Olive Tree Cultivation Research Articles

Genome-wide association analysis of flowering date in a collection of cultivated olive tree

Abstract Flowering date in perennial fruit trees is an important trait for fruit production. Depending on the winter and spring temperatures, flowering of olive may be advanced, delayed, or even suppressed. Deciphering the genetic control of flowering date is thus key to help selecting cultivars better adapted to the current climate context. Here, we investigated the genetic determinism of full flowering date stage in cultivated olive based on capture sequencing data of 318 genotypes from the worldwide olive germplasm bank of Marrakech, Morocco. The genetic structure of this collection was organized in three clusters that were broadly attributed to eastern, central, and western Mediterranean regions, based on the presumed origin of genotypes. Flowering dates, collected over seven years, were used to estimate the genotypic best linear unbiased predictors, which were then analyzed in a genome-wide association study. Loci with small effects were significantly associated with the studied trait, by either a single- or a multi-locus approach. The three most robust loci were located on chromosomes 01 and 04, and on a scaffold, and explained 7.1%, 6.2%, and 6.5% of the trait variance, respectively. A significantly higher accuracy in the best linear unbiased predictors of flowering date prediction was reported with Ridge- compared to LASSO-based genomic prediction model. Along with genomic association results, this suggests a complex polygenic determinism of flowering date, as seen in many other fruit perennials. These results and the screening of associated regions for candidate genes open perspectives for further studies and breeding programs targeting flowering date.

Challenges of Salinity Intrusion and Drought Stress on Olive Tree Cultivation on Mljet Island.

Understanding genotype-specific responses to environmental stressors is vital for developing resilience strategies that ensure sustainable olive cultivation and productivity. In this work, cultivar 'Oblica' and several olive genotypes from the island of Mljet (Croatia) were exposed to short-term (21 days) salinity and drought treatments. In contrast to other olive genotypes, genotype M29 as well as cultivar 'Oblica' managed to maintain growth and chlorophyll a levels under salinity stress to the same level as the control. Drought, however, significantly reduced the growth parameters in all olive trees. Cultivar 'Oblica' accumulated the greatest amount of Na+ ions in the leaves compared to olive genotypes from the island of Mljet, demonstrating superior resistance by translocating Na+ to leaf vacuoles. The observed reduction in K+ content in the roots of olive trees under all treatments suggests a generalized stress response. On the other hand, effective Ca2+ uptake has been identified as a crucial energy-saving strategy that olive trees use to cope with brief periods of salinity and drought. The proline content and activities of superoxide dismutase (SOD) and guaiacol peroxidase (GPOX) varied among the olive trees, highlighting the importance of antioxidative capacities and stress adaptation mechanisms. According to the obtained results, stress-resistant olive genotypes like 'Oblica' and M29 show potential for breeding resilient varieties.

Effect of Waterlogging on Growth and Productivity of Fruit Crops

Τhe production of fresh fruit as well as olive orchards is increasing around the world, in order to meet the global demand for both fruits and olive products. This results in the spread and establishment of fruit and olive tree cultivation in areas where they were not found before, for example, plains and lowlands prone to waterlogging. Climate change is having a significant impact on the natural environment. Agricultural open-field crops have less growth and yield under these harsh weather conditions. Nowadays, unpredictable rainfall more often exposes field crops to waterlogging on a regular basis. This is a very stressful factor which can cause a reduction in yield and even total crop elimination. In this review, the morphological and physiological parameters affected by waterlogging are developed in order to understand better how olive and other fruit crops respond to waterlogging conditions and how this affects their development and productivity. Having a better understanding of these mechanisms can help us design strategies and approaches to increase fruit crop resistance to waterlogging stress.

Spatial analysis of olive fly on Samos island

Cultivation of olive-trees is one of the landmark land-uses and agroecosystems of the Mediterranean. The single most important factor of production-loss is infestation by the olive fruit fly (OLF, Bactrocera oleae). We examine the spatiotemporal dynamics of OLF populations on Samos Island by employing spatial-analysis methods for a focused estimation on olive plantations. The case study includes a variation of areas across altitude. We use data for three years (2017–2019) from 399 trap locations that are not associated with farms or other major anthropogenic installations and measure temperature and humidity in 24 locations across the island to: examine the temporal variation of OLF populations, to check the relationship of temperature, humidity, and geomorphological characteristics and calculate the estimated spatial distribution of OLF. Results show small differences of annual averages, but very important spatiotemporal differences and micro hot/cold spots of OLF populations. Findings suggest significant movement of OLF populations across landscape. This approach can help achieve a deeper understanding of OLF behavior in Mediterranean ecosystems and contribute toward new approaches in pest management of olive trees.

Deep Learning-based Lightweight Models for Bactrocera Oleae Detection

The detection of Bactrocera oleae (BO), an invasive pest that poses a serious threat to olive tree cultivation, is crucial for ensuring the quality and quantity of olive oil production. This study explores the application of deep learning with lightweight models for BO detection in olive trees. The DIRT Dataset, consisting of 841 images obtained from traps, was used for training and evaluation. Different combinations of Faster R-CNN and SSD models with various backbone architectures, including EfficientNet B0, MobileNet v3, ResNet-18, and ResNet-50, were assessed. The combination of Faster R-CNN with ResNet-18 achieves comparable results to Faster R-CNN with ResNet-50 but with lower latency and a reduced parameter count. These findings highlight the potential of deep learning-based object detection models for BO detection in olive trees, offering efficient and accurate identification of infestations.

Oliviculture and Viticulture Crop Byproducts Use for Peat Partial Substitution for Carnation Production

The intensive cultivation of olive trees and grapevines in the Mediterranean region not only results in large yields but also generate wastes, with high restrictions on their impact on people’s well-being and the environment. The current study sought to investigate the potential use of olive-mill waste (OW), grape-mill waste (GW) and their mixtures (OW + GW) at different levels (0%, 5%, 10% and 20% v/v) for partial peat substitution in the production of carnation (Dianthus caryophyllus L.) plants. The presence of OW, GW and OW + GW wastes raised the pH, the electrical conductivity, the content of organic matter and mineral content in substrate mixtures, while they decreased the total porosity and the available free air. The use of OW had more negative impacts than GW, while the OW + GW mixture alleviated, to some extent, the negative OW impacts. The use of high levels of residues decreased plant growth, chlorophyll content and mineral accumulation in plant tissue due to inappropriate growing media properties. The increased OW presence caused oxidative stress to the plants, as verified by the increased malondialdehyde and hydrogen peroxide content. This resulted in an upsurge in the total phenolics. However, GW presence did not impact any oxidative stress. It can be suggested that 10% OW, 10% GW or 20% OW + GW can be used in growing media, as they resulted in suitable plant growth. To ensure sufficient yields, nevertheless, the growing media’s characteristics also need to be enhanced.

OLEAtool: An open-source software for morphopalynological research in Olea europaea L. pollen

In this paper we present OLEAtool, a new software tool for palynological research to facilitate morphological analysis and measurements of Olea pollen. OLEAtool is a macro extension for use with ImageJ, an open-access and freely available image analysis software, and was developed as a component of the OLEA-project. This larger project examines olive tree expansion and mosaic landscape formation on the Balearic Islands. Pollen analysis of both fossil and modern grains has been proven useful for characterizing cultivars and therefore an important method for studying olive tree cultivation in the Mediterranean. However, these methods still struggle with distinguishing between wild and cultivated varieties. Traditional morphological analysis of pollen grains can be a difficult and time-consuming task. However, OLEAtool dramatically increases the speed of collecting data on pollen grains, expands the number of variables an analyst can measure, and greatly enhances the replicability of morphological analysis.

Simulated drift of 2,4-D and dicamba in pecan (<i>Carya illinoinensis</i> K. Koch) and olive trees (<i>Olea europaea</i> L.)

The cultivation of pecan (Carya illinoinensis K. Koch) and olive trees (Olea europaea L.) near pasture and grain cultivation areas in southern Brazil has caused herbicide drift problems. Therefore, the objective of this study was to evaluate the phytotoxic effects of herbicides 2,4-D and dicamba on the growth of pecan and olive tree seedlings. A total of 8 underdoses were used, as follows: 0, 1.56, 3.125, 6.25, 12.0, 25.0, 50.0, and 100% of the recommended doses of herbicides 2,4-D (670 g a.e ha−1) and dicamba (720 g a.e ha−1) for burndown. The applications were carried out in 80 cm-high seedlings with the aid of a CO2 pressurized sprayer with a spray solution volume of 150 L. ha−1. The analyzed variables were phytotoxicity at 7, 14, 21, 30 and 60 days after spray (DAA) and plant height and stem diameter at 30 and 60 DAA. The drift of hormonal herbicides caused damage to the growth of pecan and olive trees, decreasing their stem diameter and height, with the herbicide dicamba showing the greatest damage. In addition, doses above 12.5% of both herbicides resulted in phytotoxicity levels greater than 60%, and doses of 50 and 100% were responsible for leaf senescence.

Genomic evidence of genuine wild versus admixed olive populations evolving in the same natural environments in western Mediterranean Basin.

Crop-to-wild gene flow is a mechanism process widely documented, both in plants and animals. This can have positive or negative impacts on the evolution of admixed populations in natural environments, yet the phenomenon is still misunderstood in long-lived woody species, contrary to short-lived crops. Wild olive Olea europaea L. occurs in the same eco-geographical range as domesticated olive, i.e. the Mediterranean Basin (MB). Moreover, it is an allogamous and anemophilous species whose seeds are disseminated by birds, i.e. factors that drive gene flow between crops and their wild relatives. Here we investigated the genetic structure of western MB wild olive populations in natural environments assuming a homogenous gene pool with limited impact of cultivated alleles, as previously suggested. We used a target sequencing method based on annotated genes from the Farga reference genome to analyze 27 western MB olive tree populations sampled in natural environments in France, Spain and Morocco. We also target sequenced cultivated olive tree accessions from the Worldwide Olive Germplasm Bank of Marrakech and Porquerolles and from an eastern MB wild olive tree population. We combined PCA, sNMF, pairwise FST and TreeMix and clearly identified genuine wild olive trees throughout their natural distribution range along a north-south gradient including, for the first time, in southern France. However, contrary to our assumption, we highlighted more admixed than genuine wild olive trees. Our results raise questions regarding the admixed population evolution pattern in this environment, which might be facilitated by crop-to-wild gene flow.

Climate Suitability for the Cultivation of Olive Trees in Iraq

Objectives: This research aims to assess the suitability and availability of climatic conditions for olive cultivation in Iraq. The study identifies the most and least suitable areas, along with intermediate areas, utilizing the ArcMap program for mapping and delineating agriculturally favorable regions.
 Methods: A descriptive approach was employed in this research, as an analytical approach was deemed essential for describing and analyzing data to attain scientific accuracy.
 Results: The research findings indicate that certain areas, namely Mosul, Erbil, Sulaymaniyah, and Kirkuk, exhibit high suitability for olive tree cultivation. The station at Al-Rutba demonstrates moderate feasibility, while Basra, Nasiriyah, Amarah, Baghdad, Diwaniyah, and Al-Hay are deemed unsuitable due to the absence of necessary climatic conditions for olive cultivation.
 Conclusions: The study concludes that climatic factors vary in their impact on olive cultivation and production. Temperature emerges as a significant contributor, while other factors such as humidity and wind play a limited role. Light is identified as a crucial factor affecting fruit size, composition, and color.

Wild and cultivated olive tree genetic diversity in Greece: a diverse resource in danger of erosion.

The genetic relationships between Greek wild olive tree populations and cultivars were investigated. A total of 219 wild genotypes and 67 cultivar genotypes were analyzed by employing 10 SSR markers. Data evidenced that the wild populations exhibited high levels of genetic diversity and exclusively host 40% of the total number of alleles detected. Inbreeding was observed within populations, probably as a consequence of their fragmented spatial distribution. The genetic differentiation between cultivars and wild individuals, as well as within wild populations, was low. Nevertheless, three gene pools of wild trees were detected, corresponding to the geographical areas of Northeastern Greece, Peloponnese-Crete and Epirus. Most cultivars clustered in a separate group, while the rest of them formed a heterogenous group with membership coefficients akin to the three wild olive clusters. Regarding the history of olive cultivation in Greece, bidirectional gene flow was detected between populations of Peloponnese-Crete and the gene pool that composes some of Greece's most important cultivars, such as "Koroneiki" and "Mastoidis", which is inferred as an indication of a minor domestication event in the area. A strategy for the protection of Greek-oriented olive genetic resources is proposed, along with suggestions for the utilization of the genetically diverse wild resources with regard to the introgression of traits of agronomical interest to cultivars.

Traditional Olive Tree Varieties in Alto Aragón (NE Spain): Molecular Characterization, Single-Varietal Oils, and Monumental Trees

Recovering minority olive tree varieties helps preserve genetic diversity and contributes to sustainable agriculture practices. The International Olive Council has recognized the importance of conserving olive tree genetic resources and the European Union’s Horizon Europe program has identified the preservation of crop diversity as a priority for sustainable food systems. In the work presented herein, old olive groves in the province of Huesca (NE Spain), managed according to the traditional model, were surveyed, sampled, and analyzed using molecular characterization techniques (based on EST-SNPs markers). Twenty-nine new varieties were identified and deposited in IFAPA’s World Germplasm Bank of Olive Varieties. In the first step towards their valorization, eight single-varietal oils from Alto Aragon varieties were produced and characterized, and their organoleptic properties were evaluated, paving the way for the production of differentiated quality oils. Furthermore, ancient olive trees were selected and 3D scanned to promote their protection as singular or monumental trees and for oleo-tourism purposes. The reported findings highlight the rich olive-growing heritage of this northernmost frontier of olive tree cultivation in Spain.

Soil erosion rates evaluation via 137Cs and RUSLE modeling in the Sigilil watershed (northeastern Tunisia)

Soil erosion is a natural phenomenon which causes many problems such as the reduction of soil fertility and silting of dams. In this study, the 137Cs activities and the RUSLE model were used to quantify soil erosion rates in the Sgilil river watershed of northeastern Tunisia, and where 20% of the agricultural land is devoted to the cultivation of olive trees. In addition, the erosion dynamics and its spatial variation were inferred. The net erosion rates in the cultivated field based on the measured 137Cs activities and using the Fallout Radionuclide Conversion Models range from 2.24 to 34.23 t ha−1 yr−1 when the Proportional Model is applied and from 1.49 to 30 t ha−1 yr−1 when the Mass Balance Model 2 is applied. The average erosion rates of the Sgilil river watershed estimated by the RUSLE model after multiplying five erosion factors for an average year (1990–2019) is 6 t ha−1 yr−1. Based on the RUSLE model results, around 52% of the watershed area falls within the slight erosion risk class (0–2 t ha−1 yr−1) and 11% within the very severe erosion risk class (> 30 t ha−1 yr−1). The center of the watershed, where the olive cultivated field is located belongs to a high to severe erosion risk class. Results attained through the isotopic approach and those found through the RUSLE modeling are in agreement.

Assessment of roadside pollution by heavy metals: A case study from the District of Bani Kinanah, Irbid, Northern Jordan.

The District of Bani Kenanah is home to natural reserves, forests, local agricultural practices, and a multitude of historical and cultural sites. The majority of the population in the study area is employed in the agricultural sector, which is dominated by olive tree cultivation and the production of premium olive oil. The current study aimed to assess the degree of roadside soil pollution and predict the potential ecological impacts of Pb, Cd, Zn, Cr, Ni, Mn, Cu, Fe, and Co. Therefore, 30 soil samples were collected and analyzed with a Flame atomic absorption spectrophotometer for the aforementioned metals. The spatial distribution maps of these metals were generated by inverse distance weighted (IDW) interpolation in ArcGIS 10.3. The values of heavy metals (HMs) in the study were lower than the international standards for soil quality. The soil was classified as moderately to substantially enriched with Cd, Pb, and Zn based on the EF values. However, the indices of geo-accumulation (Igeo), contamination factor (CF), and potential ecological risk (RI) generally revealed minor metallic contamination. The traffic and agricultural activities were the potential sources of Cd, Pb, and Zn in the study area. Incorporating HMs analysis with GIS maps was beneficial for assessing soil pollution.

White rice enrichment with phenols upon cooking in olive leaf infusion: a preliminary study.

White rice is poor in health-promoting phytochemicals; therefore, the production of a phenol-enriched commodity is highly desirable. Recent findings on its enrichment via cooking in plant extracts are promising, yet studies employing aqueous extracts of olive leaves (OLs), containing well-recognized bioactive phenols (e.g. oleuropein) are absent. In addition, little is known about the levels of phenols that are maintained after rice drying and rehydration, an important aspect for the future design of 'ready-to-eat' functional rice. The examination, for the first time, of white rice adsorption capacity of phenols from OLs upon cooking in infusions containing different levels of phenols, after freeze-drying and rehydration, showed the following: (i) the total phenol content, the antioxidant activity (assessed via 2,2-diphenyl-1-picrylhydrazyl radical and ferric reducing antioxidant power assays), the oleuropein and luteolin-7-O-glucoside levels increased dose dependently; (ii) upon rehydration, the average decrease of total phenol content and antioxidant activity values was significantly lower when an exact volume of water was used compared with an excess (~10% versus 63%). A similar trend was observed for oleuropein (36% versus 83%) and the luteolin-7-O-glucoside (24 versus 82%) levels; (iii) the dried enriched kernels were less bright with a hay-yellow hue (CIELab coordinates). White rice enrichment with biophenols from OLs, a by-product of olive tree cultivation, was successful using a simple approach. Despite leaching upon freeze-drying/rehydration, sufficient amounts were maintained to obtain a functional rice that could serve as an alternative dietary source of OLs phenols to non-traditional olive tree product consumers or those refraining from sodium and fats. © 2023 Society of Chemical Industry.

Inquiring Quality Assurance of the Table Olive Products

Table olives are the healthy fruit of the varieties of cultivated olive trees (Olea europaea), selected for the production of olives whose characteristics make them particularly suitable for processing. The processing of the olive is necessary, aiming mainly at the degradation of the phenolic glycoside oleuropein, a compound that gives a bitter taste to the fruit, making it impossible to consume immediately. Also, the various treatments aim to ensure the preservation of the product through the action of lactic acid bacteria (reducing the pH), to improve the quality of the final product (affecting the aroma, taste, texture, etc.). Olive varieties around the world are estimated to reach six hundred. Yet, there are three types of table olives in the market: natural black olives of the Greek type, black olives of California and green olives of the Spanish type. Table olive can be processed according to the method for natural black olives. Natural black olive is a natural product, i.e., the addition of chemicals is minimal. Its processing through the traditional method is simple and requires low energy consumption. The table olive processing plant must implement a healthy food production assurance system to protect the consumers from chemical hazards. This system is the HACCP (Hazard Analysis Critical Control Points) system, which is described by Codex Alimentarius. HACCP and ISO certification are a necessary step for most modern businesses, recognizing that a food business has developed, documented and implemented the right food production, standardization and packaging systems, according to these certifications.

A shift in the paradigm? A male-specific lactone increases the response of both sexes of the olive fruit fly Bactrocera oleae to the food lure ammonium bicarbonate

The olive fruit fly Bactrocera oleae (Rossi) (Diptera: Tephritidae) is a key pest species of wild and cultivated olive trees worldwide. Contrarily to most tephritid flies, in which males release the sex pheromone, in B. oleae the female is the sex responsible of attracting the opposite sex. However, and even though vast research has been done during the last decades, we are still far from understanding the chemical signals involved in the sexual communication of this species, including those produced by males. Here, we report for the first time the presence of two male-specific volatile compounds, namely γ-hexalactone and δ-hexalactone, with the former exerting a significant attraction upon both sexes under laboratory and field conditions. Volatile collections conducted on laboratory-reared virgin individuals of both sexes revealed the presence of these two compounds only in males, regardless of their age. In double-choice behavioral assays, γ-hexalactone resulted to be attractive for virgin males and females (7–14 days old), with no attractiveness reported for δ-hexalactone. Finally, in field assays traps baited with the binary blend of ammonium bicarbonate and γ-hexalactone yielded significantly more catches per week of both sexes than those baited with ammonium bicarbonate and ammonium bicarbonate plus 1,7-dioxaspiro[5.5]undecane, the major sex pheromone component. Altogether, our results shed light on the chemical ecology of the species and represent a promising experimental basis for the development of more innovative and effective mass trapping tools based on the use of γ-hexalactone.

Use of GIS in Selecting Suitable Tree Crop Cultivation Sites in Mountainous Less Favoured Areas: An Example from Greece

The aim of this paper is the selection of suitable tree crop cultivation sites in mountainous less favoured areas, as a forest policy measure under the scope of sustainable development. Ten different crop types were proposed as being most suitable in the study area, Pierion Municipal Unit, which is located in the Municipality of Katerini, in the Pieria Prefecture of Greece. In order to determine the most suitable sites for cultivation, data layers that involved the factors of topography, climate, pedology and geology were derived from existing maps and free-of-charge datasets, so that they could be consequently processed with the aid of Geographic Information Systems (GIS). The data processing was performed by following criteria, which were established in accordance with the current literature and were translated into Boolean algebra expressions. The latter helped to identify locations where the values of the factors that were employed were most favourable for the cultivation of walnut trees (Juglans sp.), olive trees (Olea sp.), cherry trees (Prunus sp.), apple (Malus sp.), dogwood trees (Cornus sp.), pomegranate trees (Punica sp.), chestnut trees (Castanea sp.) and other crop types. Moreover, the resulting map indicated that the majority of the suitable sites for cultivation were considered favourable for growing walnut trees (24.9%), followed by cherry trees (19.6%) and olive trees (12.1%). Proposing the most suitable cultivations within the study area contributes to forest policy planning and promotes the sustainable development of mountainous less favoured areas, leading to a more rational management of natural resources, a raised awareness of environmental protection, the maintenance of the local population and income enhancement through the production of high quality crops and sustainable yields.

Temperature trends of the olive tree cultivation period in the producing areas of Spain (1981-2019)

Temperature trends of the olive tree cultivation period in the producing areas of Spain (1981-2019)

Influence of Experimental Warming on the Rate and Duration of Fruit Growth and Oil Accumulation in Young Olive Trees (cvs. Arbequina, Coratina).

Olive tree cultivation in new warmer areas and climate change have increased the global interest in understanding how air temperature affects both fruit growth and oil accumulation. The aims of this study were to evaluate the rate and duration of fruit growth and oil accumulation in response to experimental warming (+3) in a semiarid region of Argentina; and assess how warming affected fatty acid composition. Young, potted olive trees (cvs. Arbequina, Coratina) were warmed (T+) or maintained near ambient temperature (T0) inside open top chambers in the field during oil accumulation in 2014-2015 or 2015-2016 using different trees in each season. Warming reduced the rate of both fruit growth and oil accumulation in T+ compared to T0 in both cultivars. These rate reductions under T+ led to large decreases in final fruit dry weight and oil concentration. In contrast, the durations (i.e., days) of fruit growth and oil accumulation were most often not affected. Cultivar x temperature interactions were observed in 2014-2015 with warming decreasing oleic acid and increasing linoleic acid in cv. Arbequina, while cv. Coratina showed no response to warming. However, no interactions were found in 2015-2016. Studying how fruit growth and oil accumulation respond to adaptation strategies against increasing air temperatures should be a priority in both young and mature olive trees of numerous cultivars given crop expansion to new regions and future climate scenarios.