Genetic and Environmental Features for Oil Composition in Olive Varieties
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OCL 2014, 21(5) D504 c A.J. Bervillé, C.M. Breton, Published by EDP Sciences 2014 OCL DOI: 10.1051/ocl/2014007 Oilseeds & fats Crops and Lipids Available online at: www.ocl-journal.org Research Article –Dossier Open Access OLIVE OIL Huile d’olive Genetic and environmental features for oil composition in olive varieties André Jean Bervillé1 and Catherine Marie Breton2,, 1 INRA, UMR DIAPC, 2 place Viala, Bât 33, 34060 Montpellier Cedex 2, France ossier 2 INRA, UMR-AGAP, équipe Davem, campus Supagro, Bat 21, 34060 Montpellier Cedex 1, France D Received 21 January 2014 – Accepted 13 February 2014 Abstract – Consumption of olive oil helps both prevent and cure heart disease. Olive oils vary in their fatty acid profiles as well as those of other secondary metabolites (phenols, sterols, and terpene compounds). We seek to distinguish the genetic bases from the environmental factors that cause these variations. The genetic base is indeed wide: varieties originate in different domestication occurrences, from different oleaster trees and in differing climatic regimes. With the aid of diagrams, we set out briefly the oil synthesis pathway for fruits in comparison with that of seeds, and the specific aspects of olive oil in particular. Varieties of olive have appeared that are adapted to regions with harsh conditions where the oleaster could not thrive. Environmental stresses have consequences on drupes and their oil profiles; these have been highlighted in European countries through the use of appellations. Whilst stresses tend to enhance the quality of the end product, they do however decrease final yields with potential negative impacts on olive growers’ incomes. Irrigation experiments are underway in order to determine the optimal amount of watering. In breeding new varieties, the result sought is that of accumulating pest tolerances and fruit-quality characteristics; selection programmes are however expensive as they necessitate observations over many years. Consumers have choice across a range of appellations with different organoleptic specificities at different prices, and whatever the appellation of the oil they can expect a positive effect on their health. Keywords: Abiotic stresses / appellations / diversity / health / oil profiles / phenolic compounds Résumé – Les caractéristiques génétique et environnementale de la composition en huile des variétés de l’oli- vier. L’huile d’olive est bénéfique pour prévenir et guérir les maladies cardiovasculaires. Les profils de l’huile d’une variété sont variés tant pour les acides gras que pour les métabolites secondaires (composés phénoliques, stérols, et terpéniques). Notre but est de séparer les causes génétiques des causes environnementales qui supportent les variations des profils de l’huile. Les bases génétiques sont larges puisque les variétés sont issues d’événements de domestication distincts à partir de l’oléastre qui proliférait sous des climats différents. Nous exposons succinctement les spécificités de l’huile d’olive ainsi que les principales voies métaboliques pour les fruits par comparaison aux graines. Nous avons choisi de comparer les profils par des diagrammes. Des variétés adaptées à des stress sévères sont apparues où l’oléastre ne peut se maintenir. Les stress environnementaux ont des effets sur le fruit pour la conserve et sur le profil de l’huile, ce qui a été valorisé par les appellations dans les pays européens. Si le stress favorise la qualité des produits, il diminue en revanche le rendement et par là, le revenu des oléiculteurs. Des essais expérimentaux sont en cours pour déterminer le niveau d’irrigation sans diminuer la qualité des produits. La sélection de nouvelles variétés d’olive a pour objectif de rassembler des tolérances aux ravageurs et la production de fruits de qualité, néanmoins, les essais sont très coû- teux pour des arbres observés plusieurs années. Les consommateurs ont le choix parmi de nombreuses appellations des produits, et quelle que soit l’appellation l’effet favorable de l’huile d’olive sur la santé est attendu. 1 Introduction the colonization period (16–18th centuries) all the regions of the world with a similar Mediterranean-type climate ex- Olive trees have been growing throughout the Medi- perienced planting by Spanish, Italian or French settlers. It terranean basin for between six and seven millennia. During has been domesticated as the Oleaster (Besnard et al., 2002; Present address: Institut des Sciences de l’Évolution de Montpel- Breton, 2006; Breton et al., 2006; Breton and Bervillé, 2013) lier (ISE-M), UMR CNRS 5554, place E. Bataillon, cc63, Bât 24, 1er and its cultivation has spread to regions where the wild olive étage, 34095 Montpellier Cedex 5, France tree (oleaster) cannot thrive. They are grown for oil and Correspondence: [email protected] This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A.J. Bervillé, C.M. Breton: OCL 2014, 21(5) D504 canned fruit production; very little cultivation has a decorative 2012; Visioli and Galli, 2000). The composition of olive oils purpose. varies widely depending on the varieties and the regions where At present, most olive varieties are diffused as a clone. In they are grown. European regulations limit the use of the term a clone all the trees (each tree is a further ramet) are obtained “olive oil” to olive oil having an oleic acid content (OAC) by cuttings or by grafting from the initial tree (itself named the greater than 55% (Regulation ALINORM 01/17 2001). Olive ortet). No genetic variation exists therefore between the ram- oil categories are consequently based upon taste and on pro- ets of each ortet. All variations in the final product are con- cesses employed to press the drupes (Regulation 299, 2013), sequently attributable to environmental and physical factors but not on the fatty acid profile. The fatty acid profile deter- – soil composition, temperature range, rain regime – and the mines the fluidity of the oil. However, in the oleaster the ob- fruit processing methods employed – mill stone, mill hammer, served range in OAC is lower than in the crop (Hannachi et al., crushing temperature, centrifugation, filtration, and oil stor- 2008) – some oleaster trees may produce an olive oil with an age conditions. The mechanisms underlying environmentally- OAC lower than 55%. caused variations in oil composition are for the most part To understand the genetic trends in olive oil composition, unknown. we consider first the transition phases – probably during the Why is it important to determine the relative importance period from the Mesolithic to the Neolithic – from natural of genetics and environmental factors? The obtention of cer- populations of oleaster tree to the first land races population tain type of end-products (the fatty acid profile, for example) varieties of the olive that may have occurred. Six to seven mil- depends mainly on genetic factors, whereas the organoleptic lennia of selection have given rise to a huge variability in fruit quality of an oil depends mainly on environmental factors such shapes and size, oil content and oil composition. Among all the as drought stresses. compounds of the oil, those that have direct observable conse- An initial source of diversity in oil results from the diver- quences – the taste, for example – would be screened more sity in domesticated oleaster trees. The genetic components of rapidly than those with indirect effects – such as antioxidant olive varieties affect the composition of the oil – alleles of the activity or the prevention of ill-health. We hypothesize that main genes that direct oil synthesis pathways, alleles that di- during the early stages of the olive’s domestication process, the rect the synthesis of phenolic compounds synthesis and like- oil extraction technology was poor and that fruits were prob- wise that of other secondary metabolite compounds (sterols ably crushed with other raw materials and released as oil into and terpenoids) found in the oil fractions. Each variety, then, pots for cooking cereals and vegetables. displays a specific broad composition of compounds which, The natural selection of oleaster trees has probably during the various stages of the fruit’s maturity, may be more favoured those that are most attractive to small mammals and or less affected by environmental parameters. A further source birds. We consider it likely that the oil composition profile has of diversity lies in the unconscious selection on the part of an effect on the fruit’s attractiveness to humans, and we will olive growers for trees that produce the type of oil that they advocate this aspect further. personally favour. Finally, the drupe is affected by the choice of The processes of domesticating the oleaster that led to the canning processes, just as the oil is by the method employed to olive trees obviously started on common oleaster trees, but hu- extract it from the drupes. We therefore examine here the con- mans will have unconsciously screened for trees that yielded sequences of genetic and environmental features on the cur- enough fruits, with high oil content, and with stable oil com- rent olive varieties and the trends in the breeding of new olive position after harvest. varieties. Once the methods to separate the oil from the pulp became widely known (probably by the bronze age, Riley, 2002) new ortet trees with higher oil content or greater ease of oil extrac- 2 Causes of variation from past to present tion were unconsciously screened for. Subsequently, all com- times in olive oil pounds that could positively interact with the oil’s long shelve storage become important in the oil composition, and again In the 19th century drupes were not only used as a source these will have been screened for unconsciously. of food, but also as an industrial lubricant.