Olive (Olea europaea) is one of the most important crop trees, with olive oil being a key ingredient of the Mediterranean diet. Oleuropein, an oleoside-type secoiridoid, is the major determinant of olive oil flavor and quality. Iridoid biosynthesis has been elucidated in Catharanthus roseus, which produces secologanin-type secoiridoids, but iridoid biosynthesis in other species remains unresolved. In this work, we sequenced RNA from the fruit mesocarp of six commercial olive cultivars with various oleuropein contents during maturation and ripening. Using these data, we discovered three polyphenol oxidases with oleuropein synthase (OS) activity, a novel oleoside-11-methyl ester glucosyltransferase (OMEGT) that synthesizes a potential intermediate in the pathway, and a 7-epi-loganic acid O-methyltransferase (7eLAMT). Interestingly, the use of transcriptome assemblies for 15 plant species from three iridoid-producing plant orders (Lamiales, Gentianales, and Cornales) for orthogroup inference, and integration of two tissue expression panels from Jasminum sambac and Fraxinus excelsior, enabled the discovery of two 2-oxoglutarate-dependent dioxygenases (named 7eLAS) that synthesize 7-epi-loganic acid; by contrast, C. roseus 7-deoxy-loganic acid hydroxylase (7DLH), a known bottleneck in MIA production, is a cytochrome P450. This comparative co-expression method, which combines guilt-by-association and comparative transcriptomics approaches, can successfully leverage large datasets for untargeted discovery of enzymes. Given the increasing availability of expression data from species across the plant kingdom, the methods for gene discovery used in the present work can be readily applied to other untraced pathways.

The olive tree (Olea europaea L.) is a key source of verbascoside, a potent phenylethanoid glycoside known for its antioxidant, anti-inflammatory, and neuroprotective properties. Traditional breeding for enhanced phenolic profiles is limited by the olive's long juvenile period and complex genetics. This study dissected the unknown genetic architecture of verbascoside biosynthesis using a multi-omics strategy integrating metabolomics, Quantitative Trait Loci mapping, and transcriptomics across an F1 population and diverse cultivars. This approach identified a major genetic locus controlling verbascoside content on chromosome 21 (LOD [Logarithm of the Odds]  = 17), which explained the wide metabolomic variation. The locus includes 193 genes, of which 29 were involved in verbascoside synthesis and 47 showed differential expression. A homology-based analysis, using data from five high-verbascoside Lamiales species, narrowed the search to a small set of high-confidence candidate genes, including BAHD acyltransferases (BEAT, AHCT, HCBT, DAT acyltransferase family) and various cytochrome P450s (CYPs). Digital PCR confirmed the differential expression of nine candidate CYP genes. The expression of both OeCYP71D55 (a premnaspirodiene oxygenase) and the precursor-producing OeACy3G peaked at the T5 stage, 165 days after flowering. This peak mirrored the maximum time of verbascoside accumulation, suggesting that the transcriptional regulation of these CYPs is a rate-limiting factor in the pathway. This study defines a critical genetic locus and a core set of candidate genes governing verbascoside production in olive cultivars. These discoveries provide valuable molecular tools to fast-track the breeding of new olive varieties with enhanced health benefits.

The olive tree (Olea europaea L.) is a cornerstone of Mediterranean biocultural heritage, yet the shift toward intensive monoculture threatens its vast genetic diversity. This study presents a comprehensive molecular characterization of 347 olive accessions, including 172 monumental trees, from the Calabria and Basilicata regions of Southern Italy. Utilizing 10 nuclear SSR markers and chloroplast (cp-SSR) genotyping, we explored genetic diversity and maternal inheritance. Furthermore, we employed a novel diagnostic marker targeting the GA2ox-S gene, the functional determinant of the diallelic self-incompatibility (DSI) system, to assign genotypes to reproductive groups G1 and G2. Our results identified 114 unique genotypes, representing a significant reservoir of uncatalogued traditional germplasm. Notably, we discovered three instances of putative polyploidy in indigenous Calabrian olives, a rarity for the species typically considered diploid. Comparative analysis with an international dataset revealed a highly admixed genetic structure, with local genotypes showing strong affinity to Algerian and Greek pools while remaining distinct from Western Mediterranean and Middle Eastern clusters. Systematic genotyping of both canopies and rootstocks provided genetic evidence consistent with historical grafting practices in 34 instances. We observed a clear structural and maternal partition: cultivated canopies predominantly belonged to the E1 (Eastern) lineage, while uncultivated rootstocks preserved the indigenous E2 (Central-Western) maternal heritage. Reproductive screening revealed a regional dichotomy: the G1 group dominates in Basilicata, while the G2 group is more prevalent among Calabrian landraces. These findings underscore how historical agricultural practices, grafting elite clones onto resilient wild oleasters, clonal propagation, and DSI-driven obligate outcrossing have synergistically shaped the high heterozygosity of Southern Italian groves. This work provides valuable genetic resources for conservation and future breeding programs aimed at exploring resilience against climate change and emerging pathogens.

This study evaluated the flushing performance of a commercial dripline system (Toro Neptune PC 16 mm) through indoor and outdoor experiments to determine the optimal flow conditions for sediment removal. Indoor tests demonstrated that flow rates of 6.3-9.8 L/min (velocities of 0.8-1.1 m/s) effectively detached particles, with the jet throw distance serving as a practical indicator of flushing efficiency. Outdoor trials revealed that increased flow during flushing resulted in head losses and pressure drops below the anti-drip threshold, leading to emitter shutdown and a reduction in dripline length by up to 20%. To improve performance, hydraulic simulations recommended shortening the dripline by 10% and increasing the nominal pressure by 0.1 MPa. These adjustments enhanced the pressure distribution and maintained emitter functionality, improving the overall flushing performance.

Olive (Olea europaea L.) is one of the most important crop trees, with olive oil being a key ingredient of the Mediterranean diet. Oleuropein, an oleoside-type secoiridoid, is the major determinant of flavor and quality of olive oil. Iridoid biosynthesis has been elucidated in Catharanthus roseus, which produces secologanin-type secoiridoids, but iridoid biosynthesis in other species remains unresolved. In this work, we sequenced RNA from olive fruit mesocarp of six commercial olive cultivars with varying oleuropein content, during maturation and ripening. Using this data we discovered three polyphenol oxidases with oleuropein synthase (OS) activity, a novel oleoside-11-methyl ester glucosyl transferase (OMEGT) synthesizing a potential intermediate in the route, and a 7-epi-loganic acid O-methyltransferase (7eLAMT). Interestingly, integrating transcriptomics data from 15 plant species from three iridoid-producing plant orders (Lamiales, Gentianales, and Cornales), and tissue expression panels from Jasminum sambac and Fraxinus excelsior, we discovered two 2-oxoglutarate dependent dioxygenases (named 7eLAS) that synthesize 7-epi-loganic acid; in contrast C. roseus 7-deoxy-loganic acid hydroxylase (7DLH), a known bottleneck in MIA production, is a cytochrome p450. This comparative co-expression method, which combines guilt by association and comparative transcriptomics approaches, can successfully leverage big datasets for untargeted discovery of enzymes. ### Competing Interest Statement The authors have declared no competing interest.

IntroductionThe epidemic spread of the harmful bacterium Xylella fastidiosa causing the “olive quick decline syndrome”, decimating olive trees in southern Italy, in the region of Apulia, prompted investigations to search for olive genotypes harbouring traits of resistance.MethodsA prospecting survey was carried out to identify, in the heavily infected area of Apulia, olive genotypes bearing resistance. Given the limited genetic diversity in the commercial olive groves with few cultivars widely cultivated, surveys targeted predominantly spontaneous olive genotypes in natural and uncultivated areas. Trees, selected for the absence of symptoms, were subjected to diagnostic tests and parentage analysis to disclose their genetic background. Transcriptomic analyses were also employed to decipher the molecular pathways in resistant genotypes. Artificial inoculations were carried out to confirm the resistant phenotypes of four open-pollinated seedlings of the cultivar Leccino.ResultsAmong the 171 olive collected genotypes, 139 had unique simple sequence repeat (SSR) profiles, with the cultivars Leccino, Cellina di Nardò, and Ogliarola salentina being the most frequent candidate parents. Among the Leccino progeny (n. 61), 67% showed a highly resistant (HR), resistant (R), or tolerant (T) phenotype to infection by X. fastidiosa. The occurrence of such phenotypes among those deriving from Cellina di Nardò and Ogliarola salentina was 32% and 49%, respectively. Analyses of the transcriptomic profiles of three Leccino-bearing genotypes, naturally infected and not showing symptoms, unravelled that a total of 17,227, 13,031, and 4,513 genes were found altered in the expression, including genes involved in photosynthesis, cell wall, or primary and secondary metabolism.DiscussionIndeed, transcriptomic analyses showed that one of these genotypes (S105) was more resilient to changes induced by the natural bacterial infection than the remaining two (S215 and S234). This study consolidates the evidence on the presence and heritage of resistance traits associated with the cv. Leccino. Moreover, valuable insights were gathered when analysing their transcriptomic profiles, i.e., genes involved in mechanisms of response to the bacterium, which can be used in functional genetic approaches to introduce resistance in susceptible cultivars and initiate strategies in olive-breeding programs through marker-assisted selection.

In flowering plants, outcrossing is commonly ensured by self-incompatibility (SI) systems. These can be homomorphic (typically with many different allelic specificities) or can accompany flower heteromorphism (mostly with just two specificities and corresponding floral types). The SI system of the Oleaceae family is unusual, with the long-term maintenance of only two specificities but often without flower morphology differences. To elucidate the genomic architecture and molecular basis of this SI system, we obtained chromosome-scale genome assemblies of Phillyrea angustifolia individuals and related them to a genetic map. The S-locus region proved to have a segregating 543-kb indel unique to one specificity, suggesting a hemizygous region, as observed in all distylous systems so far studied at the genomic level. Only one of the predicted genes in this indel region is found in the olive tree, Olea europaea, genome, also within a segregating indel. We describe complete association between the presence/absence of this gene and the SI types determined for individuals of seven distantly related Oleaceae species. This gene is predicted to be involved in catabolism of the gibberellic acid (GA) hormone, and experimental manipulation of GA levels in developing buds modified the male and female SI responses of the two specificities in different ways. Our results provide a unique example of a homomorphic SI system, where a single conserved gibberellin-related gene in a hemizygous indel underlies the long-term maintenance of two groups of reproductive compatibility.

The ancient olive trees are the living proof of the very long tradition of cultivation, and, in most cases, their genotyping has revealed strong differences with the actual known olive varieties. Thus, in addition to their historical and cultural significance, old olives offer horticultural interest due to their genetic potential, constituting an un-exploited reservoir of olive diversity. Moreover, in the last decades several ancient orchards were abandoned generating dramatic scenarios at social, landscape and biodiversity levels. To highlight the importance of abandoned olive trees, a deep restoration was made in an Island well known for the tourism as Capri, which was important in the past for agropastoral activities. The different morphologies detected after orchards cleaning together with the huge dimensions of some olive trees, had open the possibility to seek for the ancient olive cultivation in the Capri Island. The molecular identification of both canopy and rootstock through SSR markers of 67 accessions, highlight the existence of twenty-one ancient genotypes in this island. Two of these were corresponded to the Italian and Greek known cultivars while the genetic identity of remained genotypes resulted unique, even have been compared genetically with more than 450 worldwide olive cultivars. Molecular identification has demonstrated that some of them were clonally propagated and only in two cases, the grafting scenario has been discovered. Age determination by radiocarbon (14C) dating and specific algebraic formulas, shed light on the centennial age of analyzed trees, meaning that they probably represent remnants of ancient olive cultivations, since hundreds of years ago. The outstanding performance of these trees makes really promising their agronomical evaluation and possible use in future olive breeding programs. Their ongoing propagation will avoid losing this priceless olive germplasm and will re-constitute olive orchards with autochthonous and well-adapted varieties in the Capri Island restarting the extra virgin olive oil production after decades of abandonment.

BACKGROUND:Olive is one of the most cultivated species in the Mediterranean Basin and beyond. Despite being extensively studied for its commercial relevance, the origin of cultivated olive and the history of its domestication remain open questions. Here, we present a genealogical and kinship relationships analysis by mean of chloroplast and nuclear markers of different genera, subgenus, species, subspecies, ecotypes, cultivated, ancient and wild types, which constitutes one of the most inclusive research to date on the diversity within Olea europaea species. A complete survey of the variability across the nuclear and plastid genomes of different genotypes was studied through single nucleotide polymorphisms, indels (insertions and deletions), and length variation.RESULTS:Fifty-six different chlorotypes were identified among the Oleaceae family including Olea europaea, other species and genera. The chloroplast genome evolution, within Olea europaea subspecies, probably started from subsp. cuspidata, which likely represents the ancestor of all the other subspecies and therefore of wild types and cultivars. Our study allows us to hypothesize that, inside the subspecies europaea containing cultivars and the wild types, the ancestral selection from var. sylvestris occurred both in the eastern side of the Mediterranean and in the central-western part of Basin. Moreover, it was elucidated the origin of several cultivars, which depends on the introduction of eastern cultivars, belonging to the lineage E1, followed by crossing and replacement of the autochthonous olive germplasm of central-western Mediterranean Basin. In fact, our study highlighted that two main 'founders' gave the origin to more than 60% of analyzed olive cultivars. Other secondary founders, which strongly contributed to give origin to the actual olive cultivar diversity, were already detected.CONCLUSIONS:The application of comparative genomics not only paves the way for a better understanding of the phylogenetic relationships within the Olea europaea species but also provides original insights into other elusive evolutionary processes, such as chloroplast inheritance and parentage inside olive cultivars, opening new scenarios for further research such as the association studies and breeding programs.

The bioactive properties of olive (Olea europaea) fruits and olive oil are largely attributed to terpenoid compounds, including diverse triterpenoids such as oleanolic, maslinic and ursolic acids, erythrodiol, and uvaol. They have applications in the agri-food, cosmetics, and pharmaceutical industries. Some key steps involved in the biosynthesis of these compounds are still unknown. Genome mining, biochemical analysis, and trait association studies have been used to identify major gene candidates controlling triterpenoid content of olive fruits. Here, we identify and functionally characterize an oxidosqualene cyclase (OeBAS) required for the production of the major triterpene scaffold β-amyrin, the precursor of erythrodiol, oleanolic and maslinic acids, and a cytochrome P450 (CYP716C67) that mediates 2α oxidation of the oleanane- and ursane-type triterpene scaffolds to produce maslinic and corosolic acids, respectively. To confirm the enzymatic functions of the entire pathway, we have reconstituted the olive biosynthetic pathway for oleanane- and ursane-type triterpenoids in the heterologous host, Nicotiana benthamiana. Finally, we have identified genetic markers associated with oleanolic and maslinic acid fruit content on the chromosomes carrying the OeBAS and CYP716C67 genes. Our results shed light on the biosynthesis of olive triterpenoids and provide new gene targets for germplasm screening and breeding for high triterpenoid content.

A major concern for olive cultivation in many extra-Mediterranean regions is the adaptation of recently introduced cultivars to environmental conditions different from those prevailing in the original area, such as the Mediterranean basin. Some of these cultivars can easily adapt their physiological and biochemical parameters in new agro-environments, whereas others show unbalanced values of oleic acid content. The objective of this study was to evaluate the effects of the thermal regime during oil synthesis on the expression of fatty acid desaturase genes and on the unsaturated fatty acid contents at the field level. Two cultivars (Arbequina and Coratina) were included in the analysis over a wide latitudinal gradient in Argentina. The results suggest that the thermal regime exerts a regulatory effect at the transcriptional level on both OeSAD2 and OeFAD2-2 genes and that this regulation is cultivar-dependent. It was also observed that the accumulated thermal time affects gene expression and the contents of oleic and linoleic acids in cv. Arbequina more than in Coratina. The fatty acid composition of cv. Arbequina is more influenced by the temperature regime than Coratina, suggesting its greater plasticity. Overall, findings from this study may drive future strategies for olive spreading towards areas with different or extreme thermal regimes serve as guidance for the evaluation olive varietal patrimony.

Water management is a key factor to optimize fruit quality and yield of processing tomatoes which are site-specific and influenced by environmental conditions e.g., soil, temperature, precipitation. The aim of this study was to evaluate the efficacity of a low-cost wireless soil moisture sensor in determining the irrigation level for optimizing the marketable yield, fruit quality and economic profit of processing tomato. A two-years (2017–2018) trial was conducted in open field, applying nine drip irrigation levels controlled by wireless soil moisture capacitance sensors. The irrigation levels were as follows: 13.2, 16.7, 25.4, 33.3, 50.0, 62.3, 82.5, 100 and 186.8% of water restitution based on soil moisture sensor readings. Because of the crop stress induced by heavy rainfalls occurring in 2018 growing season, total and marketable yields reached higher maximum values in 2017 than 2018. In 2017, total and marketable yields were maximized by supplying 92.8% and 96.2% of irrigation level, respectively. Moreover, 95.6% and 91.2% of irrigation level were necessary in 2018 to maximize total and marketable yield, respectively. In both growing seasons, marketable yield variation was due to changes of both fruit number and fruit mean weight. Total soluble solids of fruit juice linearly decreased by increasing the irrigation level with a more pronounced effect in the driest growing season (2017). Economic analysis demonstrated that 100% of irrigation level should be preferred by the Italian farmers since it maximized the operating margins of processing tomatoes in both years. To conclude, the use of the tested low-cost wireless soil moisture sensor is an effective tool to manage the level of irrigation and optimize the processing tomato yield and economic benefits for farmers.

Olive (Olea europaea L.) is one of the most cultivated tree species in Iran. This plant is characterized by its tolerance to drought, salt, and heat stresses while being vulnerable to frost. During the last decade, periods of frost have occurred several times in Golestan Province, in the northeast of Iran, which caused severe damage to olive groves. This study aimed to evaluate and individuate autochthonous Iranian olive varieties with regard to frost tolerance and good agronomic performance. For this purpose, 218 frost-tolerant olive trees were selected from 150,000 adult olive trees (15-25 years old), following the last harsh autumn of 2016. The selected trees were reassessed at different intervals, i.e., 1, 4, and 7 months after the cold stress in field conditions. Using 19 morpho-agronomic traits, 45 individual trees with relatively stable frost-tolerance were reevaluated and selected for this research. Ten highly discriminating microsatellite markers were used for the genetic profiling of the 45 selected olive trees, and, ultimately, five genotypes with the highest tolerance among 45 selected ones were placed in a cold room at freezing temperatures for image analyses of cold damage. The results of morpho-agronomic analyses evidenced no bark splitting or symptoms of leaf drop in the 45 cold-tolerant olives (CTOs). The oil content of the cold-tolerant trees comprised almost 40% of the fruit dry weight, highlighting the potential of these varieties for oil production. Moreover, through molecular characterization, 36 unique molecular profiles were individuated among the 45 analyzed CTOs that were genetically more similar to the Mediterranean olive cultivars than the Iranian ones. The present study demonstrated the high potential of local olive varieties, which would be promising and more suitable than commercial olive varieties, with regard to the establishment of olive groves under cold climate conditions. This could be a valuable genetic resource for future breeding activities to face climate changes.

A prospecting campaign in the Maltese Islands has ensured the survival of several ancient olive trees (Olea europaea L.), genetically distant from known cultivars. Most of these plants were abandoned or partially cultivated. A two-year evaluation of fruit characteristics and compositions was performed on samples collected from the main representatives of these indigenous genotypes. Analyses were carried out using Gas Chromatography, High-Performance Liquid Chromatography and Near Infrared Spectrometry. Among the fruit samples, a wide range of variations was observed. Some of the genotypes showed fruit traits suitable for table olive production. This is the case of samples with a pulp/pit ratio higher than four, such as 1Wardija, 1Caritas, 1Plattini, 1Bingemma Malta and 3Loretu, whilst 1Bidni, 1Mellieha, 2Qnotta, 3Loretu, 1Bingemma Malta and 1Caritas were suitable for dual purpose. The total phenol content ranged from 6.3 (1Wardija) to 117.9 (2Mtarfa) g/kg of fresh pulp. The average percentage of MUFA was quite low for most of the varieties. These genotypes, which presumably originated in the Maltese Islands and are well adapted to the local pedo-climatic conditions, are being propagated for the following evaluation of their bio-agronomical performance (production, suitability to intensive cultivation, environmental sustainability, product quality, etc.). The purpose is to select, among these local genotypes, the most outstanding varieties, in terms of phenolic and FA profile and agronomical potential, to spread into cultivation, thereby contributing to an increase in the quality of the local table and olive oil production, strongly linked to the territory.

BackgroundOlive oil contains monounsaturated oleic acid up to 83% and phenolic compounds, making it an excellent source of fat. Due to its economic importance, the quantity and quality of olive oil should be improved in parallel with international standards. In this study, we analyzed the raw RNA-seq data with a meta-analysis approach to identify important genes and their metabolic pathways involved in olive oil quality.ResultsA deep search of RNA-seq published data shed light on thirty-nine experiments associated with the olive transcriptome, four of these proved to be ideal for meta-analysis. Meta-analysis confirmed the genes identified in previous studies and released new genes, which were not identified before. According to the IDR index, the meta-analysis had good power to identify new differentially expressed genes. The key genes were investigated in the metabolic pathways and were grouped into four classes based on the biosynthetic cycle of fatty acids and factors that affect oil quality. Galactose metabolism, glycolysis pathway, pyruvate metabolism, fatty acid biosynthesis, glycerolipid metabolism, and terpenoid backbone biosynthesis were the main pathways in olive oil quality. In galactose metabolism, raffinose is a suitable source of carbon along with other available sources for carbon in fruit development. The results showed that the biosynthesis of acetyl-CoA in glycolysis and pyruvate metabolism is a stable pathway to begin the biosynthesis of fatty acids. Key genes in oleic acid production as an indicator of oil quality and critical genes that played an important role in production of triacylglycerols were identified in different developmental stages. In the minor compound, the terpenoid backbone biosynthesis was investigated and important enzymes were identified as an interconnected network that produces important precursors for the synthesis of a monoterpene, diterpene, triterpene, tetraterpene, and sesquiterpene biosynthesis.ConclusionsThe results of the current investigation can produce functional data related to the quality of olive oil and would be a useful step in reducing the time of cultivar screening by developing gene specific markers in olive breeding programs, releasing also new genes that could be applied in the genome editing approach.

Fruit and crop cultivation represents the main food source and produce important incomes in many countries worldwide but, in many cases, they can cause soil erosion and lead to extreme land degradation. Understanding and quantifying the impact of land use on soil erosion is essential to achieve sustainable land management. In Umbria region in Central Italy, olive and tobacco are two of the most profitable crops, spread on the slopes of mountains and hills or in the Tiber river valley, respectively. In particular, tobacco production, spread in the last decades along the plains and foothills of the northern part of the region, posed serious threats to the ecosystem, causing soil erosion and representing an alarming source of chemical pollution. In this study, the environmental advantages of replacing tobacco crop with perennial olive groves were evaluated. For this purpose, a method is proposed, initially, to evaluate land suitability for olive cultivation based on machine learning methods and on a set of geomorphological and climatic variables, and then to evaluate the impact of land use conversion from arable crops to olive groves on soil erosion, using LANDPLANER model and considering different rainfall scenarios. LANDPLANER is able to estimate the effects of rainfall on the triggering of landslides and erosion processes and their competition on the slopes. Results show that such conversion is sustainable for more than 40% of the current tobacco production area and it may reduce soil erosion up to 50%. This study provides a framework that starting from a statistical model for land evaluation for new agricultural purposes, assesses the impact of land use change on soil erosion. It provides a method useful to promote a sustainable use of soil, taking into account also effects of agricultural changes effect on soil erosion and degradation.

Extra virgin olive oil (EVOO) is the best vegetable oil worldwide but, at the same time, is one of the product victims of fraud in the agri-food sector, and the differences about quality within the extra-virgin olive oil category are often missed. Several scientific techniques were applied in order to guarantee the authenticity and quality of this EVOO. In the present study, the volatile compounds (VOCs) by gas chromatography–mass spectrometry with solid-phase micro-extraction detection (GC–MS SPME), organoleptic analysis by the official Slow Food panel and the detection by a Small Sensor System (S3) were applied. Ten EVOOs from Umbria, a central Italian region, were selected from the 2021 Slow Food Italian extra virgin olive oil official guide, which includes hundreds of high-quality olive oils. The results demonstrated the possibility to discriminate the ten EVOOs, even if they belong to the same Italian region, by all three techniques. The result of GC–MS SPME detection was comparable at the discrimination level to the organoleptic test with few exceptions, while the S3 was able to better separate some EVOOs, which were not discriminated perfectly by the other two methods. The correlation analysis performed among and between the three methodologies allowed us to identify 388 strong associations with a p value less than 0.05. This study has highlighted how much the mix of VOCs was different even among few and localized EVOOs. The correlation with the sensor detection, which is faster and chipper compared to the other two techniques, elucidated the similarities and discrepancies between the applied methods.

Some olive cultivars and production regions around the world, although they may provide good quality olive oils, may not comply with the current commercial regulations establishing acceptable levels of sterols in extra virgin olive oils. The present study was driven by the hypothesis that olive growing environments, differing in thermal regime conditions, affect squalene and sterol contents of olive fruits. On the basis of differences in agronomic characteristics and oil composition, two olive cultivars (Arbequina and Coratina) were selected and sampled at different fruit development stages. Various models were examined to look for relationships between environmental thermal records and chemical parameters; those including the accumulated thermal time (ATT) and minimum temperatures showed the best fit. In both cultivars, the total and individual sterol contents were positively associated with ATT over all the fruit development and ripening period considered. In all cases, the data from Arbequina fit the models better than for Coratina and differences between cultivars in individual sterol contents were greater in the warmest growing environments. Overall, findings indicated a strong impact of the growing environment on squalene and sterol contents. Such an effect was associated with specific thermal characteristics of the olive growing sites; concentrations were found to be higher in the warmer northernmost sites than in the cooler southernmost ones. There was also an effect of the cultivar, particularly on the contents of β-sitosterol, campesterol and total sterols. These latter results suggest greater sensitivity of sterol metabolism to temperature in cv. Arbequina.

The health, therapeutic, and organoleptic characteristics of olive oil depend on functional bioactive compounds, such as phenols, tocopherols, squalene, and sterols. Genotype plays a key role in the diversity and concentration of secondary compounds peculiar to olive. In this study, the most important bioactive compounds of olive fruit were studied in numerous international olive cultivars during two consecutive seasons. A large variability was measured for each studied metabolite in all 61 olive cultivars. Total phenol content varied on a scale of 1–10 (3831–39,252 mg kg−1) in the studied cultivars. Squalene values fluctuated over an even wider range (1–15), with values of 274 to 4351 mg kg−1. Total sterols ranged from 119 to 969 mg kg−1, and total tocopherols varied from 135 to 579 mg kg−1 in fruit pulp. In the present study, the linkage among the most important quality traits highlighted the scarcity of cultivars with high content of at least three traits together. This work provided sound information on the fruit metabolite profile of a wide range of cultivars, which will facilitate the studies on the genomic regulation of plant metabolites and development of new olive genotypes through genomics-assisted breeding.

A comprehensive effort was devoted to exploring, collecting and characterizing the local Maltese olive germplasm, often represented by ancient, monumental trees and by plants of uncertain origin. SSR and cp-SSR analysis of all samples enabled the identification of 46 genotypes and establishment of the correspondence between ancient trees, main local varieties and other Mediterranean cultivars. The application of plastid markers enabled identification of two lineages among Maltese genotypes, with more than 50% represented by lineage E2. Twenty-nine cases of grafting were identified among the various genotypes and lineages. In most cases, E1 canopies were grafted on E2 rootstocks, but reverse cases were also observed. The phylogenetic study of Maltese genotypes, together with hundreds of cultivars from the Mediterranean Basin and beyond, highlights the richness of Maltese olive diversity and drawing attention to the genetic similarity of some Maltese olive genotypes with neighboring Italian and Algerian varieties. These results underline the long-lasting presence of the olive in the country, contributing to the reconstruction of its phylogeny and demonstrating a possible autochthonous origin of many samples. Some still-living ancient trees are at serious risk of extinction due to abandonment, urban expansion and environmental threats. This study supports the preservation of the Maltese olive germplasm and highlights its importance as a rich genetic source to face new agronomical challenges and future climatic constraints.