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Olive tree (Olea europaea L. subsp. europaea var. europaea) is one of the most important species of the Mediterranean region and one of the most ancient species domesticated. The availability of whole genome assemblies and annotations of olive tree cultivars and oleaster (O. europaea subsp. europaea var. sylvestris) has contributed to a better understanding of genetic and genomic differences between olive tree cultivars. However, compared to other plant species there is still a lack of genomic resources for olive tree popula-tions that span the entire Mediterranean region. In the present study we developed the most complete genomic variation map and the most comprehensive catalog/resource of molecular variation to date for 89 olive tree genotypes originating from the entire Mediterranean basin, revealing the genetic diversity of this commercially significant crop tree and explaining the divergence/similarity among different variants. Addi-tionally, the monumental ancient tree ‘Throuba Naxos’ was studied to characterize the potential origin or routes of olive tree domestication. Several candidate genes known to be associated with key agronomic traits, including olive oil quality and fruit yield, were uncovered by a selective sweep scan to be under selection pressure on all olive tree chromosomes. To further exploit the genomic and phenotypic resources obtained from the current work, genome-wide association analyses were performed for 23 morphological and two agronomic traits. Significant associations were detected for eight traits that provide valuable candidates for fruit tree breeding and for deeper understanding of olive tree biology. info:eu-repo/semantics/publishedVersion

Verticillium wilt resulting from infection by Verticillium dahliae is one of the most devastating soilborne fungi of the olive tree (Olea europaea L.) worldwide. The pathogen infects a wide variety of plants and can survive in the soil for many years, and chemicals cannot control it. Therefore, sustainable disease management strategies are suggested, with the exploitation of host resistance as the most predominant control measure in practice. In addition, disease risk assessment in commonly used plant genotypes is a prominent issue. In this respect, nine commercially grown Greek olive varieties (‘Amfissis’, ‘Atsiholou’, ‘Chalkidikis’, ‘Koroneiki’, ‘Kothreiki’, ‘Koutsourelia’, ‘Mastoidis’, ‘Megaritiki’, and ‘Tragolia’) and one variety of international interest (‘Picual’) were comparatively evaluated for their resistance to V. dahliae. The roots of young plants were immersed in a concentrated conidial suspension in order to perform an artificial inoculation. We evaluated disease reactions in a 140-day assessment period based on external symptoms (disease severity, disease incidence, and mortality) and calculated the relative areas under disease progress curves (relative AUDPC). The process of qPCR was used to evaluate V. dahliae DNA in vascular tissues and plant growth parameters (height and fresh weight). A cumulative stress response was calculated to consider the overall effect of V. dahliae on olive cultivars. The olive varieties resistance to V. dahliae varied significantly, with ‘Koroneiki’, ‘Tragolia’, and ‘Atsiholou’ being the most resistant. Interestingly, most tested varieties showed a significantly low resistance level, suggesting increased risk for the Greek olive industry due to V. dahliae.

Hyperspectral reflectance is becoming an increasingly popular source of information for plants’ physio-chemical status. In this study, net photosynthetic rate (A) and the activity of four antioxida...

Soil salinization is considered as one of the most important risks for agricultural soils. The objective of this experiment was to study the ecophysiological and the biochemical behaviour of two cultivars of Olea europaea L., 'Chemlali' and 'Koroneiki' under two salinity levels (100 and 200 mM NaCl) and the potential alleviation induced by gibberellic acid (GA3) foliar sprays. Salinity treatments significantly decreased photosynthetic assimilation rate and stomatal conductance compared to the control for both cultivars, but ‘Chemlali’ showed a higher resistance to increasing NaCl salinity compared to 'Koroneiki'. Leaf chlorophyll index also reduced gradually with increasing salinity concentration compared to the control. At the end of the experiment, a decrease in growth and dry matter accumulation was observed. Under high salinity stress, a significant decrease in root DW was recorded by 37% and 59% for ‘Chemlali’ and ‘Koroneiki’, respectively. High salinity stress decreased also shoot DW up to 51% for ‘Chemlali’. However, mannitol concentration increased under increasing salinity levels compared to control for ‘Chemlali’ cultivars. Interestingly, foliar application of GA3 alleviated the negative effects of salinity on ecophysiological parameters especially for ‘Koroneiki’. Indeed, GA3 improved photosynthetic assimilation up to 14% for ‘Chemlali’ and 36% for ‘Koroneiki’ compared to high salinity treatment. Both cultivars showed an increase in leaf chlorophyll index after applying GA3. Under high salinity combined with GA3, growth and dry weight were increased compared to salt stressed plants without GA3. The obtained results report that ‘Chemlali’ cultivar is more tolerant to salinity than ‘Koroneiki’ and suggest that GA3 plays an important role to reduce negative effects of NaCl salinity.

commonly known as ‘Esca’, is a detrimental fungus for many tree species and grapevine and is considered to be one of the main causal agents of wood decay of olive plantations in the Mediterranean...

Although Greece is the world’s third largest olive production country, information about the presence of olive viruses is limited. A survey for the presence of virus infections in the ten most important Greek cultivars was conducted in a germplasm collection olive grove located in Chania, Crete. Samples were RT-PCR assayed for the presence of Arabis mosaic virus (ArMV), Cherry leafroll virus (CLRV), Strawberry latent ring spot virus (SLRSV), and Olive leaf yellowing-associated virus (OLYaV), amplifying part of the capsid protein (ArMV), the 3΄UTR (CLSRV, SLRSV) or the HSP70h (OLYaV) gene. Total RNAs were purified using the Trizol method, yielding good quality and purity, thereby confirming application of the method as a rapid economic extraction protocol for detection of olive viruses. SLRSV was the most predominant virus, with an infection rate of 55%, followed by CLRV and OLYaV in 5% of the tested samples. ArMV was detected only in one sample. Mixed virus infections were also commonly detected. The DNA amplicons of the obtained viruses from the infected samples were sequenced. The partial sequences of ArMV, CLRV and SLRSV from olives, which are reported for the first time, showed 74-100% nucleotide similarity with available homologous sequences from other crops, whereas OLYaV isolates showed high sequence variability of 25%. The phylogenetic analysis based on olive-OLYaV HSP70h partial-nucleotide sequences grouped the olive isolate sequences according to the geographical origins of the host germplasm collection. This is the first official report of the occurrence of olive viruses in Greece, emphasizing the need to implement a certification programme for production and distribution of high-quality (virus-free) olive propagation material, in Greece and more generally in the Mediterranean basin.

Salinity and drought stresses are critical for Phaseolus vulgaris L. growth and development. They affect plants in various ways, including tissue mineral element content. Micro- and macro-elements ...

The olive tree (Olea europaeaL.) is one of the main crops of the Mediterranean region which suffers from drought and soil salinization. We assessed the photosynthetic rate, leaf water content and antioxidative enzyme activity (APX, GPX, SOD and CAT) of three Greek olive cultivars (‘Amfisis’, ‘Mastoidis’ and ‘Lefkolia Serron’) subjected to drought and salinity stresses. Hyperspectral reflectance data were acquired using an analytical spectral device (ASD) FieldSpec®3 spectroradiometer, while principal component regression, partial least squares regression and linear discriminant analysis were used to estimate the relationship between spectral and physiological measurements. The photosynthetic rate and water content of stressed plants decreased, while enzyme activity had an increasing tendency. ‘Amfisis’ was more resistant to drought and salinity stress than ‘Mastoidis’ and ‘Lefkolia Serron’. The NDVI appeared to have the highest correlation with the photosynthetic rate, followed by the PRI. APX enzyme activity was the most highly correlated with the 1150–1370 nm range, with an additional peak at 1840 nm. CAT enzyme activity resulted in the highest correlation with the visible part of the spectrum with two peaks at 1480 nm and 1950 nm, while GPX enzyme activity appeared to have a strong correlation within all the available spectral ranges except for 670–1180 nm. Finally, SOD activity showed high correlation values within 1190–1850 nm. This is the first time the correlation of hyperspectral imagery with photosynthetic rate and antioxidant enzyme activities was determined, providing the background for high-throughput plant phenotyping through a drone with a hyperspectral camera. This progress would provide the possibility of early stress detection in large olive groves and assist farmers in decision making and optimizing crop management, health and productivity.

Detailed knowledge of soil properties is fundamentally important for optimizing agriculture practices and management. Meanwhile, the spatial distribution of soil physicochemical properties is considered a fundamental input of any sustainable agricultural planning. In the present study, ordinary kriging, regression kriging and IDW were chosen for deciphering soil spatial variability and mapping soil properties in a reclaimed area of the Behera Governorate of Egypt where soil arose from two different types, one sandstone and the other limestone. Geostatistics were used to show the interrelationships and conditions of soil properties (available phosphorus, potassium and nitrogen, EC, pH, Sp, ESP, CEC, OC, SAR, and CaCO3). The results of mapping spatial soil variability by Geostatistics could be used for precision agriculture applications. Based on the soil test results, nutrient management recommendations should be applied regarding variable rates of fertilizers. The performance of the maps was evaluated using Mean square error (MSE). Inverse distance weight (IDW) showed higher efficiency than Kriging as a prediction method for mapping the studied soil properties in the study area. The results of the present study suggest that the application of the selected fit model worldwide in any relevant study of soil properties of different geological sources is feasible.

Land evaluation is imperative for its efficient use in agriculture. Therefore, this study aimed at assessing the suitability of a region in West El-Minia for cultivating some of the major crops using the geographical information system (GIS). The results focus on allocating space for cultivating sugar beet and utilizing the free period of sugar beet in other crops. This exploitation helps to maintain the quality of the land and increase its fertility by using crop rotation with integrated agricultural management. A machine learning technique was implemented using the random forest algorithm (RF) to predict soil suitability classes for sugar beet using geomorphology, terrain attribute and remote sensing data. Fifteen major crops were evaluated using a suitability multicriteria approach in GIS environment for crop rotation decisions. Soil parameters were determined (soil depth, pH, texture, CaCO3, drainage, ECe, and slope) to characterize the land units for soil suitability. Soils of the area were found to be Entisols, Typic Torrifluvents, Typic Torripsamments and Typic Torriorthents and Aridsols, Typic Haplocacids, Calcic Haplosalids and Sodic Haplocalcids. Overall, the studied area was classified into four suitability classes: high “S1”, moderate “S2”, marginal “S3”, and not suitable “N”. The area of each suitability class changed depending on the crop tested. The highest two crops that occupied S1 class were barley with 471.5 ha (representing 6.8% of the total study area) and alfalfa with 157.4 ha (2.3%). In addition, barley, sugar beet, and sorghum occupied the highest areas in S2 class with 6415.3 ha (92.5%), 6111.3 ha (88.11%) and 6111.3 ha (88.1%), respectively. Regarding the S3 class, three different crops (sesame, green pepper, and maize) were the most highly represented by 6151.8 ha (88.7%), 6126.3 ha (88.3%), and 6116.7 ha (88.2%), respectively. In the end, potato and beans occupied the highest areas in N class with 6916.9 ha (99.7%) and 6853.5 ha (98.8%), respectively. The results revealed that the integration of GIS and soil suitability system consists of an appropriate approach for the evaluation of suitable crop rotations for optimized land use planning and to prevent soil degradation. The study recommends using crop rotation, as it contributes to soil sustainability and the control of plant pests and diseases, where the succession of agricultural crops on a scientific basis aims at maintaining the balance of nutrients and fertilizers in the soil.

Despite the fact that the olive tree is one of the best-adapted species in Mediterranean hydroclimate conditions, climate extremes impose negative effects on olive fruit set and development and subsequently on crop yield. Considering that the frequency of climate extremes is increasing in the last years due to climate change, Good Agricultural Practices (GAPs) have to be applied in order to mitigate their impact on olive trees. In this context, 18 experimental olive groves (irrigated and rainfed) were established, located on the island of Crete (south Greece). A set of 13 GAPs were applied in different combinations, mainly targeting to reduce water losses and erosion, alleviate heat stress and increase water use efficiency. Each experimental orchard was divided into two parts, the control (business-as-usual) and experimental (GAPs implementation). Four indicators were used for the assessment of GAPs performance, namely, Water Productivity (WP), Economic Water Productivity (EWP), Runoff (RF), and Yield (Y). WP and EWP were found to be up to 2.02 and 2.20 times higher, respectively, in the demonstration part of the orchards compared to the control, while Y was found to be up to 119% higher. RF was higher up to 190% in the control compared to the demonstration part of the experimental orchards. The above results clearly demonstrate that the implementation of the proposed GAPs can significantly support the adaptation of olive crops to extreme conditions.

The main aim of the LIFE+ OLIVECLIMA project is to trial the introduction of new cultivation practices for tree crops in order to find a cost-effective means of mitigating and adapting to climate change, through the increase of carbon sequestration by soils, and reduction of greenhouse gases emissions. In order to determine the benefits of using cover crops on soil fertility and biodiversity, an investigation with different combinations of legumes and oat has been conducted during 2014-2015 in Chania, Greece, in a low tree density rain-fed olive orchard covered dominantly by Oxalis pes-caprae weed. The treatments were: natural vegetation, bare soil, only oats, only Vicia sativa, mixture of four legumes with oats and mixture of five legumes with oats. Seed emergence and soil cover was monitored and soil was monthly sampled at three depths (0-10, 10-20 and 20-30 cm) for analysis. During plant growth, significant fluctuations in soil NO(3)-N and NH(4)-N content were recorded. Similarly, soil CO(2) emissions increased with plant growth and air temperature raise. Sowing cover crop mixtures is a promising soil management practice to increase soil fertility and enrich plant and microbial biodiversity in olive orchards especially when dominated by Oxalis pes-caprae a very aggressive weed in many Mediterranean areas.

Water scarcity in the Mediterranean region is becoming a growing concern, threatening the viability of agriculture, which is one of the main economic sectors in many areas. The design of an optimal irrigation management plan, based on state-of-the-art measuring and modeling tools, can effectively contribute towards water saving efforts and potentially address the water scarcity issue in the region. This paper describes the development and application of an integrated decision-making system for the management of water resources of olive and citrus crops in the North of Chania, Crete, Greece. The system integrates different field measurements, for example 2088 soil moisture measurements taken within the study area, and modeling approaches to simulate flow in the unsaturated zone. After the successful calibration and validation of the model, the spatio-temporal representation of soil moisture and pore water pressure were used as guidance for developing optimal irrigation plans, taking into account the water needs of olive and citrus crops, aiming to maximize crop yield, agricultural income, and promote water saving efforts. According to the results, water use can be reduced by up to 36% during the dry season, compared to conventional irrigation practices for citrus trees. Similarly, for olive trees, the reduction in water use can reach up to 41%. The proposed methodology can also be cost-effective in terms of water value, saving about 40% from the typical water cost for irrigation in the study area. The impact of climate change on water resources availability in the area and water conservation efforts were also investigated for the period of (2019-2030). Results show that, comparing the Baseline, RCP 8.5 and RCP 4.5 climatic scenarios, the highest savings on average are observed for emission scenario RCP 4.5 with 53.3% water savings for olive trees and 46.7% for citrus trees.

Vitamin E is a general term used to describe a group of eight lipophilic compounds known as tocochromanols. These vitamin E variants are chemically categorised into two classes formed by α-, β-, γ- and δ- tocopherols and tocotrienols isoforms, respectively. The present study describes the concurrent regulation of genes and metabolites orchestrating vitamin E biosynthesis in olive drupes of five distinctive Greek olive cultivars. A combination of analytical, biochemical and molecular approaches was employed in order to carry out comparative analyses, including real-time RT-qPCR for gene expression levels and HPLC analysis of metabolite content. Findings indicated that tocochromanol levels and composition, oil content, gene expression levels as well as total antioxidant activity were highly dependent on cultivar and, to a lesser extent, on fruit developmental stage. Specifically, cultivars 'Kalokairida' and 'Lianolia Kerkyras' demonstrated the highest vitamin E content. The latter possessed high tocochromanol content combined with highest overall antioxidant activity in all developmental stages, concomitant with the up-regulation expression profile of HPPD. The genotypic imprint versus the temporal contribution to vitamin E levels, as well as the potential link to lipid peroxidation amelioration, are discussed.

International audience; The 'pollen test' and 'fruit set test' following controlled crossing combinations of parents are the most commonly used methods for pollination incompatibility studies in Olea europaea L. Self-incompatibility (SI), with diagnoses based on the pollen test and pollen germination, indicating self-compatibility, is not always followed by fruit set in this species. To solve this dispute, we have reconciled all observations into a new model. Mismatches between field and laboratory data and between methods are resolved by the dual-successive-screen model (DSSM) supposing two different loci for the expression of the two SI mechanisms. Pollen/stigma is controlled by diallelic SI, or DSI, inferring two G1 and G2 compatibility/incompatibility (C/I) groups for varieties, whereas pollen tubes in ovaries are controlled by poly-allelic SI or PASI with twenty C/I groups. To explain the selfing of varieties, we have suggested that some determinants in the pollen tube and stigma are unstable and degrade (DS-D for degradation of S-determinant) after three to five days, enabling some pollen tubes to avoid being rejected, hence reaching ovules. DSI and PASI in the DSSM and DS-D mechanisms, plus the andromonoecy of the olive tree, complexify SI studies. Inferences from DSSM and DS-D mechanisms in olive orchard practice are detailed.

Olive tree growth and reproduction are severely affected by temperature extremes, compromising fruit yield. In that aspect, the olive varieties &ldquo, Koroneiki&rdquo, and &ldquo, Mastoidis&rdquo, were employed in a mild cold stress experiment, imitating night frost incidents to assess their biochemical, physiological and reproductive functions in relation to genotype. The physiological performance of the stressed plants was not significantly altered, suggesting that both cultivars were well adapted to mild cold night stress. The biochemical response of the plants, regarding antioxidant enzymes, H2O2 and TBARS accumulation, confirmed that both cultivars could cope with the stress applied. The mRNA levels of the PPO gene, which participates in hydroxytyrosol biosynthesis and plant defense, were elevated after 24-h stress at 0 &deg, C, in both cultivars with &ldquo, plants exhibiting higher levels for a longer period. Three more genes involved in hydroxytyrosol biosynthesis upregulated their expression levels as a response to cold stress. The numerous plant phenology aspects measured reinforced the conclusion that both cultivars responded to the stress applied. The results of the present study may contribute to better understanding olive tree adaptive responses to low temperature events, an abiotic stress condition that is often present in an open plantation, thus assisting farmers on breeding and cultivar selection.

High relative air humidity (RH ≥ 85%) is frequent in controlled environments, and not uncommon in nature. In this review, we examine the high RH effects on plants with a special focus on stomatal characters. All aspects of stomatal physiology are attenuated by elevated RH during leaf expansion (long-term) in C3 species. These include impaired opening and closing response, as well as weak diel oscillations. Consequently, the high RH-grown plants are not only vulnerable to biotic and abiotic stress, but also undergo a deregulation between CO2 uptake and water loss. Stomatal behavior of a single leaf is determined by the local microclimate during expansion, and may be different than the remaining leaves of the same plant. No effect of high RH is apparent in C4 and CAM species, while the same is expected for species with hydropassive stomatal closure. Formation of bigger stomata with larger pores is a universal response to high RH during leaf expansion, whereas the effect on stomatal density appears to be species- and leaf side-specific. Compelling evidence suggests that ABA mediates the high RH-induced stomatal malfunction, as well as the stomatal size increase. Although high RH stimulates leaf ethylene evolution, it remains elusive whether or not this contributes to stomatal malfunction. Most species lose stomatal function following mid-term (4–7 d) exposure to high RH following leaf expansion. Consequently, the regulatory role of ambient humidity on stomatal functionality is not limited to the period of leaf expansion, but holds throughout the leaf life span.

Olive cultivation is considered as one of the most significant agricultural activities in Greece, from a financial, social, and ecological point of view. Intensive cultivation practices in combination with the Mediterranean climate, lead to depletion of soil organic matter, erosion, desertification, and degradation of water resources. This paper describes sustainable olive crop management practices that were comparatively applied in 120 olive groves in Greece for 5 years with the participation of three farmers groups. Organic materials recycled in the olive groves during the present study were valuable sources of carbon, nitrogen, phosphorus, and potassium. Carbon content was highest in pruning residue (53.8&ndash, 54.2%) while all materials studied were considered rich in C ranging between 41.9&ndash, 46.2% (compost) and 34.9&ndash, 42.5% (three-phase olive mill waste-OMW). The highest content in nitrogen was detected in compost (2&ndash, 2.45%) followed by pruning residue (0.93&ndash, 0.99%) and OMW (0.03&ndash, 0.1%). Compost was considered a good source of phosphorus (0.3&ndash, 0.6%) followed by pruning residue (0.08&ndash, 0.13%) and OMW (0.01&ndash, 0.3%). Potassium was also considerable in the organic materials recycled ranging 0.5&ndash, 1.5% in compost followed by pruning residue (0.5&ndash, 0.7%) and OMW (0.3&ndash, 1.1%). Adoption of modified pruning also had important contribution toward sustainable management of olive trees. Sustainable pruning resulted in a well-balanced ratio between vegetative growth and fruiting (balanced, every year, in order to eradicate biennial bearing). Significant fluctuation in olive yields was observed in the first years of the project while yields were gradually stabilised by applying sustainable crop management. In parallel, yield increase without additional inputs, lowers the carbon&mdash, environmental footprint of the product regarding several environmental impact categories. Results can be integrated in the national agricultural and environmental policy in Mediterranean countries toward the achievement of a circular economy.

Wood decay caused primarily by Fomitiporia mediterranea is considered to be an emerging disease for citrus and olive trees in Mediterranean countries. The pathogen cannot be currently controlled by chemicals whereas there is no available information about the source and level of resistance even for the most important cultivars where the global citrus and olive industries are based on. In the present study, five of the most significant Greek olive cultivars (Amfissis, Chalkidikis, Kalamon, Koroneiki and Mastoidis) were evaluated for their resistance to F. mediterranea by conducting artificial inoculation experiments. Disease reactions were evaluated by measuring the length of bark and wood lesions, 33 months post inoculation. Trunk sections scanning and image pixel analysis were employed to estimate the total discoloration and decay area of infected wood, whereas positive re-isolation ratio of F. mediterranea was also taken into account in resistance evaluation. Data on symptom development along with wood tissue colonization by the pathogen indicated that the resistance of olive cultivars to F. mediterranea varied significantly. Based on the cumulative stress response index (CSRI), ‘Kalamon’ and ‘Koroneiki’ were classified as resistant, ‘Chalkidikis’ and ‘Mastoidis’ as intermediately resistant, whereas ‘Amfissis’ was susceptible. Determination of lignin in trunk wood showed that the resistance of olive cultivars to F. mediterranea could be associated with their lignin content. This is the first experimental evidence of differential susceptibility responses of olive cultivars against F. mediterranea, and reveals for the first time the potential exploitation of host resistance as a promising approach in the effort to control wood decay disease of olive in practice.

Olive trees constitute one of the most dynamic cultivations for Mediterranean countries, while their economic importance is high. As water constitutes a fundamental factor affecting olive tree production, soil water content is a most critical parameter that must be monitored to improve olive trees’ cultivation management. Effects of precipitation, irrigation, and soil management on water content in four soil depths (10, 20, 30, 40 cm), four periods of the year (February–March, April–May, June–July, August–September) and three successive years were determined in 12 Mediterranean olive groves (Trifilia, southern Greece) as well as their respective fruit and olive oil yields. Significantly higher soil water content was recorded in the first (+16.8%) and third (+27.4%) year compared to the second year. Higher (+6.8%) water content was observed in irrigated olive groves compared to rainfed fields. Higher (+5.6%) water content was observed in sustainable olive groves compared to intensively managed fields. Significantly, higher soil moisture was recorded at 40 and 30 cm depth compared to 10 cm depth while intermediate values were observed at 20 cm. Marked increase in fruit yield was achieved through sustainable management (+39%) compared to intensive olive groves. The potential to improve irrigation practices in the area was also indicated by results of the present study.

The objective of this work was to classify and map the areas environmentally sensitive to desertification in the Mediterranean island of Crete. Sensitivity to desertification was estimated with a modification of the MEDALUS Environmentally Sensitive Area Index (ESAI) approach, using 15 quantitative parameters divided into four main quality indices: climate, vegetation, soils and management quality. The ESAI methodology was modified to include two additional parameters related to soil quality (water erosion and soil organic matter). According to the results, 37% of the island's area is characterized as critically sensitive to desertification. This percentage varies significantly across the island, with the western part having the least critically sensitive areas, and the eastern part the most critically sensitive. The results of this study also indicate that critically sensitive areas are found in the eastern side of the island mainly due to human-related factors and climatic conditions. It was concluded that the proposed methodology is a valuable tool for regional-scale assessment of areas environmentally sensitive to desertification in Mediterranean environments.

Olive trees are a major source of agricultural residues. Strategies based on different management of organic amendments have been reported to increase soil fertility. The effect of sustainable organic matter input practices (application of shredded pruning residue and olive residue compost to soil) on soil properties in irrigated and rain-fed olive groves was investigated. The study took place in 40 olive groves in the region of Peza, island of Crete, Greece during a 5-year period (2012–2017). The results showed that olive trees play an important role in soil nutrient conservation under semi-arid conditions in the Mediterranean basin. The addition of olive tree residues, in combination with conservation tillage practices, improved soil fertility over the experimental period. Most of the soil properties were favored by irrigation. In olive soil parcels receiving organic materials the soil organic matter and the total nitrogen were increased in irrigated fields. The ability of surface soil to sequester carbon and nutrients beneath the tree canopy of olive groves was high. It is recommended that sustainable soil management practices should consider soil fertility variability of olive orchards.

The effect of addition of organic materials (shredded pruning residues, composted olive mill by-products) on spatial distribution of soil chemical and microbial properties in irrigated and rainfed olive groves was investigated. Most of the soil parcels were subjected to reduced tillage or no tillage practices. Soil sampling took place in 40 olive groves in the region of Messinia, south-western Peloponnese, Greece during a 5-year period (2012–2017). The results showed significant increases in soil organic matter, humic acids and nitrate content at the end of the study period, compared to the first year of the soil sampling campaign. On the other hand, the relatively low amount of fresh organic materials that was applied to the soil produced unfavorable results. Differences between irrigated and rainfed soil parcels were not significant, for most of the soil properties, since the area receives much higher loads of rain than the average rainfall, as registered in the main olive growing regions of Greece. The area underneath the tree canopy favors an environment that enhances soil fertility, compared to the area out of the tree canopy. Changes of soil properties according to depth showed that the surface soil in olive orchards has the potential to sequester carbon and nutrients.

The aim of the present study was to determine the short-term effects (three years) of four sustainable management systems including different carbon inputs (compost, pruning residues and cover crops, applied solely or combined) on the mineral content of soil, olive trees and weeds, on some specific groups of soil microorganisms, and on weed mycorrhizal colonization in an olive orchard compared to a conventional system involving soil tillage and only mineral forms of fertilizers. The study was performed between 2013 and 2015 in a 40-year-old olive plantation. The results showed that soil organic matter, as well as main macro- and micronutrients, were markedly improved following three years of increased biomass inputs. Data related to the mycorrhizal colonization of spontaneous weed flora and to actinobacteria, Azotobacter and proteolytic bacteria suggest favourable effects on soil biology and agro-ecosystem complexity. Sowing a mixture of winter cover crops for three successive years also contributed to soil enrichment in biological as well as mineral nutrient aspects. Adoption of the sustainable management here applied practices is in complete agreement with the European policy on the transition from a linear to a circular economy and would provide significant benefits for rural stakeholders and ecosystems in the long term.

Some imperative developed genotypes of almond (‘Tardy Nonpareil’, ‘Nonpareil’, ‘Sahand’, ‘Rabie’, ‘Azar’, ‘Shekofeh’, ‘Sefied’ and ‘Mamaei’) were utilized in two experiments for 3 years to elucidate the genotype response of almond pollen germination and tube development at various temperature levels. Pollen was subjected to pre-incubation at 10, 20, 30 or 40∘C for 24 h to reproduce temperature stress during pollen dispersal; and then in vitro cultured. In the second examination, pollen was exposed at 15, 20, 25 or 30 °C for 24 h in vitro to assess pollen reaction in state of water and supplements accessibility and to determine the ideal pollen germination and tube development temperatures for every genotype. The most elevated pre- incubation temperature treatment (40 °C) completely prevented pollen germination in “Mamaei” and ‘Sefied’, while even in the less influenced cultivars ('Shekofeh’, ‘Azar’, ‘Rabie’, ‘Sahand’, ‘Tardy Nonpareil’ and ‘Nonpareil’) germination rates were as low as 2–3%. Pre-incubation at 30 ∘C or 40 °C negatively affected pollen germination and pollen tube length. In the second experiment, in vitro pollen germination increased after incubation at 25 °C for ‘Mamaei’ (+2%), ‘Sefied’ (+3%), ‘Shekofeh’ (+3%), ‘Azar’ (+3%), ‘Rabie’ (+4%), ‘Sahand’ (+5%), ‘Nonpareil’ (+5%) and ‘Tardy Nonpareil’ (+5%) compared to the control (20∘C). At 30 ∘C, germination percent for ‘Mamaei’, ‘Sefied’, ‘Shekofeh’, ‘Azar’, ‘Rabie’, ‘Sahand’, ‘Nonpareil’ and ‘Tardy Nonpareil’ was 35, 35, 10, 15, 25, 15, 35, and 20% lower, respectively, compared to the control (20 ∘C). Pollen tube length additionally increased with incubation temperature for all of the considered genotypes. In view of the cumulative stress response index (CSRI) that was calculated for high temperature stress the developed genotypes were arranged: ‘Shekofeh’ and ‘Tardy Nonpareil’ as tolerant and ‘Nonpareil’, ‘Rabie’ and ‘Sahand’ as intermediate at 40 ∘C, while ‘Azar’, ‘Rabie’, Sahand’ and ‘Tardy Nonpareil’ as tolerant, ‘Shekofeh’ and ‘Nonpareil’ as intermediate and ‘Mamaei’ and ‘Sefied’ as sensitive at 30 °C. The observed strong genotype differentiated reaction in high and low temperature stress could be utilized by plant breeders towards producing new tolerant almond genotypes.

The olive tree of Vouves in Crete, is considered the oldest producing olive tree in the world with an estimated age exceeding 4000 years. In the present study, we sequenced two samples (from the bottom and the top of the tree) to elucidate the genetic relation of this ancient tree with other olive cvs as well as to gain some insights about its origin. Our results showed that both samples have different genetic origins, proving that this ancient tree has been grafted at least one time. On the basis of whole genome sequences the sample from the top of the Vouves tree showed relation of the same order than half-siblings to one accession corresponding to the present-day Greek cv ‘Mastoidis’. Nevertheless, in the framework of a microsatellite analysis it was found to cluster with the ‘Mastoidis’ samples. The Vouves rootstock (bottom sample) showed a clear grouping with the oleaster samples in a similar way to that of ‘Megaritiki’ Greek cv although it does not show any signal of introgression from them. The genomic analyses did not show a strong relation of this sample with the present-day Greek cvs analyzed in this study so it cannot be proved that it has been used as a source for cultivated olive tree populations represented by available genome sequences. Nevertheless, on the basis of microsatellite analyses, the Vouves rootstock showed affinity with two present-day Greek cvs, one “ancient” rootstock from continental Greece as well as monumental trees from Cyprus. The analysis of the impact of the variants in the gene space revealed an enrichment of genes associated to pathways related with carbohydrate and amino acid metabolism. This is in agreement with what has been found before in the sweep regions related with the process of domestication. The absence of oleaster gene flow, its old age and its variant profile, similar to other cultivated populations, makes it an excellent reference point for domestication studies.