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Accueil du site → Doctorat → Grèce → Effects of pre- and postharvest treatments with growth regulators on olive (Olea europeae L.) fruit. : physiological and biochemical processes in relation to quality

Agricultural University of Athens (2014)

Effects of pre- and postharvest treatments with growth regulators on olive (Olea europeae L.) fruit. : physiological and biochemical processes in relation to quality

Kafkaletou, Mina

Titre : Effects of pre- and postharvest treatments with growth regulators on olive (Olea europeae L.) fruit. : physiological and biochemical processes in relation to quality

Auteur : Kafkaletou, Mina

Université de soutenance : Agricultural University of Athens

Grade : Doctor of Philosophy (PhD) 2014

Résumé
The objective of the present study was the evaluation of the effects of different growth regulators on physiological and biochemical processes during ripening of olive fruit. The possible relations of these processes with quality attributes were also investigated. In Chapter 1, physiological and quality attributes during ripening of ‘Koroneiki’ olives were studied in two different growing years. Oil content, fatty acid profile, total and individual antioxidants (phenolic compounds and α-tocopherol) were determined along with respiration and ethylene production rates in olives harvested at different maturity indices. Positive correlations were found among the attributes determined that had similar course of changes during ripening, and vice versa, which could be also related to harvest-timing and to quality attributes. Besides, rates of leaf photosynthesis in combination with sugar concentrations in leaves and fruit were estimated. In leaves, photosynthesis (measured as CO2 assimilation rates) and stomatal conductance were stable during the period of fruit ripening. Glucose and sucrose concentrations showed a decreasing trend in both leaves and fruit. However, fructose decreased and mannitol (MAN) increased in leaves when oil accumulation occurred in fruit. The important role of MAN in oil accumulation was suggested, as also indicated by MAN treatments. In Chapter 2 and Experiment A, the effects of pre-harvest individual applications of abscisic acid (ABA), ethylene-releasing compound Ethephon (ETH) and ethylene synthesis inhibitor ReTain (active ingredient of amino-ethoxyvinyl-glycine or AVG) at various maturity states on oil content, fatty acid profile, total and individual antioxidants were determined in harvested olives during exposure at 20 °C. The main results showed that leaf and fruit drops were observed when ABA and ETH were applied at late states of maturity. During exposure at 20 °C, total phenolics (TP) and total antioxidant capacity (TAC) increased. However, the pattern of changes in individual phenolics depended on each particular compound, whereas there was no effect of exposure time on fatty acid profile. In Chapter 2 and Experiment B, the effects of pre-harvest treatments with growth regulators (1-naphthaleneacetic acid or ΝΑΑ, ΕΤΗ and ΝΑΑ + ETH) in combination with/without girdling on fruit attributes of ‘Koroneiki’ olives were investigated. Fruit were sprayed at dark green state and harvested 1 month later. Treatments with NAA and ETH as well as girdling had no effect on peel color and respiration rates. Ethylene production rates were promoted by ETH treatments. ETH, with/without girdling affected the oil content. NAA, at a low concentration, enhanced TP and TAC values. By contrast, treatments had no consistent effect on fatty acids. In Chapter 3, the effects of post-harvest continuous ethylene application on green ’Konservolia’ olives were evaluated at 20 °C for up to 10 days. In Experiment A of Chapter 3, the effects of a series of ethylene concentrations on peel color and firmness (F) were evaluated. Ethylene prevented fruit red coloration and increased firmness (F). In Experiment B, the effects of ethylene, ethylene synthesis inhibitor AVG and ethylene action inhibitors 1-methylcyclopropene (1-MCP) and silver nitrate (SN) on peel color, F and fruit respiration were evaluated. Ethylene increased F values initially, and thereafter prevented decreases in F values and respiration rates up to day 5. AVG, 1-MCP and SN exhibited contrary to ethylene effects on F and respiration rates.In Chapter 3, the Experiment C was carried out in order to explain the increased F values, as well as changes in phenolic compounds in harvested olives and in response to ethylene treatments. The effects of a continuous ethylene treatment, applied after a treatment with/without 1-MCP, on cell wall characteristics were evaluated. The results showed that the increased fruit F could be rather attributed to the wall rigidity of cells nearest the skin, as also supported by microscopic observations. Furthermore, total and individual phenolics were assessed in Experiment C. In all samples, oleuropein, TP and TAC exhibited similar pattern of changes. Fluctuations observed in the rest phenolic compounds had no consistent trend.

Mots Clés : Olea europeae L. ; Plant growth regulators ; Οlive fruit maturity stages ; Antioxidants ; Fatty acids ; Cell wall components

Présentation (National Archive of PhD)

Page publiée le 19 novembre 2016, mise à jour le 14 mars 2020