Olive fruits have a round to ovoid shape, and their weight ranges from 0.5 to 20 g, with most falling within the range of 2–8 g. Their characteristic strong bitter taste, due to the presence of oleuropein, decreases with fruit ripening, as the peel colour changes from green to yellow, purple and finally black. The principal chemical components of olive fruit pulp are water (60–75%), lipids (10–25%), reducing sugars (2–5%) and phenols (1–3%). Morover, olives have significant amounts of sterols and flavonoids such as tocopherols, carotenoids and minerals. Table olives have important nutritional value due to their richness in monounsaturated fatty acids, vitamin E and phenolic compounds.

In this section

1.4.1. Fruit size, shape and flesh to stone ratio

1.4.2. Fruit detachment force

1.4.3. Bruising
 

Salinity is one of the most important environmental factors affecting plant growth and productivity, particularly in arid and semi-arid regions of the world. The negative effects of salinity are associated with a reduction in water availability in the soil solution and the accumulation of specific ions in the leaves. This is a serious problem since the salinisation of arable lands is increasing throughout the world.

Salinity effects depend on the salt concentration and plant tolerance. In this sense, the olive is considered a moderately salt-tolerant plant that may be cultivated in saline soils where other fruit trees cannot grow. The olive may develop well with a minor reduction of yield with an electrical conductivity (EC) of the saturated soil extract ranging from 4 to 6 dS m^-1. In soils with high calcium, like those rich in gypsum, these values could be increased in 2 dS m^-1. Salt tolerance, however, is a cultivar-dependent characteristic.

Even at low contents of total soluble salts, plant growth can be affected by the excess of some specific ions in the soil solution, particularly chloride, sodium and boron. The olive is very tolerant to an excess of chloride, so this ion does not represent a problem in olive culture. In fact, KCl or CaCl₂ can be used without any problem in olive cultivation. Excess sodium may negatively affect both the soil and the plant. Exchangeable sodium percentage (ESP) in the soil above 15% causes a general deterioration of soil structure resulting in poor soil aeration and reduced permeability.

Verticillium wilt of olive, caused by the soil-borne fungus Verticillium dahliae Kleb., is globally the most important disease affecting this crop. Over recent years, this fungus has led to the demise of thousands of olive trees across the world. The situation is exacerbated by factors such as susceptible cultivars, irrigation practices and planting on soil that was previously planted with host crops like cotton or tomato (Montes-Osuna and Mercado-Blanco, 2020).

Given the absence of efficient chemical solutions, the vulnerability of popular olive cultivars, and the persistence of the fungus in the soil, there has been a significant effort to identify resistant cultivars. This is seen as a cornerstone in a holistic approach to managing the disease (López-Escudero and Blanco-López, 2007).

Anthracnose is the most critical fruit disease affecting the olive crop. Eighteen species of the genus Colletotrichum (mainly C. godetiae, C. nymphaeae, and C. acutatum) have been associated with this disease in most olive-growing regions, including non-Mediterranean areas (reviewed by Cacciola et al. 2012; Talhinhas et al., 2018; Moral et al., 2021; Moreira et al., 2021; Garcia-Lopez et al., 2023). The disease has two syndromes: fruit rot (also known as “soapy rot”) and the dieback of branches. In addition, oils coming from affected olive fruits display substantial chemical and organoleptic defects (Leoni et al., 2018; Moral et al., 2014)

Olive scab disease, also called peacock’s eye, peacock spot or leaf spot, is caused by the ascomycete fungus Venturia oleaginea and is the most important foliar disease of olive (Olea europaea) in many olive-growing regions, including southern Spain. The pathogen mainly attacks the adaxial surface of the olive leaf, causing typical scab lesions that are often surrounded by yellow haloes leading to premature leaf drop (Figure 1). Lesions can also occur along the main vein on the abaxial leaf surface and on leaf petioles, fruits, fruit peduncles and young shoots (Figure 2). The dark colour of the lesions is due to the production of asexual spores or conidia, which are the only inoculum causing infections, since the fungus lacks a sexual stage that produces ascospores. Heavy defoliation usually follows severe infection, and recurrent infections cause branch dieback and tree weakness. Most infected leaves and fruit fall to the ground (Figure 3). Olive oil obtained from fallen fruits is of poor quality because various saprophytic fungi colonise the fruit and change the acidity and organoleptic characteristics of the oil. The disease is particularly severe in nurseries and in orchards that are densely planted with susceptible olive cultivars when environmental conditions are favourable.

This monophagous tephritid poses the greatest arthropod threat to olive cultivation, with Australia being the only Bactrocera oleae-free (B.oleae) zone within the global olive-growing area. The brown-yellowish thorax of the adult flies, with 2 to 4 parallel grayish bands, and the hyaline wings with a brownish spot at the apex, are the most important B. oleae morphological features. The eggs are creamy white, and larvae are white-yellowish, growing from 1 mm at L1 to 7-8 mm at L3 with the pupa confined inside the puparium.