*4.1.3. Effect on fruits and olive oils quality*

than vegetative growth. In the initial years of orchard establishment, when rapid vegetative growth is desirable in order to quickly obtain optimum tree size and canopy, as well as to begin fruit production as soon as possible, it is critical not to depress vegetative activity. For this reason, in commercial orchards, DI is commonly implemented only once, trees are fully grown to avoid negative effects on the formation of tree structure during the training period [102]. DI at early stages of tree development may result useful not only for water saving but also for controlling vigor in super high-density (SHD) orchards, in particular in regions where local conditions lead to excessive vegetative growth, such as in northern Argentina [103]. The choice and success of DI strategy is conditioned by tree density and rootzone size. It seems that SDI is more interesting when trees explore large volumes of soil, as in low-density orchards that maximize the availability of stored soil water per tree, compared to higher densities [97, 104]. Moreover, the success of SDI as compared to FI depends on the crop load of olive. About this issue, Martín-Vertedor et al.

of Spain. They observed that SDI (75% ETc) reduced yield in "on" years. Nevertheless, they reported that this DI could be advisable during "off" years, when a lower water use is observed, and trees are less sensitive to water deficit with low-crop load. There is still uncertainty about

Lavee et al. [107] suggested that the most efficient schedule for RDI irrigation was to withhold water till the end of endocarp hardening and then to apply full irrigation from that stage till

Often, DI strongly reduces vegetative growth, but only slightly reduces the final fruit volume. Water stress caused a higher reduction in fresh fruit yield than oil yield due to a higher oil concentration in DI irrigated trees "in Picual" (Spain), without differences between SDI and RDI [11]. Moreover, Iniesta et al. [11] observed that WP for oil production has tripled for a 25% decrease in total water applied. They conclude that both irrigation strategies may be used with moderate reductions (about 15%) in oil yield. Similarly, Fernandes-Silva et al. [12] ("Cobrançosa," Portugal) reported that for a SDI at 30% ETc, WP for oil is higher or very close to FI, depending on the year, and is more than double the one obtained in rainfed conditions; oil yield is reduced only 35% as compared to FI, while saving 60% of water applied. Nevertheless, oil concentration on a dry matter basis (DM) in SDI was 7–19% higher as compared to FI, hence oil yield reduction was lower than yield of fruit (DM). The higher oil yield observed in FI is mainly due to higher number of fruits, although under SDI, fruits have slight higher values of mesocarp (>3–5%) as compared to FI olives, mainly attributed to a higher crop load in FI olive trees. Fernandes-Silva et al. [12] founded a good relationship between the oil amount per mesocarp dry mass (g) (y = 0.83 × −0.17, r2 = 0.97). This may be useful in supporting the decision of the most suitable time for harvest to optimize oil productivity.

Irrigation is particularly an important component in SHD orchards as the trees are expected to have more reduced volume of the rootzone. There is not a consensus on the best irrigation approach for SHD olive orchards. A reduction in water applied up to 16% in July did not

), in the Southwest

) under FI [63],

[109].

[105, 106] conducted a long term studied in "Morisca" orchard (417 trees ha−<sup>1</sup>

The literature provides results, for low-density orchards (300–600 trees ha−<sup>1</sup>

SDI [12], RDI [11], and PRD [108] and for SHD olive orchards >1500 trees ha−<sup>1</sup>

which DI strategies are better, regarding SDI or RDI [58, 101].

2 weeks prior to harvest.

60 Irrigation in Agroecosystems

The concept of quality in fruit products is wide, complex, and dynamic. In the case of olive trees, two main products are obtained from olive fruits: virgin olive oil (the juice of the fruit) and table olives; both are staple foods of the Mediterranean diet. The quality attributes that are considered for each product largely differ from one another.

High irrigation rates are associated with a decrease mainly in minor compounds of virgin olive oil (VOO) as they are total polyphenols (TP), orto-diphenols (OD), tocopherols (TC) volatile compounds (VC) [16, 114] that have an important role in nutritional value, biological proprieties, and organoleptic characteristics of VOO. There is a controversy about the effect of irrigation in overall quality of VOO. In the literature, there are researchers who argue that FI lowers the quality of olive oil [115]. If this may be true for Cvs poor in TP, such as "Arbequina," FI may compromise the conditions necessary for virgin extra category and in other hand, decrease its self-live time. Nonetheless, in Cvs very rich in PT (>1000 mg/kg), such as "Cornicabra," VOO is very bitter and pungent, and therefore with poor acceptability by the consumer, FI may help to overcome this problem.

olives ("Manzanilla"), after processing that were previously submitted to three irrigation

with low stress at the end of flowering stage, and moderate during pit hardening. They observed that FI olives had the highest weight and size, and were rounded. Color coordinates

predominated in FI olive fruits, while terpenes and polyunsaturated fatty acids predominated

consumers due to fresh olive flavor, crunchiness, and global satisfaction. They argue that both RDIs are effective and can be a good alternative irrigation practice for this cultivar. However, these authors evaluated table olives quality after processing, an evaluation after harvest, that

Water deficit effect could increase of PhytoPs content, chemical compounds analogs to prostaglandin, which belong to a novel family of plant effectors, may be related to the enhancement of reactive oxygen species (ROS) production under drought stress, which induce the formation of an array of lipid peroxidation products [123]. The phase II of fruit growth can be noncritical considering fruit yield or fruit size [124] but is clearly critical for PhytoPs formation. Thus, olive table trees under RDI can be considered as complementary actions to enhance the PhytoP content and hence their potential beneficial effects on human health as they play a role

RDI is based on restraining irrigation during certain periods of the vegetative cycle of the crop, therefore implying the knowledge of the several phases and sometimes its differences between genotypes, since the length of some phases (fruit development period and ripening) varies for early-maturing or late varieties [126]. The phenological stages of peach *Prunus persica* L. Batsch) can be depicted as shown in **Figure 1**. During the fruit growth period, three phases are classically considered: phases I and III, where rapid growth occurs and a phase II characterized by a plateau [127] having the growth curve, a double sigmoid pattern [128].

Several studies over the last decades have addressed the use of deficit irrigation, namely RDI, in peach. Ref. [31] have applied the method to peach during the phase of final swell and observed a significant production and fruit growth increase, if irrigation restrictions were applied while excessive vegetative vigor could be suppressed to favor fruit growth. Mitchell and Chalmers [32] have used RDI during the phase of fast vegetative growth, obtaining similar yield and fruit growth to a nonrestricted situation, while saving ca. 30% of irrigation water and controlling the vegetative growth. For the post-harvest phase, [129] observed that irrigation reduction decreased pruning requirements and increased flowering in the next season. For the same phase, and also during fruit development, [130] saved 40% of irrigation water with light implications in production and fruit size. More recently, the benefits of applying

with moderate stress during pit hardening (soft water stress) and RDI2

Deficit Irrigation in Mediterranean Fruit Trees and Grapevines: Water Stress Indicators and Crop…

olives. Aldehydes and monounsaturated fatty acids

olives, with high satisfaction degree among

olives. Sensory evaluation indi-

http://dx.doi.org/10.5772/intechopen.80365

63

treatments: FI; RDI1

L\* and b\* had the highest values in RDI2

in regulation of immune function [125].

*4.2.1. Vegetative and productive cycle*

*4.2.2. Peach response to water stress*

**4.2. Peach**

cated that global acceptance was higher for RDI1

is, before olives processing may be more interesting.

in T1 fruits, and saturated fatty acids were abundant in RDI<sup>2</sup>

Motilva et al. [116] observed that RDI strategies applied to "Arbequina" induced a significant increase in polyphenol concentration and oil stability. Fernandes-Silva et al. [16] found a strong relation (*r*<sup>2</sup> = 0.715; *p* = 0.033) with TP and between water stress integral (WSI). Similarly, Pearson's correlation coefficients between oxidative stability (OS) and TP was high and significant (*p* = 0.026), but no significant correlation was found between OS and TC (*p* = 0.322). Moreover, Gómez del Campo [110] and García [117] observed that the application of RDI in summer produced a significantly higher OS, which coincided with a significantly higher content of TP derivatives. These compounds are of great interest because they influence the quality and the palatability of VOO and increase their self-life time by slowing the formation of polyunsaturated fatty acid hydroperoxides.

Irrigation regimes either equivalent to 30 or 100% of ETc, applied to olive trees, "Cobrançosa" affects significantly the activity of L-phenylalanine ammonia lyase (PAL, EC 4.3.1.5), that is considered as the key enzyme in phenolic biosynthesis, the TP and amount of individual polyphenols [17]. Higher PAL activity, TP and individual polyphenol contents were observed for the rainfed conditions in the first picking date, and decreased with maturation of the olive fruits. Also, this effect was observed for the two irrigation regimes applied. The difference in the PAL activity, TP and individual polyphenol content between the three water regimes, decreases as olives become more mature.

Olive oil fatty acid composition is often not affected by RDI strategies [118], although other studies indicate that irrigation strategies cause small variations in the oleic and palmitic acids [16, 116]. Magliulo et al. [119] reported that olive oil fatty acid composition from two different cultivars ("Frantoio"; "Leccino") was more affected by varietal factors and climatic conditions of the year than by water regimes. Curiously, when cv "Arbequina," is cultivated in warm arid valleys of North Western Argentina, produced a lower content of 18:1 acid in relation to the Mediterranean region [120] and a decrease with increasing temperature during oil accumulation of 2% per °C was found.

DI can also influence the sensory attributes of olive oil. In cultivars such as "Arbequina," which normally has low-phenolic concentrations, DI is beneficial due to the greater polyphenol concentrations. More phenolics contribute to better balanced oils with a more sophisticated pungent and bitter flavor [114].

With regard to the quality attributes of tables' olive, they are also affected by DI strategies. Cano-Lamadrid et al. [121] and Cano-Lamadrid et al. [122] evaluated the quality of table olives ("Manzanilla"), after processing that were previously submitted to three irrigation treatments: FI; RDI1 with moderate stress during pit hardening (soft water stress) and RDI2 with low stress at the end of flowering stage, and moderate during pit hardening. They observed that FI olives had the highest weight and size, and were rounded. Color coordinates L\* and b\* had the highest values in RDI2 olives. Aldehydes and monounsaturated fatty acids predominated in FI olive fruits, while terpenes and polyunsaturated fatty acids predominated in T1 fruits, and saturated fatty acids were abundant in RDI<sup>2</sup> olives. Sensory evaluation indicated that global acceptance was higher for RDI1 olives, with high satisfaction degree among consumers due to fresh olive flavor, crunchiness, and global satisfaction. They argue that both RDIs are effective and can be a good alternative irrigation practice for this cultivar. However, these authors evaluated table olives quality after processing, an evaluation after harvest, that is, before olives processing may be more interesting.

Water deficit effect could increase of PhytoPs content, chemical compounds analogs to prostaglandin, which belong to a novel family of plant effectors, may be related to the enhancement of reactive oxygen species (ROS) production under drought stress, which induce the formation of an array of lipid peroxidation products [123]. The phase II of fruit growth can be noncritical considering fruit yield or fruit size [124] but is clearly critical for PhytoPs formation. Thus, olive table trees under RDI can be considered as complementary actions to enhance the PhytoP content and hence their potential beneficial effects on human health as they play a role in regulation of immune function [125].
