Variability of olive plant species regarding the key olive oil quality components

Abstract

Virgin olive oil (VOO) represents the primary dietary lipid source in the Mediterranean diet and has been linked to its positive health benefits. VOO metabolites responsible for its nutritional and organoleptic quality include certain components that are transferred almost unchanged from fruit to oil (fatty acids and tocopherols) and other compounds that are synthesized during the oil extraction process by endogenous enzymes from precursors already present in the fruit (volatile and phenolic compounds). The health - promoting characteristics of VOO seems to be related to the high level of oleic acid, an adequate balance of saturated/unsaturated fatty acids, the presence of tocopherols and, specially, the contents of phenolic compounds. Meanwhile, volatile compounds are responsible for its aroma, whereas phenolic compounds are also responsible for the bitter and pungent taste notes of this oil. The final content of these metabolites related to VOO quality is controlled by the levels of expression/activity of the corresponding genes/enzymes involved in their biosynthesis which are cultivar dependent. Given that oil quality is one of the main objectives of the breeding programs aiming at obtaining new olive cultivars, knowledge of the content of these key components for the VOO quality might be very useful for the selection. Moreover, the combination of biochemical and molecular studies would allow to identify the most important genes/enzymes in relation to the oil quality and to know their regulatory mechanisms, so that this knowledge may be used in the molecular marker assisted selection of olive clones with improved oil quality features. For this purpose, the natural variability of the olive species was assessed in a collection of cultivars from the World Olive Germplasm Bank (WOGB) located at Córdoba, and the progeny of a cross of Picual x Arbequina olive cultivars. Analytical data showed that the cultivar collection displayed, in general, a higher level of variability than the progeny cross for most of the metabolites assessed, and that a single cross of olive cultivars might apparently provide enough degree of variability for most of the oil quality traits sought in a breeding program.