant effect on the cuticle and epidermis parameters during the fruit growing season from the beginning of pit hardening to harvest (Table 5). Regarding cuticle, at the beginning of pit hardening, the thickness ranged between 7.73 μm (RDI-2) and 8.93 μm (control) and cuticle area per cell ranged between 152.59 μm2 (RDI-2) and 181, 27 μm2 (RDI-3). At late August (regular recovery date) RDI fruits showed, however, thicker cuticle and larger cuticle area per cell (12.11 μm and 292.95 μm2 for RDI-1; 11.50 μm and 283.20 μm2 for RDI-2; 11.87 μm and 293.29 μm2 for RDI-3) than the control (10.93 μm and 265.79 μm2), although not significant. At harvest, the most stressed fruits (RDI-3) presented greater cuticle thickness (12.05 μm) and cuticle area per cell (291.26 μm2) and control fruits showed the lowest values for the same traits (11.07 μm and 262.36 μm2, respectively), even though the differences were again not significant (Table 5 and Fig. 6). Concerning epidermal cell size, no statistical differences were found at any date. At harvest, the RDI-2 fruits showed the largest tangential width (24.67 μm) and area (353.19 μm2) followed by RDI-3 fruits (24.18 μm and 344.62 μm2), and control fruits the lowest (23.73 μm and 343.18 μm2, respectively). Instead, control fruits
4. Conclusions The RDI-3 strategy (-1.2 MPa before the beginning of pit hardening and a severe water stress (-3.5 MPa) from the beginning of pit hardening until late August (DOY 241, DAFB 136) after which the fruit was rehydrated up to harvest (regular recovery)) was the most stressing 271
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R and AGL2016-75794-C4-4-R. The authors wish to thank the editor and the anonymous reviewers for detailed and constructive comments on earlier versions of this article. References Ahumada, L., Ortega-Farias, S., Searles, P.S., 2018. Olive oil quality response to irrigation cut-off strategies in a super-high density orchard. Agric. Water Manag. 202, 81–88. Behboudian, M.H., Mills, T.M., 1997. Deficit irrigation in deciduous orchards. Hortic. Rev. 21, 105–131. Berlyn, G.P., Miksche, J.P., 1976. Botanical Microtechnique and Cytochemistry, 3rd ed. Iowa State University Press, Ames, Iowa, USA. Box, G.E.P., Cox, D.R., 1964. An analysis of transformations. J. R. Stat. Soc. Ser. B 26 (2), 211–252. Cano-Lamadrid, M., Girón, I.F., Pleite, R., Burló, F., Corell, M., Moriana, A., CarbonellBarrachina, A.A., 2015. Quality attributes of table olives as affected by regulated deficit irrigation. Food Sci. Biotechnol. 62, 19–26. Carrillo, T., Corell, M., Martin-Palomo, M.J., Andreu, L., Trigo, E., Moriana, A., 2018. Regulated deficit irrigation based on midday stem water potential. Application on Commercial Orchards. Book of Abstracts 6th International Conference on the Olive Tree and Olive Products. pp. 112. Casanova, L., Corell, M., Suárez, M.P., Rallo, P., Martín-Palomo, M.J., Jiménez, M.R., 2017. Bruising susceptibility of Manzanilla de Sevilla table olive cultivar under regulated Deficit Irrigation. Agric. Water Manag. 189, 1–4. Chalmers, D.J., Mitchell, P.D., VanHeek, L., 1981. Control of peach tree growth and productivity by regulated water supply, tree density and summer pruning. J. Am. Soc. Hortic. Sci. 106, 307–312. Corell, M., Martín-Palomo, M.J., Girón, I., Andreu, L., Torrecillas, A., Centeno, A., PérezLópez, D., Moriana, A., 2018. Regulated deficit irrigation scheduling in table olive based on measurements of water potential during pit hardening. 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Gucci, R., Lodolini, E.M., Rapoport, H.F., 2009. Water deficit-induced changes in mesocarp cellular processes and the relationship between mesocarp and endocarp during olive fruit development. Tree Physiol. 29, 1575–1585. Hammami, S.B.M., Rapoport, H.F., 2012. Quantitative analysis of cell organization in the external region of the olive fruit. Int. J. Plant Sci. 173 (9), 993–1004. Iniesta, F., Testi, L., Orgaz, F., Villalobos, F.J., 2009. The effects of regulated and continuous deficit irrigation on the water use, oil and yield of olive trees. Eur. J. Agron. 30, 258–265. Jiménez, M.R., Casanova, L., Suárez, M.P., Rallo, P., Morales-Sillero, A., 2017. Internal fruit damage in table olive cultivars under superhigh-density hedgerows. Postharvest Biol. Technol. 132, 130–137. Jiménez, M.R., Rallo, P., Rapoport, H.F., Suárez, M.P., 2016. Distribution and timing of cell damage associated with olive fruit bruising and its use in analyzing susceptibility. Postharvest Biol. Technol. 111, 117–125. Jiménez, R., Rallo, P., Suárez, M.P., Morales-Sillero, A., Casanova, L., Rapoport, H.F., 2011. Cultivar susceptibility and anatomical evaluation of table olive fruit bruising. Acta Hortic. 924, 419–424. Jiménez-Jiménez, F., Castro-García, S., Blanco-Roldán, G.L., Ferguson, L., Uriel, A.R., GilRibes, J.A., 2013. Table olive cultivar susceptibility to impact bruising. Postharvest Biol. Technol. 86, 100–106. Lavee, S., Hanoch, E., Wodner, M., Abramowitch, H., 2007. The effect of predetermined deficit irrigation on the performance of cv. Muhasan olives (Olea europaea L.) in the eastern coastal plain of Israel. Sci. Hortic. 12 (2), 156–163. Marra, F.P., Marino, G., Marchese, A., Caruso, T., 2016. Effects of different irrigation regimes on a super-high-density olive grove cv. ‘Arbequina’: vegetative growth, productivity and polyphenol content of the oil. Irrig. Sci. 34 (4), 313–325. Morales-Sillero, A., Rallo, P., Jiménez, R., Casanova, L., Suárez, M.P., 2014. Suitability of
Fig. 6. Histological sections of mesocarp and epidermis in undamaged fruits of the cultivar Manzanilla de Sevilla at harvest: (A) Control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58) and -1.4 MPa until harvest (September 19th, 2017; DOY 262; DAFB 157), (B) RDI-3 treatment (-1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August (August 29th, 2017; DOY 241; DAFB 136) and then the fruit was rehydrated until harvest (regular recovery)). A lower thickness of cuticle may be observed in sections from the control treatment (A) with respect to RDI3 treatment (B). DOY: Day of year; DAFB: Days after full bloom.
treatment for the tree and the fruits, and the less water consuming treatment. RDI-3 produces fruits with average weight, volume and oil content similar to the control. The increase in the number of fruits per kg might be caused by the loss of fruit moisture in the RDI treatments as the Stress Integral increases but, even so, more than 90% of the fruits are classified within commercial categories. Furthermore, this severe water stress treatment with late rehydration (RDI-3) reduces the size of fruit bruises in comparison to early rehydration strategy. This is a very interesting result since bruising incidence is one the main factors limiting table olive commercial quality.
Acknowledgements This research was supported by Spanish Research Agency (AEI) of the Ministry of Economy, Industry and Competitiveness (MINECO) and European Development Fund (FEDER), projects AGL2013-45922-C2-1272
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Kalamata) in different irrigation regimes. Food Chem. 77, 27–34. Rallo, L., Díez, C.M., Morales-Sillero, A., Miho, H., Priego-Capote, F., Rallo, P., 2018. Quality of olives: a focus on agricultural preharvest factors. Sci. Hortic. 233, 491–509. Rapoport, H.F., Pérez-López, D., Hammami, S.B.M., Aguera, J., Moriana, A., 2013. Fruit pit hardening: physical measurements during olive growth. Ann. Appl. Biol. 163, 200–208. Sakai, W.S., 1973. Simple method for differential staining of paraffin embedded plant material using toluidine blue O. Stain Technol. 48 (5), 247–249. Sena‐Moreno, E., Pérez‐Rodríguez, J.M., De Miguel, C., Henar Prieto, M., Nieves Franco, M., Cabrera‐Bañegil, M., Martín-Vertedor, D., 2017. Pigment profile, color and antioxidant capacity of Arbequina virgin olive oils from different irrigation treatments. J. Am. Oil Chem. Soc. 94 (7), 935–945. Scholander, P.F., Hammel, H.T., Bradstreest, E.A., Hemmingsen, E.A., 1965. Sappressure in vascular plant. Science 148, 339–346.
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Bruising response in ‘Manzanilla de Sevilla’ olives to RDI strategies based on water potential
T
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L. Casanovaa, , M. Corella,b, M.P. Suáreza, P. Ralloa, M.J. Martín-Palomoa,b, A. Morales-Silleroa, A. Morianaa,b, M.R. Jiméneza a Departamento de Ciencias Agroforestales. Escuela Técnica Superior de Ingeniería Agronómica, ETSIA, Universidad de Sevilla, Ctra. de Utrera s/n, Km 1, Sevilla, 41013, Spain b Unidad Asociada al CSIC de Uso sostenible del suelo y el agua en la agricultura (US-IRNAS), Ctra. de Utrera Km 1, 41013, Sevilla, Spain
A R T I C LE I N FO
A B S T R A C T
Keywords: Table olive Fruit damage Cuticle Pit hardening Stem water potential (SWP) Stress integral
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.
1. Introduction The olive tree (Olea europaea L.) has been traditionally rainfed, but intensification and productivity increase have favored its transformation to an irrigate crop in the last decades. At present, water scarcity in arid and semi-arid regions such as Spain has expanded the irrigation programming technique called Regulated Deficit Irrigation (RDI). This irrigation programming is based on the existence of plant phenological stages that are more water stress resistant during which the water applied may be reduced without significantly affecting the yield or the fruit quality (Behboudian and Mills, 1997). RDI was developed at the beginning of the 80’s in peach (Chalmers et al., 1981) whereas the use of RDI in olive orchards was firstly described by Goldhamer (1999) at the end of the 90’s. Nowadays, RDI strategies have been implanted in oil olive plantations (Lavee et al., 2007; Iniesta et al., 2009; Fernández et al., 2013; Gómez del Campo et al., 2014; Carrillo et al., 2018) and recently in table olive orchards (Correa-Tedesco et al., 2010; Corell
⁎
et al., 2018). In olive, pit hardening has been commonly reported as the most resistant phenological stage (Goldhamer, 1999; Moriana et al., 2003; Iniesta et al., 2009). Moriana et al. (2012) proposed the use of stem water potential (SWP) thresholds measured at mid-day to maintain an adequate water status: -1.2 MPa for the flowering-fruit set phase and -1.4 MPa for the massive pit hardening phase in ‘Manzanilla de Sevilla’. However, the level of water stress at pit hardening may be higher without affecting the harvest, with an adequate rehydration (Moriana et al., 2003; Iniesta et al., 2009). A water stress of -2.0 MPa would not affect the fruit development (Dell’Amico et al., 2012), although a reduction of fruit size could occur if the deficit period is too long (Girón et al., 2015). Values below -3.5 MPa reduced current season productivity in cv Arbequina (Marra et al., 2016). Rehydration during the last part of the fruit growth period, once pit hardening is finished, resumes the growth of the olive fruit so that no differences are found at harvest (Girón et al., 2015).
Corresponding author. E-mail address: [email protected] (L. Casanova).
https://doi.org/10.1016/j.agwat.2019.06.007 Received 2 February 2019; Received in revised form 30 April 2019; Accepted 6 June 2019 Available online 14 June 2019 0378-3774/ © 2019 Elsevier B.V. All rights reserved.
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(RDI) strategies based on water status measurements, with stem water potential measure. The irrigation treatments were a control and three RDI (Table 1). Control treatment consisted in optimal plant water status (-1.2 MPa before the beginning of pit hardening and recovery (-1.4 MPa) until harvest. RDI-1 was -1.2 MPa before the beginning of pit hardening and a moderate water stress (-2 MPa) from the beginning of pit hardening until late August (August 29th, 2017; DOY 241; DAFB 136) and then the fruit was rehydrated (-1.4 MPa) until harvest (regular recovery); RDI-2 was -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late July (July 26th, 2017; DOY 206; DAFB 101) and then the fruit was rehydrated (-1.4 MPa) until harvest (early recovery); and RDI-3 was -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated (-1.4 MPa) until harvest (regular recovery). The beginning of the pit hardening period was considered as the moment when the rate of longitudinal fruit growth decreased (Rapoport et al., 2013). The experimental layout was a randomized design with four blocks and 12 trees per plot, arranged in three lines. The two central trees were measured and all adjacent trees were guard trees. Fruits were hand harvested at three different sampling dates: beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58), beginning of regular recovery (August 29th, 2017; DOY 241; DAFB 136), and the last date coinciding with harvest (September 19th, 2017; DOY 262; DAFB 157) in the ripening stage for green processing (Maturity Index = 1, Ferreira (1979)). For each treatment, replicate and sampling date the effect of RDI was quantified by several parameters: fruit weight (g), fruit volume (mL), fruit moisture (%), pulp-to-pit ratio (on fresh and dry weight basis), firmness (kg) and oil content (% on dry weight). Fruit weight (g) and the pulp-to-pit ratio (on fresh basis) were determined in subsamples of 0.5 kg of fruits. The pulp-to-pit ratio was determined in fresh weight as the difference between fruit and pit weights. Fruits were dried at 105 °C for 48 h to stable weight, and moisture content (%) and the pulpto-pit ratio on dry weight basis were determined. Oil content was also estimated by a NMR analyser Minispec NMS100 (Bruker Optik GmbH, Ettlingen, Germany) according to Del Río and Romero (1999) using 100 fruits. Fruit volume (mL) was measured from the volume of water displaced on immersion of 100 fruits in a graduated beaker with water. Firmness (kg) of table olives was measured in a subsample of 30 fruits using a fruit pressure tester called Penetrometer (Model FT 327 (3–27 Lbs.)), with a strut of 2 mm of diameter attached at the tip. The strut was slowly introduced in each fruit assessing its firmness. At harvest, fruit size distribution (fruits kg−1) was also calculated. Midday stem water potential (SWP) was measured weekly in one leaf per tree with the pressure chamber (Model 1000, PMS, USA) using the Scholander et al. (1965) technique from March 30th, 2017 (DOY 89) until September 19th, 2017 (DOY 262; DAFB 157) and it was used to characterize the water status of trees for each treatment. The leaves near the main trunk were covered in aluminum foil at least two hours before measurements were taken. In order to describe the accumulative effect of the water deficit, the water Stress Integral (SI) was calculated from the Ψ data (Myers, 1988) during the period of water stress (Eq. (1)). Eq. (1) used a reference of -1.4 MPa. The expression used was:
The effect of RDI strategies on olive oil quality has been long studied by different authors (Patumi et al., 2002; Sena‐Moreno et al., 2017; Ahumada et al., 2018), whereas there is very little information concerning the effect of RDI strategies on table olive fruit quality which has not been considered until recently (Cano-Lamadrid et al., 2015; Casanova et al., 2017). Fruit appearance is key for table olives since any defect on the surface of the fruit may cause consumer rejection and may reduce its market value. Thus, the absence of bruises is a relevant table olive quality trait (Rallo et al., 2018). Bruising is the most common mechanical damage of the olive fruit, usually occurring during harvesting and characterized by the formation of more or less extensive superficial browning injuries (Gambella et al., 2013; Jiménez et al., 2017) and cell damage (cell rupture and loss of cell wall thickness) extended into the mesocarp. Bruising is influenced by preharvest and postharvest factors such as the cultivar (Jiménez-Jiménez et al., 2013; Jiménez et al., 2016), the irrigation regime (Cano-Lamadrid et al., 2015; Casanova et al., 2017) or the mechanization of harvesting (Morales-Sillero et al., 2014). Nowadays, bruise susceptibility is the main limitation to table olive mechanical harvesting (Morales-Sillero et al., 2014). ‘Manzanilla de Sevilla’ is one of the most important table olive cultivars worldwide but it is more susceptible to bruising than other table olive varieties like ‘Hojiblanca’ (Jiménez-Jiménez et al., 2013; Jiménez et al., 2016) or ‘Manzanilla Cacereña’ (Morales-Sillero et al., 2014; Jiménez et al., 2017). Differences in bruise susceptibility seems to be a function of several physico-mechanical properties such as size, pulp to pit ratio, water status, fruit firmness and fruit structural traits as cuticle thickness (Hammami and Rapoport, 2012; Jiménez-Jiménez et al., 2013; Jiménez et al., 2017). Concerning water status, Casanova et al. (2017) studied the effect of water stress in the sensitive crop phase (-1.2 MPa before pit hardening and withholding until -2.5 MPa four weeks before harvest without recovery) on bruising. They found that a moderate water deficit entails a reduction of 50% of irrigation water without affecting fruit weight, volume or pulp-to-pit ratio (on fresh and dry weight basis) in Manzanilla de Sevilla cv. and improves fruit resistance to bruising, as evidenced by the lower bruising index and the lower external and internal damaged area. 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 has been studied in the same cultivar. Several fruit quality traits have also been determined, namely weight (g), size (fruit kg−1), moisture content (%), pulp-to-pit ratio (on fresh and dry weight basis), and oil content (% dry weight), as well as important anatomical features related to the cuticle and the epidermis. 2. Material and methods 2.1. Plant material and location of trial Fruits of thirty years old ‘Manzanilla de Sevilla’ table olive trees were evaluated in this study throughout the fruit growing season of the 2017 year. Trees were cultivated in a commercial orchard in Dos Hermanas (Seville, Southern Spain, 37°15′00″N, 5°56′54″O and 42 m altitude, ETRS 89) in a standard layout of 7 m by 4 m (357 trees ha−1), under an irrigation system in a well-established olive grove in full production. The full flowering was on April 15th, 2017 (Day of year (DOY) 105), the beginning of pit hardening was on June 12th, 2017 (DOY 163, Days after full bloom (DAFB) 58) and the harvest was on September 19th, 2017 (DOY 262, DAFB 157). Climatic conditions occurred along the experimental year are presented in Fig. 1.
SI = |∑(Ψ-(-1.4))|∗n
(1)
Where: SI is the stress integral, Ψ is the average midday stem water potential for any interval, and n is the number of the days in the interval. Linear regression between Stress Integral and fruit moisture was determined.
2.2. Experiment design and measurements Table olive trees were evaluated under regulated deficit irrigation 266
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Fig. 1. a. Seasonal daily reference Evapotraspiration (circles) and Rain (bars). b. Seasonal daily maximum air temperature (circles) and maximum vapor pressure deficit (VPD) (triangles). Table 1 Irrigation treatments: Control and Regulated Deficit Irrigation (RDI) strategies based on water status measurements. Midday stem water potential (SWP) thresholds Beginning of pit hardening June 12th, 2017 (DOY 163, DAFB 58) Treatment
Before
After
Recovery
Control RDI-1 RDI-2 RDI-3
−1.2 MPa −1.2 MPa −1.2 MPa −1.2 MPa
−1.4 MPa −2.0 MPa −3.5 MPa −3.5 MPa
Regular recovery: August 29th, 2017 (DOY 241; DAFB 136) Early recovery: July 26th, 2017 (DOY 206; DAFB 101) Regular recovery: August 29th, 2017 (DOY 241; DAFB 136)
DOY: Day of year; DAFB: Days after full bloom.
fruits was bruise-induced by letting them fall from one meter high according to methodology proposed by Jiménez et al., 2016. The percentage of bruised fruits (%) and the bruise index were also quantified three hours after the impact, and then fixed in a FAE solution (formalin, acetic acid, 95% ethanol and distilled water (10:5:50:35 v/v/v/v) (Berlyn and Miksche, 1976). External bruise area and volume were quantified according to the methodology by Morales-Sillero et al. (2014) in 30 damaged fruits (bruise-induced) per treatment and
2.3. Bruising measurements At harvest time, a sample of about 2.5 kg of fruits was taken for each treatment and replicate. Later, a subsample of one hundred fruits per treatment and replicate was selected and the percentage of bruised fruits (%) and the bruise index (0 (no bruising) to 2 (severe bruising)) were quantified at 3 h after harvest according to Morales-Sillero et al. (2014). Furthermore, another subsample of one hundred undamaged 267
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replicate. Previously, to eliminate FAE solution, about three weeks after, the subsamples were introduced in ethanol 70% solution. Ten damaged fruits per treatment and replicate were rehydrated according to Gucci et al. (2009), to quantify Internal Damage Area (mm2). Damaged mesocarp portions were obtained and evaluated according to the methodology described by Jiménez et al. (2016). Internal Damage Area (mm2) was quantified in photographic images taken with a Nikon Digital camera (Sight DS Ri 1) connected to a binocular loupe Nikon (Nikon, SMZ 1270, Tokyo, Japan) and analyzed with Nis-Elements AR 3.2 image analysis software. 2.4. Characterization of the cuticle and epidermis features For each treatment, replicate and sampling date, the cuticle and epidermal cell features were also quantified in mesocarp portions after a histological process described by Jiménez et al. (2016). First, ten undamaged fruit mesocarp portions were subjected to a process of dehydration (Berlyn and Miksche, 1976) and then were embedded in Histosec® embedding paraffin at a melting point of 56–58 °C (Merck, Darmstadt, Germany). Secondly, transverse sections of 12 μm thick were obtained with a rotary microtome (Reichert Histostat 820, Buffalo, USA). These histological sections were mounted on glass slides and stained with 0.05% toluidine blue for 60 min prior to paraffin removal (Sakai, 1973). Later, photographic images of all sections were taken with a Nikon Digital camera (Sight DS Ri 1) connected to a binocular loupe Nikon (Nikon, SMZ 1270, Tokyo, Japan) and with processed NisElements AR 3.2 image analysis software. Ten histological sections per treatment, replicate and date from undamaged fruits were used to assess the cuticle and epidermis features. In each histological section, three different random zones composed of ten consecutive cells were used. According to the methodology proposed by Hammami and Rapoport (2012), the combined epidermal area (Ar Ep, μm2) and length (L Ep, μm) of each cell group and the combined cuticle area (Ar Cu, μm2) were quantified. Then, the cuticle thickness (μm), cuticle area/cell (μm2), and both the epidermal cell radial (μm) and epidermal cell tangential widths (μm) were calculated as follows:
Cuticle thickness (μm) =
Cuticle area/cell(μm2) =
Fig. 2. Pattern of midday stem water potential along the experiment during 2017 season. Each point is the average of 4 data. Vertical bars represented standard error. First vertical line shows the beginning of pit hardening period, second show early recovery and third regular recovery. Stars indicates dates where statistical differences were significant (*P < 0.05; +P < 0.01, Tukey Test). Control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58) and -1.4 MPa until harvest (September 19th, 2017; DOY 262; DAFB 157). RDI-1: -1.2 MPa before the beginning of pit hardening and a moderate water stress (-2.0 MPa) from the beginning of pit hardening until late August (August 29th, 2017; DOY 241; DAFB 136) and then the fruit was rehydrated until harvest (regular recovery); RDI-2: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late July (July 26th, 2017; DOY 206; DAFB 101) and then the fruit was rehydrated until harvest (early recovery); RDI-3: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery). DOY: Day of year; DAFB: Days after full bloom.
treatment reached SWP of -1.48 MPa before pit hardening and -2.16 MPa afterwards, slightly lower than the theoretical defined water potential. RDI-1 treatment consisted in a moderate water stress during pit hardening; before pit hardening water potentials were similar to control (-1.63 MPa) and at the end of water stress period and before the beginning of regular recovery (DOY 241), minimum values of SWP were lower than the control (-3.08 MPa) due to a problem in the irrigation system, but they were completely recovered (around -1.40 MPa) at the end of the experiment (DOY 262). RDI-2 treatment consisted in a shorter period of water stress at pit hardening; before the beginning of pit hardening minimum SWP was near to control and the early recovery at late July (DOY 206) recuperated plant water status (-2.44 MPa) until the theorical level considered and no differences were found with control treatment (-2.16 MPa). RDI-3 treatment consisted in a severe water stress at pit hardening; as in the rest of treatments, no water stress was obtained before pit hardening (-1.58 MPa) and minimum SWP during the period of stress and recovery were reached before the beginning of the regular recovery (DOY 241), showing severe water stress conditions (-3.69 MPa) at DOY 220. In summary, SWP was similar in the four treatments before pit hardening (above -1.5 MPa). Later, SWP in all treatments decreased reaching values slightly below -2 MPa until late July (DOY 206), when water status of the different irrigation treatments began to differentiate. Statistically significant differences for SWP among irrigation treatments were observed at the beginning of the regular recovery period (DOY 241), especially between RDI-3 and the other treatments, though at harvest all trees showed similar values to the control (around -1.40 MPa) (Fig. 2). Taking into account the water relations (Table 2) and fruit quality
Ar Cu L Ep
Ar Cu 10
Epidermal cell radial width (μm) =
Ar Ep L Ep
Epidermal cell tangential width (μm)=
L Ep 10
2.5. Statistical analysis Data were analyzed with StatGraphics Plus V. 5.1 (Manugistics Inc., USA) by ANOVA to determine the effect of water stress treatments on fruit traits. The Tukey’s test (P < 0.05) was used to discriminate among the mean values. When necessary, data were previously transformed using Box-Cox power transformations (Box and Cox, 1964) to achieve normality and homogenize the variance. A linear regression between Stress Integral (SI, MPa day) and fruit moisture was also calculated. 3. Results and discussion RDI treatments in this work were theoretically defined to reach certain levels of water stress as explained in material and methods section, but the real pattern of midday stem water potential (SWP) reached during the irrigation season is shown in Fig. 2. Control 268
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among treatments, neither for minimum SWP (Fig. 2). Fruit quality traits as weight, volume, moisture, pulp-to-pit ratio (on fresh and dry basis), and oil content (% dry weight) showed no differences between RDI treatments and control at this phenological stage (Table 3). Statistical differences were found in firmness among treatments, but later they disappeared. Until late August (after early recovery and at the beginning of regular recovery) (DOY 89-241), there were significant differences in the minimum SWP and Stress Integral especially between RDI-3 and the other treatments (Fig. 2 and Table 2); RDI-1 induced a moderate water stress and since early recovery of RDI-2 treatment had already taken place (DOY 206), none of those treatments differed significantly from the control (-2.16 MPa). In fact, RDI-2 (early recovery of punctual water stress) was the less stressed RDI treatment (48.29 MPa day), without significant differences with respect to control and the regular recovery of moderate water stress treatment RDI-1 (64.08 MPa day) and severe water stress treatment RDI-3 (89.06 MPa day) was significantly the most stressed treatment. For RDI-3 the regular recovery was slower, thus the minimum SWP in this phase reached the lowest value (-3.69 MPa) (Fig. 2) and fruit weight, volume, moisture and pulp-to-pit ratio (on fresh and dry basis) decreased in this treatment with respect to the others treatments, but only significantly with respect to RDI-2 (Table 3). In addition, this treatment wasted less amount of water, and was the only treatment that significantly reduced total water applied with respect to the control treatment at harvesting (105 vs 274 mm, respectively) (Table 2). No differences among treatments were found in flesh firmness nor oil content at this period (Table 3). At harvest (DOY 262), none of the RDI treatments had effect on fruit weight (ranged between 4.01 and 4.60 g), volume (ranged between 4.00 and 4.71 mL), pulp-to-pit ratio on dry basis (ranged between 2.25 and 2.50), firmness (ranged between 1.09 and 1.17 kg) or oil content (38.90 and 41.66%) (Table 3) because regular (late August) or early (late July) recovery reduced water stress of the fruits before harvest, as Girón et al. (2015) observed. However, the pulp-to-pit ratio on fresh weight basis was significantly different between RDI-2 and RDI-3 (7.70 and 6.37, respectively) (Table 3). Furthermore, although RDI treatments didn’t significantly modify mean fruit weight, the number of fruit kg−1 was increased in RDI-3 (Fig. 3). Such effect was likely related with irrigation scheduling because the yield of the trees were very similar (Table 2). This was probably related to fruit moisture which linearly decreased with increasing Stress Integral (R2 = 0.6381) (Fig. 4), and the RDI-3 fruits showed the lowest values (62.98%) with respect to the
Table 2 Yield (kg tree−1) at harvest and cumulative values of Applied water (mm) and Stress Integral (MPa day) from March 30th, 2017 (DOY 89) until the beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58), until the beginning of early recovery (July 26th, 2017; DOY 206; DAFB 101), until the beginning of regular recovery (August 29th, 2017; DOY 241; DAFB 136) and until harvest (September 19th, 2017; DOY 262; DAFB 157). Weekly measurements. Cumulated period until
Treatment
Beginning of pit hardening
Control RDI-1 RDI-2 RDI-3 Control RDI-1 RDI-2 RDI-3 Control RDI-1 RDI-2 RDI-3 Control RDI-1 RDI-2 RDI-3
Beginning of early recovery Beginning of regular recovery Harvest
Yield (kg tree−1)
Applied water (mm)
Stress Integral (MPa day)
34.2 26.6 38.7 29.5
19 ± 7 33 ± 22 19 ± 11 23 ± 14 31 ± 5 45 ± 29 19 ± 11 23 ± 14 247 ± 40 b 172 ± 26 ab 301 ± 95 b 32 ± 15 a 274 ± 35 b 295 ± 39 b 360 ± 52 b 105 ± 14 a
1.98 ± 1.61 3.31 ± 2.53 2.78 ± 1.56 4.22 ± 1.68 17.15 ± 5.44 a 29.04 ± 9.79 ab 30.75 ± 8.68 ab 32.76 ± 8.07 b 31.34 ± 11.20 a 64.08 ± 17.38 b 48.29 ± 13.12 ab 89.06 ± 28.17 b 33.70 ± 6.69 a 70.69 ± 9.74 ab 51.27 ± 6.93 a 97.9 ± 15.39 b
± ± ± ±
5.6 3.1 1.4 3.9
Different letters indicate significant differences among treatments according to the Tukey Test (P < 0.05) for each parameter and date. Control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening and -1.4 MPa until harvest. RDI-1: -1.2 MPa before the beginning of pit hardening and a moderate water stress (-2.0 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery); RDI-2: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late July and then the fruit was rehydrated until harvest (early recovery); RDI-3: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery). DOY: Day of year; DAFB: Days after full bloom.
(Table 3) we can describe the effect of water stress in different phenological stages. At the beginning of the studied period (DOY 89-163), before the beginning of pit hardening, the Stress Integral ranged from 1.98 (Control) to 4.22 MPa day (RDI-3) without significant differences
Table 3 Effect of RDI treatments on fruit traits in three moments: beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58), beginning of regular recovery (August 29th, 2017; DOY 241; DAFB 136) and at harvest (September 19th, 2017; DOY 262; DAFB 157). Date
Treatment
Fruit Weight (g)
Fruit Volume (ml)
Fruit Moisture (%)
Pulp-to-pit ratio (on fresh weight basis)
Pulp-to-pit ratio (on dry weight basis)
Firmness (kg)
Beginning of pit hardening
Control RDI-1 RDI-2 RDI-3 Control RDI-1 RDI-2 RDI-3 Control RDI-1 RDI-2 RDI-3
1.78 1.85 1.81 1.81 3.67 3.47 3.86 3.16 4.42 4.40 4.60 4.01
1.63 1.54 1.50 1.63 3.62 3.50 3.87 3.00 4.33 4.25 4.71 4.00
63.31 62.83 62.30 62.45 66.28 63.62 65.51 59.23 67.09 65.75 66.96 62.98
1.88 2.00 1.87 1.87 4.85 4.85 5.67 3.86 6.99 6.92 7.70 6.37
0.86 0.86 0.83 0.82 1.77 1.93 1.92 1.73 2.30 2.50 2.45 2.25
1.86 1.77 1.66 1.77 1.61 1.65 1.55 1.67 1.17 1.12 1.09 1.14
Beginning of regular recovery
Harvest
± ± ± ± ± ± ± ± ± ± ± ±
0.10 0.20 0.06 0.09 0.39 0.26 0.39 0.19 0.52 0.50 0.34 0.11
ab ab b a
± ± ± ± ± ± ± ± ± ± ± ±
0.08 0.16 0.14 0.08 0.48 0.45 0.31 0.24 0.54 0.57 0.39 0.49
ab ab b a
± ± ± ± ± ± ± ± ± ± ± ±
0.66 1.07 0.39 0.16 0.71 1.01 0.84 5.51 0.66 0.26 0.73 0.71
b ab b a c b bc a
± ± ± ± ± ± ± ± ± ± ± ±
0.10 0.08 0.11 0.11 0.33 0.36 1.20 0.46 0.50 0.81 0.47 0.34
ab ab b a ab ab b a
± ± ± ± ± ± ± ± ± ± ± ±
0.11 0.04 0.04 0.11 0.13 0.11 0.02 0.02 0.12 0.12 0.14 0.11
ab b b a
± ± ± ± ± ± ± ± ± ± ± ±
0.09 0.06 0.03 0.06 0.14 0.13 0.09 0.06 0.13 0.10 0.10 0.04
Oil content (% dry weight)
b ab a ab
0.69 ± 0.65 0.72 ± 0.40 0.48 ± 0.34 0.94 ± 0.68 31.71 ± 1.20 32.13 ± 2.44 34.63 ± 3.52 34.20 ± 1.01 39.38 ± 0.98 40.69 ± 1.92 38.90 ± 2.80 41.66 ± 0.95
Different letters indicate significant differences among treatments according to the Tukey Test (P < 0.05) for each parameter and date. Control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening and -1.4 MPa until harvest. RDI-1: -1.2 MPa before the beginning of pit hardening and a moderate water stress (-2.0 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery); RDI-2: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late July (July 26th, 2017; DOY 206; DAFB 101) and then the fruit was rehydrated until harvest (early recovery); RDI-3: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery). DOY: Day of year; DAFB: Days after full bloom. 269
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Fig. 3. Fruit size distribution at harvest in RDI and control treatments. Control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58) and -1.4 MPa until harvest (September 19th, 2017; DOY 262; DAFB 157). RDI-1: -1.2 MPa before the beginning of pit hardening and a moderate water stress (-2.0 MPa) from the beginning of pit hardening until late August (August 29th, 2017; DOY 241; DAFB 136) and then the fruit was rehydrated until harvest (regular recovery); RDI-2: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late July (July 26th, 2017; DOY 206; DAFB 101) and then the fruit was rehydrated until harvest (early recovery); RDI-3: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery). DOY: Day of year; DAFB: Days after full bloom.
RDI treatments neither affected bruised fruits (ranging between 24.28% for RDI-3 and 28.28 for RDI-2) nor bruise index (ranged between 0.24 for RDI-3 and 0.28 for RDI-2), when fruits were hand harvested (Table 4). After an induced impact, the percentage of bruised fruits and bruise index increased to 94% and 1.0 approximately, without differences among RDI treatments and control. When fruits were hand harvested all bruised fruits were classified as low-damaged, but when fruits were bruise induced, the percentage of severe-damage ranged between 4.51 for RDI-1 and 9.29 for RDI-2 without significant differences among RDI treatments in any case. Similar bruising values were observed by Jiménez et al. (2011) for ‘Manzanilla de Sevilla’ fruits after an induced impact. Nevertheless, external damaged area and bruise volume decreased significantly in the most water stressed fruits (RDI-3) (36.02 mm2 and 66.83 mm3, respectively), compared to the early recovery treatment (RDI-2) (43.27 mm2 and 96.85 mm3, respectively) that finally received the same applied water as the control (Table 2). These results are in agreement with Casanova et al. (2017) who studied the effect of RDI in the sensitive crop phase (-1.2 MPa before pit hardening and withholding until -2.5 MPa four weeks before harvest without recovery). With respect to the internal damage, an evident discoloration through the mesocarp was observed in the bruised mesocarp sections. The discoloration was surrounded by a darker halo
Fig. 4. Linear regression between Stress Integral (SI, MPa day) and fruit moisture (%) at harvest.
control fruits (67.09%) (Table 3). Despite this, 93.75% of the fruits from RDI-3 were classified within commercial categories (< 340-360 fruits kg-1) according to the Spanish trade standard regulation for table olives cv. Manzanilla de Sevilla (Orden CAPDR, 49066/, 2018). These results suggested that the recovery period could compensate severe water stress level as in RDI-1. Such level of water stress is similar to the ones suggested by Girón et al. (2015). Table 4 Effect of RDI treatments on fruit bruising at harvest. Treatment
Manual Harvesting
Induced Impact
Total bruised fruits (%) No bruised fruits (%) Fruits with low damage (%) Fruits with severe damage (%) Bruise Index Total bruised fruits (%) No bruised fruits (%) Fruits with low damage (%) Fruits with severe damage (%) Bruise Index Internal Damaged Area (mm2) External Damaged Area (mm2) Bruise Volume (mm3)
Control
RDI-1
RDI-2
RDI-3
26.45 ± 4.44 73.55 ± 4.44 26.45 ± 4.44 0.00 ± 0.00 0.26 ± 0.04 94.66 ± 2.30 5.34 ± 2.30 89.81 ± 3.08 4.85 ± 3.14 0.99 ± 0.05 15.51 ± 1.22 40.49 ± 3.78 ab 91.50 ± 18.37 ab
26.25 ± 6.13 73.75 ± 6.13 26.25 ± 6.13 0.00 ± 0.00 0.26 ± 0.06 93.99 ± 3.91 6.01 ± 3.91 89.47 ± 2.07 4.51 ± 1.93 0.98 ± 0.06 14.37 ± 1.75 43.46 ± 0.75 b 95.47 ± 10.89 ab
28.28 ± 4.85 71.71 ± 4.85 28.04 ± 4.43 0.25 ± 0.49 0.28 ± 0.06 94.17 ± 3.08 5.82 ± 3.08 84.88 ± 2.38 9.29 ± 3.55 1.03 ± 0.06 15.53 ± 2.68 43.27 ± 2.70 b 96.85 ± 10.87 b
24.28 ± 5.76 75.72 ± 5.76 24.02 ± 6.18 0.25 ± 0.51 0.24 ± 0.06 94.00 ± 4.22 5.99 ± 4.22 85.02 ± 6.83 8.98 ± 4.60 1.03 ± 0.06 15.64 ± 3.43 36.02 ± 3.12 a 66.83 ± 8.93 a
Different letters indicate significant differences among treatments according to the Tukey Test (P < 0.05) for each parameter. Control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58) and -1.4 MPa until harvest (September 19th, 2017; DOY 262; DAFB 157). RDI-1: -1.2 MPa before the beginning of pit hardening and a moderate water stress (-2.0 MPa) from the beginning of pit hardening until late August (August 29th, 2017; DOY 241; DAFB 136) and then the fruit was rehydrated until harvest (regular recovery); RDI-2: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late July (July 26th, 2017; DOY 206; DAFB 101) and then the fruit was rehydrated until harvest (early recovery); RDI-3: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery). DOY: Day of year; DAFB: Days after full bloom. 270
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Fig. 5. Mesocarp portions of ‘Manzanilla de Sevilla’ 3 h after bruise induction impact, and prior to the histological procedure: (A) Fixed tissue portions from control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58) and -1.4 MPa until harvest (September 19th, 2017; DOY 262; DAFB 157). (B) Fixed tissue portions from RDI-3 treatment (-1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August (August 29th, 2017; DOY 241; DAFB 136) and then the fruit was rehydrated until harvest (regular recovery)). DOY: Day of year; DAFB: Days after full bloom. Table 5 Effect of RDI treatments on cuticle and epidermal cell features in three moments: beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58), beginning of regular recovery (August 29th, 2017; DOY 241; DAFB 136) and at harvest (September 19th, 2017; DOY 262; DAFB 157). Cuticle
Beginning of pit hardening
Beginning of regular recovery
Harvest
Epidermal cell size
Treatment
Thickness (μm)
Area/cell (μm2)
Radial width (μm)
Tangential width (μm)
Area (μm2)
Control RDI-1 RDI-2 RDI-3 Control RDI-1 RDI-2 RDI-3 Control RDI-1 RDI-2 RDI-3
8.93 ± 2.75 8.38 ± 2.64 7.73 ± 1.54 8.64 ± 1.44 10.93 ± 1.05 12.11 ± 1.75 11.50 ± 1.46 11.87 ± 1.31 11.07 ± 1.59 11.30 ± 1.41 11.05 ± 1.26 12.05 ± 1.70
179.81 168.74 152.59 181.27 265.79 292.95 283.20 293.29 262.36 272.40 282.70 291.26
16.38 16.30 16.59 16.59 14.51 13.95 13.90 14.19 14.47 14.23 14.35 14.25
20.24 20.13 19.69 20.91 24.24 24.24 24.68 24.74 23.73 24.16 24.67 24.18
332.47 326.91 326.72 347.25 350.59 337.65 342.06 350.20 343.18 343.93 353.19 344.62
± ± ± ± ± ± ± ± ± ± ± ±
52.73 55.38 34.03 35.37 39.58 49.03 34.49 43.83 39.27 33.45 42.48 45.02
± ± ± ± ± ± ± ± ± ± ± ±
1.49 1.32 1.50 1.30 1.34 0.99 1.63 1.54 1.47 0.92 1.28 1.01
± ± ± ± ± ± ± ± ± ± ± ±
1.81 1.67 0.99 1.32 1.99 2.35 1.37 2.04 1.70 1.35 2.66 1.92
± ± ± ± ± ± ± ± ± ± ± ±
47.51 26.22 37.17 37.33 32.91 37.67 38.12 42.50 36.32 30.03 37.69 33.85
Different letters indicate significant differences between treatments according to the Tukey Test (P < 0.05) for each parameter and date. Control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening and -1.4 MPa until harvest. RDI-1: -1.2 MPa before the beginning of pit hardening and a moderate water stress (-2.0 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery); RDI-2: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late July (July 26th, 2017; DOY 206; DAFB 101) and then the fruit was rehydrated until harvest (early recovery); RDI-3: -1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August and then the fruit was rehydrated until harvest (regular recovery). DOY: Day of year; DAFB: Days after full bloom.
presented the greater epidermal cell radial width (14.47 μm) and regular recovery treatments (RDI-1 and RDI-3) the lowest (14.23 and 14.25 μm, respectively) (Table 5). In spite of not having found significant differences for cuticle properties, the significant lower bruise damage observed in the most stressed treatment (RDI-3), both in the external area and volume of damaged fruit, could be related to the higher values observed for cuticle thickness and cuticle area per cell in the fruits of this treatment (Fig. 6 and Table 5). It is known that ‘Manzanilla de Sevilla’ is a bruise susceptible cultivar (Jiménez-Jiménez et al., 2013; Jiménez et al., 2016) and fruits present a thinner cuticle compared to other table varieties like Hojiblanca or Manzanilla Cacereña (Hammami and Rapoport, 2012; Jiménez et al., 2017) which are considered less susceptible to bruising. In our trial, the more stressed deficit irrigation treatment (RDI-3) seems to cause an increase in the cuticle thickness, as observed by other authors in some water stress conditions (Gómez del Campo et al., 2014; Patumi et al., 2002), although further research should be performed to confirm it.
and showed tissue ruptures inside without affecting the epidermis as previously described by Jiménez et al. (2016) (Fig. 5). No significant differences were neither found in the Internal Damaged Area values, that ranged between 14.37 mm2 (RDI-1) and 15.64 mm2 (RDI-3) (Table 4) although qualitatively, the discoloration in the most water stressed fruits (RDI-3) was lower (Fig. 5). RDI treatments had no significant effect on the cuticle and epidermis parameters during the fruit growing season from the beginning of pit hardening to harvest (Table 5). Regarding cuticle, at the beginning of pit hardening, the thickness ranged between 7.73 μm (RDI-2) and 8.93 μm (control) and cuticle area per cell ranged between 152.59 μm2 (RDI-2) and 181, 27 μm2 (RDI-3). At late August (regular recovery date) RDI fruits showed, however, thicker cuticle and larger cuticle area per cell (12.11 μm and 292.95 μm2 for RDI-1; 11.50 μm and 283.20 μm2 for RDI-2; 11.87 μm and 293.29 μm2 for RDI-3) than the control (10.93 μm and 265.79 μm2), although not significant. At harvest, the most stressed fruits (RDI-3) presented greater cuticle thickness (12.05 μm) and cuticle area per cell (291.26 μm2) and control fruits showed the lowest values for the same traits (11.07 μm and 262.36 μm2, respectively), even though the differences were again not significant (Table 5 and Fig. 6). Concerning epidermal cell size, no statistical differences were found at any date. At harvest, the RDI-2 fruits showed the largest tangential width (24.67 μm) and area (353.19 μm2) followed by RDI-3 fruits (24.18 μm and 344.62 μm2), and control fruits the lowest (23.73 μm and 343.18 μm2, respectively). Instead, control fruits
4. Conclusions The RDI-3 strategy (-1.2 MPa before the beginning of pit hardening and a severe water stress (-3.5 MPa) from the beginning of pit hardening until late August (DOY 241, DAFB 136) after which the fruit was rehydrated up to harvest (regular recovery)) was the most stressing 271
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R and AGL2016-75794-C4-4-R. The authors wish to thank the editor and the anonymous reviewers for detailed and constructive comments on earlier versions of this article. References Ahumada, L., Ortega-Farias, S., Searles, P.S., 2018. Olive oil quality response to irrigation cut-off strategies in a super-high density orchard. Agric. Water Manag. 202, 81–88. Behboudian, M.H., Mills, T.M., 1997. Deficit irrigation in deciduous orchards. Hortic. Rev. 21, 105–131. Berlyn, G.P., Miksche, J.P., 1976. Botanical Microtechnique and Cytochemistry, 3rd ed. Iowa State University Press, Ames, Iowa, USA. Box, G.E.P., Cox, D.R., 1964. An analysis of transformations. J. R. Stat. Soc. Ser. B 26 (2), 211–252. Cano-Lamadrid, M., Girón, I.F., Pleite, R., Burló, F., Corell, M., Moriana, A., CarbonellBarrachina, A.A., 2015. Quality attributes of table olives as affected by regulated deficit irrigation. Food Sci. Biotechnol. 62, 19–26. 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Suitability of
Fig. 6. Histological sections of mesocarp and epidermis in undamaged fruits of the cultivar Manzanilla de Sevilla at harvest: (A) Control treatment: optimal plant water status (-1.2 MPa before the beginning of pit hardening (June 12th, 2017; DOY 163; DAFB 58) and -1.4 MPa until harvest (September 19th, 2017; DOY 262; DAFB 157), (B) RDI-3 treatment (-1.2 MPa before the beginning of pit hardening and a water stress (-3.5 MPa) from the beginning of pit hardening until late August (August 29th, 2017; DOY 241; DAFB 136) and then the fruit was rehydrated until harvest (regular recovery)). A lower thickness of cuticle may be observed in sections from the control treatment (A) with respect to RDI3 treatment (B). DOY: Day of year; DAFB: Days after full bloom.
treatment for the tree and the fruits, and the less water consuming treatment. RDI-3 produces fruits with average weight, volume and oil content similar to the control. The increase in the number of fruits per kg might be caused by the loss of fruit moisture in the RDI treatments as the Stress Integral increases but, even so, more than 90% of the fruits are classified within commercial categories. Furthermore, this severe water stress treatment with late rehydration (RDI-3) reduces the size of fruit bruises in comparison to early rehydration strategy. This is a very interesting result since bruising incidence is one the main factors limiting table olive commercial quality.
Acknowledgements This research was supported by Spanish Research Agency (AEI) of the Ministry of Economy, Industry and Competitiveness (MINECO) and European Development Fund (FEDER), projects AGL2013-45922-C2-1272
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