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The effect of water deficit on photochemical parameters, hydraulic properties, phytochemical composition and radical scavenging activity were studied on four Olea europaea cultivars (Chetoui, Ouesl...

Hydrogels have a large interest for commercial application in agriculture. Our experiment was performed under greenhouse conditions, to examine the effect of the hydrogel “stockosorb-660” (TS) compared with non treated plants (TC). As compared to TC treatment, the hydrogel treatment increased clearly the growth responses, photosynthetic pigments, the dry weights and the relative water content of olive plantlets mainly in chemlali cv and under drought stress. Under drought stress, the chlorophyll fluorescence measurements were about 0.53 and 0.36 for chemlali and chetoui cultivars, respectively using TS treatment. In the same treatment, as compared to control plantlets, total phenols decreased damages under drought stress and were about 53.94 mg g−1 GAE and 57.37 mg g−1 GAE for chemlali and chetoui cultivars, respectively. Our results confirm also that “stockosorb” hydrogel is a cultivar dependent and seems to be probably suitable for agricultural use because of its capacity to avoid dehydration damages of young olive plants.

Predicting photosynthetic production in olive trees is a key feature in managing the effect of climate change on arid areas. Functional-structural plant modelling is a promising tool for achieving this goal. We used a photosynthetic sub-model that accounted for water and temperature stress and implemented it into LIGNUM model. We then conducted an experiment to validate the model at the leaf level using olive trees (Olea europaea) grown under various climatic condition. Then, we simulated photosynthetic production of three static olive tree models aged 1, 2, and 3 years. Results revealed a good fit between observed and predicted photosynthesis, with coefficient of determination (R2) values of 0.94 and 0.93 for Chemlali and Zarrazi cultivars, respectively. These results showed that the impact of water stress on photosynthetic production was marginal.

Arbuscular Mycorrhizal Fungi (AMFs) are known as a symbiotic microorganism which ameliorates growth and tolerance against stressful conditions of their host plants. It is characterized by morphological, physiological and biochemical events that are controlled by the interaction of both plants and fungus. The aim of this research was to evaluate the intensity (M%) and the Arbuscules abundance (A%) of mycorrhizal infection with Glomus intraradices in olive (Olea europaea L.) tree roots of five Tunisian local cultivars (cvs Oueslati, Meski, Jarboui, Chemlali and Chetoui). After 2 weeks of acclimatization in a greenhouse, the olive plantlets were inoculated with “G. intraradices”. The estimate of percentage of root colonization was calculated using an adequate method. This method consists of putting fragments of colored roots from each cultivar and observing them in a light microscope. These fragments were noted in a grid based on a scale class. Differences obtained in values were detected in all cultivars. This paper suggests the presence of cultivar-dependent differences in both the M% and A% that can be modified by AM fungi as well as by its interaction with olive roots. Results confirm also that oueslati cv has the best compatibility with G. intraradices. These findings open up many opportunities for mycorrhiza inoculation in the oleaster plants production in Tunisia. Key words: Olea europaea L., Glomus intraradices, arbuscules, Oueslati cv.

The impact of intercropping with two different forage crops (legume and grass) on the shoot growth, ion accumulation and some physiological traits of 3-old year olive trees irrigated by high-salinity water (120 mM NaCl) was assessed under greenhouse conditions. Olive plants were subjected to one of the following treatments: TC (control); TG – olive plants intercropped with grass (Oats: Avena sativa L) and TL – olive trees intercropped with legume (Berseem Clover: Trifolium alexandrinum L). Results showed that sodium root:leaf ratio and nitrogen concentration in olive leaves were significantly increased in TL treatment. Olive shoot length and maximum quantum yield of photosystem II (Fv/Fm) were significantly improved by using Berseem Clover as a cover crop. Negative correlation was observed between the total chlorophyll content and the leaf Na+ concentration. On the other hand, polyphenol content was significantly increased in olive leaves when oats were used as cover crops, in relation to the high N-deficiency observed in olive leaves of TG treatment.

Aim: Despite its therapeutic value almost nothing is known about potential adverse health effects of Olea europea L. We therefore investigated the in vitro toxicity and genotoxicity of leaf extracts of this plant. Material and Methods: Extracts from olive tree leaves were obtained from four different regions in Tunisia. We investigated the in vitro toxicity, genotoxicity and antigenotoxicity of their aqueous extracts using the neutral red (NR) uptake, Vitotox and alkaline comet assays. Results: None of the extracts were found to be toxic and none of them were genotoxic, although some doubt exists for the extract obtained at Meski (North of Tunisia). On the basis of the Vitotox test only, none of the extracts appeared to have antigenotoxic (or cogenotoxic) properties. Discussion: The negative genotoxicity underline the safe use of the leaves, for example, as hypoglycemic and antidiabetic preparations. Lack of antigenotoxicity may indicate that the previously reported anticancer effects do not result from protection against genotoxicity. HIGHLIGHTS We investigated the in vitro toxicity and genotoxicity of aqueous extracts of olivesThe neutral Red Uptake test, Vitotox and alkaline comet assay were usedLeaf extracts from 4 different origins were investigatedNone of them showed in vitro toxicity or genotoxicityThe extracts also didn’t have antigenotoxic properties Abbreviation list: BaP: benzo(α)pyrene, EMS: ethyl methane sulfonate, LMP: low melting point, NI50: 50% inhibition of NRU, NR: neutral red, NRU: neutral red uptake, OD: optical density, PBS: phosphate buffer saline, SDS: sodium dodecyl sulphate, S/N: signal to noise ratio, 4NQO: 4-nitroquinoline oxide

The use of wastewater (WW) provides a reliable source of water and nutrients for crop production. Soil tillage is one of the key soil management practices in agricultural land use. In the present study, we studied the effects of these two agricultural practices on key physiological parameters of olive trees and on olive oil quality. The experiment was carried out on mature olive trees (Olea europaea L. cv. Chemlali). Two tillage practices treatments (Trees grown in Tilled soil: TTS; and Trees grown in No-tilled soil: TNTS) were combined with two irrigation treatments (Trees irrigated with WW: IT; and Trees grown under rainfed condition: TRC) during two successive years (2013 and 2014). Statistical analyses demonstrated that the factor “soil tillage” was more efficient in improving photosynthetic parameters of olive trees than WW irrigation. The combination of soil tillage with WW irrigation improved significantly leaf chlorophyll fluorescence parameters, stomatal conductance, transpiration and chlorophyll content, which closely associated with an increase of photosynthetic rate, and a decrease of stress metabolites (leaf phenolic compounds and carbohydrates). On the other hand, a decrease of key photosynthetic parameters and an accumulation of stress metabolites in leaves were observed when combining rainfed condition and No-tilled soil. WW irrigation affected negatively the oxidative stability and nutritional value of olive oil, especially by decreasing the contents of antioxidant compounds (total phenols and pigments) and the levels of MUFA, C18:1, C18:3 and elevating SFA and PUFA contents. However, soil tillage combined with TRC improved oil stability to oxidation and its nutritional value by increasing the contents of antioxidant compounds and the levels of MUFA and C18:1, as well as C18:1/C18:2 and MUFA/PUFA ratios. The results of this study prove that, under water scarcity conditions, wastewater irrigation in oleiculture should be combined with soil tillage and recommended only in the ‘Off’-year to support vegetative growth and improve physiological performance of olive trees. In the ‘On’-year, tilling the soil under rainfed conditions proved to be the most favorable cropping strategy for enhancing both physiological performance of olive trees and olive oil quality. These findings must be taken into consideration when developing strategies for oil quality enhancement, mainly in an exporting country like Tunisia.

Olea europaea L. is one of the most important fruit trees in Tunisia because of its content of many potentially bioactive compounds. The aim of this study was to evaluate the chemical composition, antibiofilm, antiradical and acethylcholinesterase inhibitory activities from four Tunisian cultivars of Olea europaea L., i.e. 'Chetoui', 'Meski', 'Oueslati' and 'Jarboui'. By means of standardized methods, total phenols were determined and some of them characterized by HPLC. The total phenols and flavonoids contents were found to be the highest in the leaves of Chetoui cultivar. The Chetoui cultivar exhibited an important antioxidant and anticholinesterasic activity and an important anti-biofilm activity against Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus cereus, Candida albicans, Enterococcus faecalis and Escherichia coli, with percentages of inhibition comprised between 83 and 93% at 2xMIC values. Olive leaves extracts could be used in the control of bacterial biofilms in food and food-related environments.

Compost, olive mill wastewater and legume cover crops combined with complementary irrigation by saline water were tested under field conditions during 2016 and 2017 cropping seasons (‘Off’ and ‘On’ years respectively), in an organic mature olive grove cv Chemlali, grown at a density of 100 trees. ha-1. The experiment was conducted with four agronomic practices (TC-no amendment; TP-olive trees amended with compost, TM-olive trees amended with olive mill wastewater and TL-olive trees intercropped with legumes) factorially combined with two irrigation treatments (NI: non-irrigated olive trees and IR: olive trees irrigated with saline water of 4 g.l-1). The complementary irrigation by a limited quantity of saline water (4 m3.tree-1 per season) applied during the fruit growth (May-September) increased significantly the soil water content (SWC) mainly in the plot amended with compost. In both irrigated and rain-fed plots, the soil electrical conductivity (SEC) increased significantly during the dry season mainly in the control and the plot amended with olive mill wastewater (OMWW). Under rain-fed conditions, leaf sodium contents decreased by about 30 and 50%, respectively in olive trees amended by compost and those intercropped with legumes. Complementary irrigation with saline water increased leaf sodium levels in all plots, mainly in trees amended with OMWW, by about 40% compared to those of OMWW plot grown under rain-fed conditions. The level of leaf nitrogen increased by the application of both soil organic amendments and irrigation, while leaf phosphorus level was only affected by irrigation salinity, except for trees intercropped with legumes. Shoot growth, oil yield and fruit pomological characteristics were significantly improved either by the soil organic amendments or by the complementary irrigation. Nevertheless, phenol contents in fruits and in olive oil were significantly affected by compost and irrigation with saline water. Intercropping olive trees with legumes enhanced phenol contents in fruits and olive oil.

Abiotic stresses present a real environmental problem in agriculture field. In our paper, we examine the significance of arbuscular mycorrhizal fungi (AMF) and soil amendment with water retaining superpolymers (hydrogel) on growth and physiology performance of olive plantlets. Our experiment was carried out in nursery conditions, to test the impact of hydrogel (TH) and mycorrhizal fungi (TM), used individually or combined (THM), and compare them with non inoculated plants (TC), to understand and reduce the water stress damage in olive plantlets (cv. Chemlali). We also evaluate interactions between hydrogel, mycorrhizal treatments and water regimes. Results of mycorrhization (M%) show that roots colonized by Rhizophagus irregularis of well-watered plants were about 40.87%. In combined treatment (THM), M% was about 32.14%. Compared to TC treatment, TM treatment enhances significantly the dry weights of the whole plant under the two water regimes. The TM treatment had the highest relative water content (66.50%) and Chl (a + b) (0.83 mg g− 1) in stressed conditions. We found also that under water stress, the maximal quantum efficiency of the photosystem II measurements in leaves were significantly improved by 50.70% in TH treatment compared to control. For phenolic contents, TH treatment decreased significantly total phenols by 50.10% compared to TC. Our study gives evidence that the use of AMF and the hydrogel separately or in combination may enhance the capacity to avoid drought damages of olive plantlets and improve olive performances.

We studied changes in morphology, sclerophylly, chlorophyll photosynthetic parameters and total phenol contents in leaves of three olive (Olea europaea L.) cultivars; Oueslati, Jarboui and Meski which grew under water deficit conditions. Our results showed significant differences in trichome and stomatal densities, area of the leaf and relative surface of stomatal pores. The photosynthetic parameters Fv/Fm, Phi PSII and ETR were negatively affected by the water deficit in these three varieties. The total phenolic and flavonoid contents increased in all cultivars, with Oueslati showing the highest values. The Oueslati variety could be considered as the most drought-tolerant compared to Jarboui and Meski. Therefore we believe this cultivar is the most suitable for cultivation in semi-arid environments. (c) 2018 SAAB. Published by Elsevier B.V. All rights reserved.

The effects of salinity, on three olive tree cultivars (‘Picholine’, ‘Meski’ and ‘Ascolana’), growing under greenhouse conditions, were studied through the following parameters: vegetative growth, stomatal density and ion accumulation (Na + , K + , Ca 2 + , and Cl − ). Olive plants were subjected to three saline irrigation treatments: T0 (irrigated with tap water), T1 and T2 irrigated with 6 and 9 g of NaCl·l 1 solution respectively. As salinity increased, vegetative growth, stomatal density, root dry weight and root density of ‘Meski’ and ‘Ascolana’ declined sharply. Sodium accumulation was greater in leaves and roots with increased external NaCl concentration, but differently according to cultivars. In fact, Na + concentration was higher in leaves than in roots for ‘Meski’ and ‘Ascolana’ cultivars. However, for ‘Picholine’ the highest content of Na + was in roots. Generally, ‘Picholine’ accumulate less Na + in leaves and were able to maintain higher K + /Na + ratios compared to other cultivars. In leaves, ratios of K + /Na + and Ca 2 + /Na + between cultivars were lower in salinity treatments compared to control. ‘Meski’ and ‘Ascolana’ have a higher power of water desalination than ‘Picholine’.

The present work was aimed at evaluating, under natural situations (field of olive trees, Olea europea cv Chemlali), the effects of one-year agronomic application of an olive mill wastewater (OMW) biologically derived compost. The experimental study was carried in 2014 in an olive orchard situated at Jammel (region of Monastir-Tunisia). An experimental plot (TM, 50 olive trees) was amended on February 2014 (the 'Off year) with 50 m 3 /ha. The plot TC (50 olive trees) was not amended and served as a control. After one year of OMW application, at harvest, olive fruits were collected and pomological characteristics were determined. Olive oil was extracted and biochemical parameters were studied. Statistical analyses showed that short-term field application of OMW affected negatively carpometric characteristics of olive fruits and oil content. Oil produced from TM had a decreased pigment content and oxidative stability. Moreover, the level of MUFA, particularly oleic acid, as well as C18:1/C18:2 and MUFA/PUFA ratios were negatively influenced by OMW amendment which affects negatively olive oil quality and nutritional value. These findings must be taken into consideration when developing strategies for oil quality enhancement, especially in an exporting country like Tunisia.

Chlorophyll content, fluorescence parameters, xylem hydraulic properties, total phenolic content and antiradical activity were studied on young plants of four Tunisian olive cultivars (Chetoui, Ouslati, Jarboui and Meski) grown under water deficit conditions for two months. Water stress caused a decline in chlorophyll content, in maximum quantum yield of photosystem II (Fv/Fm), in linear electron transport rate (ETR) and in quantum efficiency of PSII electron transport (Φ PSI). Chetoui variety was the less affected by water stress but all these parameters decreases considerably in Ouslati, Jarboui and Meski. In all cultivars, water stress induced an increase in xylem vessel frequency. Water stress also increased the phenolic and flavonoid contents and antiradical activity in all cultivars. Chetoui cultivar may be considered as the most tolerant cultivars among the tested cultivars showing higher phenolic and flavonoid contents and an important antiradical activity under water deficit. Meski cultivar is the most sensitive one.

We evaluated the potential of sap flow values estimated from records with the heat dissipation method for irrigation in an olive orchard (Olea europaea L, cv. Meski) near Enfidha, Tunisia. Trees were cultivated at 7 × 7 m spacing. Two drip irrigation treatments were imposed using the sap flow and the FAO methods. The two treatments were irrigated by 100% of crop evaptranspiration (ETc). T1: ETc measured by the sap flow method and T2: ETc estimated by the FAO method. Sap flow, leaf and stem water potentials, leaf photosynthetic activity, stomatal conductance and transpiration rate were recorded in representative trees from both treatments, during the full irrigation season from April to August. Results showed that the irrigation dose calculated from T2, based on FAO method compared to the T1, based on sap flow decreased by about 25%. Under T1 irrigation scheduling strategy, the daily transpiration decreased by 20% and consequently the water potentials were decreased significantly. Infect, olive trees under T1 were moderately stressed and subsequently leaf gas exchange parameters were affected by about 15%. Key words: Sap flow, water potential, leaf photosynthetic activity, olive tree, Olea europaea irrigation scheduling.

Here, we report the characterization of virgin olive oil samples obtained from fruits of the main Tunisian olive cultivar (Chemlali) grown in four planting densities (156, 100, 69, and 51 trees ha(-1)). Olive oil samples obtained from fruits of trees grown at 100 trees ha(-1) had a higher content of oleic acid (65.5%), a higher content of chlorophyll and carotenoids, and a higher content in total phenols (1059.08 mg/kg). Interestingly, olives grown at the two highest planting densities yielded more stable oils than olives grown at the two lowest ones. Thus planting density is found to be a key factor for the quality of olive oils in arid regions.

The olive oil content in phenolic compounds depends on the variety of the fruit used for its extraction as well as on the predominant climate conditions in the tree cultivation area. Here, we report on the characterization of virgin olive oil samples obtained from fruits of the main Tunisian olive cultivars Chemlali and Chetoui, grown in three different Tunisian locations, Zaghouan (North), Sousse (Center) and Sfax (South). Chetoui olive oil samples obtained from fruits of olive trees cultivated in Zaghouan and Chemlali olive oil samples obtained from fruits of olive trees cultivated in Sousse were found to have a higher mean total phenol content (1004 and 330 mg/kg, respectively). Olive oil samples obtained from fruits of both cultivars had different phenolic profiles and a higher content in 3,4-DHPEA-EDA when the olive trees were cultivated in Zaghouan. Both olive cultivars were found to have different responses to environmental conditions. Chetoui olive oil showed decreased oxidative stability when the fruits were obtained from olive trees cultivated in the center of Tunisia (34.8 h) and in Sfax (16.17 h). Furthermore, statistical data showed that the phenolic composition and oxidative stability of Chetoui olive oil varied more by location than those of Chemlali olive oils.

Differences in abscisic acid (ABA) accumulation between two olive cultivars were studied by enzyme-linked immunosorbent assay in roots and leaves, leaf water potential (Ψl), stomatal conductance (g s) as well as photosynthetic rate (A) were also determined in well-watered (WW) and water-stressed (WS) plants of two olive cultivars ‘Chemlali’ and ‘Chetoui’. ‘Chemlali’ was able to maintain higher leaf CO2 assimilation rate and leaf stomatal conductance throughout the drought cycle when compared with ‘Chetoui’. Furthermore, leaf water potential of ‘Chemlali’ decreased in lower extent than in Chetoui in response to water deficit. Interestingly, significant differences in water-stress-induced ABA accumulation were observed between the two olive cultivars and reflect the degree of stress experienced. Chemlali, a drought tolerant cultivar, accumulated lower levels of ABA in their leaves to regulate stomatal control in response to water stress compared to the drought sensitive olive cultivar ‘Chetoui’ which accumulated ABA in large amount.

Leaf structural adaptations for the reduction of water loss were examined in two olive (Olea europaea L.) cultivars (Chemlali and Chetoui) growing under water stress conditions. Leaf measurements included leaf tissue thickness, stomatal density, trichome density, specific leaf area, leaf density, water relations, and gas exchange. We found considerable genotypic differences between the two cultivars. Chemlali exhibited more tolerance to water stress, with a thicker palisade parenchyma, and a higher stomatal and trichome density. Chemlali leaves also revealed lower specific leaf area and had higher density of foliar tissue and lower reduction in net CO2 assimilation rate. The mechanisms employed by these two cultivars to cope with water deficit are discussed at the morpho-structural level. The morphological and structural characteristics of the leaves are in accordance with physiological observations and contribute to the interpretation of why the olive cv. Chemlali is more drought-tolerant than cv. Chetoui. Furthermore, from the behaviour of Chemlali plants we consider this cultivar very promising for cultivation in semi-arid areas.

This research, aimed at evaluating stress on the olive tree, utilized cultivars ‘Meski’ and ‘Chetoui’ in regards to the removal of major elements such as nitrogen (N), phosphorus (P), magnesium (Mg...

The comparative responses of two young olive trees (Olea europaea L. ‘Chemlali’ and ‘Chetoui’) to drought stress were investigated during 1 month. Three-month-old own-rooted plants were subjected to two irrigation treatments: WW (well watered plants that were irrigated with fresh water to maintain a soil water content close to field capacity), and WS (water stressed plants by withholding water). Leaf water potential, gas exchange and leaf lipid composition were studied. ‘Chemlali’ was able to maintain higher leaf CO2 assimilation rate and leaf stomatal conductance throughout the drought cycle compared to ‘Chetoui’. Water stress induced a larger decrease in the total lipid content in ‘Chetoui’ than in ‘Chemlali’. Interestingly, the constitution of different lipid classes was highly altered in ‘Chetoui’. Lipid changes in Chemlali, a drought tolerant cultivar, revealed more stability of its cellular membranes to drought stress as compared to the drought susceptible olive cultivar, Chetoui. Furthermore, in comparison to the controls, drought stressed plants showed an increase in the degree of unsaturation of leaf lipids in the two olive cultivars. Moreover, the results observed in Chemlali showed that besides changes in lipids composition this cultivar may have an efficient defence strategy which can be related on antioxidative production against oxidative stress.

The present study focused on the comparison the chemical composition of virgin olive oil samples obtained from fruits of the main Tunisian olive cultivar (Chemlali) grown in four planting densities (156, 100, 69, and 51 trees ha−1). Despite the variability in the triacylglycerols and volatile compounds composition, the quality indices (free fatty acids, peroxide value, and spectrophotometric indices K232and K270) all of the virgin olive oils samples studied met the commercial standards. Decanal was the major constituent, accounting for about 30% of the whole volatiles. Moreover, the chemical composition of the volatile fraction of the oil from fruits of trees grown at the planting density of 156, 100, and 51 trees ha−1was also characterised by the preeminence of 1-hexanol, while oils from fruits of trees grown at the planting density of 69 trees ha−1had higher content of (E)-2-hexenal (20.3%). Our results confirm that planting density is a crucial parameter that may influence the quality of olive oils.

The objective of this work was to assess the pollen viability, the pollen capacity (germination and tube growth) and the rate of fruit set in 19 cultivars of olive trees field-grown in Chott Mariem (Tunisia) after self-and free-pollination treatments during two seasons 2012 ('on'year) and 2013 ('off ’year). The pollen viability ranged from 60.5% for ‘Meski ’to 88.85% for ‘Gerboui ’during 2012 ('on'year) and between 97.47% for ‘Chetoui ’to 62.38% for ‘Meski ’in 2013 ('off ’year). All the cultivars increased their values of viability and germination during 2013 comparatively to 2012, with important consequences on the fertilization process measured by the initial fruit set rate. Concerning the pollination treatments, generally, the free-pollination improved fruit set when compared with self-pollination, especially for ‘Meski ’. However, a non-pollination of ‘Ascolana ’and ‘Tounsi ’was observed with all pollination modes and during the two years in Chott Mariem. Our results showed a high correlation between the rate of fruit set after self-and free-pollinations during the two years of study 2012 and 2013 (respectively, r2= 0.74 and 0.65). This study highlights some major remarkable differences among cultivars in terms of pollen abilities. In general, concerning the pollination efficiency of olive cultivars, the pollen viability can be an important characteristic to be considered as an indicative parameter of pollen development and functionality. Finally, this is a topic of particular importance for large-scale isolated plantings and in choosing the cultivars in new olive groves plantations.