Olive Germplasm Research Articles

Characterization and evaluation of olive germplasm in southern Italy

The southern Italian region of Campania has suitable pedo-climatic conditions and a large varietal heritage able to produce oils with high typicality. The aim of this study was to characterize 20 cultivars belonging to Campania's olive germplasm, evaluating their vegetative and production aspects and their oil quality characteristics. The study was conducted from 2003 to 2009, observing the following aspects in six plants per variety: entry into production, vigour, ripening and drupe oil content. The following analyses were carried out on monovarietal oils, obtained by microextractor: acid composition, polyphenol content and aromatic profile. The agronomic results showed early entry into production for the cultivars Racioppella, Ortolana, Biancolilla and Carpellese. However, entry into production was delayed for Ritonnella, Ortice, Cornia and Rotondella. As regards vegetative behaviour, Asprinia, from the province of Caserta and Pisciottana and Carpellese, from the province of Salerno, proved the most vigorous cultivars. Groups of similar cultivars emerged from chemical and sensory analysis of their oils, while other accessions were well characterized and separated from each other, showing a high level of diversity and specificity.

Intraspecific variation in pollen viability, germination and ultrastructure of Olea europaea L.

Variability of pollen morphology and ultrastructure of Olea europaea L. ( Oleaceae ) cultivars ‘Koroneiki’, ‘Mastoidis’ and ‘Kalamata’ was studied with scanning electron microscopy to identify genotype- distinguishing characters that could be employed for morphological cultivar discrimination. Pollen viability and germination was also measured for the three cultivars. Significant variation was observed in minimum diameter, maximum/minimum diameter (L/W) ratio and size index of pollen grain of ‘Mastoidis’ and the other two cultivars. Regarding the exine pattern, muri width of ‘Koroneiki’ and ‘Mastoidis’ pollen was similar and significantly lower than that of ‘Kalamata’. The highest values of maximum diameter were observed in ‘Kalamata’ and differed significantly with ‘Mastoidis’ but not with ‘Koroneiki’. No marked variation was noted in minimum diameter and L/W ratio. ‘Kalamata’ was characterized by higher size index than the other two cultivars, though statistical difference was observed only when compared with ‘Mastoidis’. Higher pollen viability and in vitro germination was recorded for ‘Kalamata’ and ‘Mastoidis’ compared to ‘Koroneiki’. Acquired information could contribute to the establishment of a database for future olive germplasm classification studies. Keywords: Floral biology, olive, pollen ultrastructure, scanning electron microscopy

Characterization of olive germplasm by chemical oil components and morphological descriptors in Basilicata region (Italy)

In this paper, we describe variations among autochthonous olive cultivars from five different areas in Basilicata (Southern Italy) classified according to 33 chemical oil components and morphological traits. While all examined descriptors show no significant differences among cultivars, means and coefficients of variations have been highlighted. Principal component analysis has then been used to reduce the number of descriptors. Cultivars have been classified by cluster analysis into three groups. Following a discussion of cultivar group similarities, results suggest that an ‘a priori’ classification of cultivars according to growing area does not strictly correspond to phenotypic grouping. From the spatial distribution of cultivars, however, it has been possible to identify ‘superior’ genotypes in terms of olive oil composition.

FULL CHARACTERIZATION OF VIRGIN OLIVE OILS FROM NEW OLIVE GERMPLASM

The products from a new olive germplasm have been studied. Up to now, nine oil varieties from new Olea oleuropaea L. genotypes (P5 93, P5 18, P1 3, P1 25, G1 127, P1 35, P4 6, G2 121 and P6 73) have been characterised. They exhibited different analytical and sensory traits but were in general all interesting for their flavour, aroma, stability, endurance to oxidation and potentially long shelf-life. They mostly showed significant levels of functional micro-components, such as biophenolics, o-diphenols, tocopherols, volatiles, carotenes and other carotenoids and xanthophylls (lutein noticeably). Most of the other analytical variables evaluated were barely affected by the genetic store. Based on analytical datasets the new olive genotypes were well discriminated by multivariate methods.

MORPHOLOGICAL LIMITATIONS IN FLORAL DEVELOPMENT AMONG OLIVE TREE CULTIVARS

ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Plant Physiology from Cell to Fruit Production System MORPHOLOGICAL LIMITATIONS IN FLORAL DEVELOPMENT AMONG OLIVE TREE CULTIVARS

Characterization of Profilin Polymorphism in Pollen with a Focus on Multifunctionality

Profilin, a multigene family involved in actin dynamics, is a multiple partners-interacting protein, as regard of the presence of at least of three binding domains encompassing actin, phosphoinositide lipids, and poly-L-proline interacting patches. In addition, pollen profilins are important allergens in several species like Olea europaea L. (Ole e 2), Betula pendula (Bet v 2), Phleum pratense (Phl p 12), Zea mays (Zea m 12) and Corylus avellana (Cor a 2). In spite of the biological and clinical importance of these molecules, variability in pollen profilin sequences has been poorly pointed out up until now. In this work, a relatively high number of pollen profilin sequences have been cloned, with the aim of carrying out an extensive characterization of their polymorphism among 24 olive cultivars and the above mentioned plant species. Our results indicate a high level of variability in the sequences analyzed. Quantitative intra-specific/varietal polymorphism was higher in comparison to inter-specific/cultivars comparisons. Multi-optional posttranslational modifications, e.g. phosphorylation sites, physicochemical properties, and partners-interacting functional residues have been shown to be affected by profilin polymorphism. As a result of this variability, profilins yielded a clear taxonomic separation between the five plant species. Profilin family multifunctionality might be inferred by natural variation through profilin isovariants generated among olive germplasm, as a result of polymorphism. The high variability might result in both differential profilin properties and differences in the regulation of the interaction with natural partners, affecting the mechanisms underlying the transmission of signals throughout signaling pathways in response to different stress environments. Moreover, elucidating the effect of profilin polymorphism in adaptive responses like actin dynamics, and cellular behavior, represents an exciting research goal for the future.

Development of DArT markers in olive (Olea europaea L.) and usefulness in variability studies and genome mapping

The present study reports the setting up of Diversity Arrays Technology (DArT) markers in olive (Olea europaea L.). Two genomic representations were generated using the PstI/TaqI combination. A first one was aimed to cover the variability available at the World Olive Germplasm Bank (WOGB) and it was based on DNA from 87 olive cultivars carefully selected from the WOGB to represent the olive variability. The second one was obtained from DNA of the parents of a mapping population, ‘Picual’ and ‘Arbequina’, and was used to increase the number of markers segregating within them. A total of 2031 and 1630 markers were used for diversity and mapping analyses, respectively to test the utility of DArT markers in olive. A set of 62 cultivars was genotyped with olive-specific DArT markers. A dendrogram was constructed confirming the relationships among olive cultivars reported in previous works. Besides, DArT markers permitted the unambiguous discrimination of all 62 genotypes confirming thus their utility for identification studies, an important issue for management of germplasm collections. DArT markers also allowed the construction of a genetic map of olive using the population derived from the cross ‘Picual’בArbequina’ and the pseudo-testcross mapping strategy. This map will be used as a framework map to add new markers derived from olive sequencing originating from the project OLEAGEN. In conclusion, olive-specific DArT markers will enhance identification and genetic studies in olive given their high throughput and low cost per data.

Polyphenol characterization and antioxidant evaluation of Olea europaea varieties cultivated in Cilento National Park (Italy)

Over time, a large number of cultivars of Olea europaea, one of the oldest cultivated trees in the world, appeared as a result of events such as outcrossing, mutation, and selective pressure (including grower requirements) on the original olive germplasm. Some cultivars are characteristic of a particular country, whereas others are scattered over an area of cultivation. In the Cilento and Vallo di Diano National Park, numerous olive varieties are grown as the native cultivars ‘Pisciottana’, ‘Rotondella’, and ‘Salella’, the varieties ‘Frantoio’ and ‘Biancolilla’, widely cultivated in Southern Italy, and a new variety, known as ‘FS17’, obtained by self-pollination of ‘Frantoio’ cultivar. In order to assess the phenolic composition of these cultivars, metabolomic techniques (1D and 2D NMR, and HPLC analyses) were extensively applied. 1H-NMR spectral data were processed and analyzed by Principal Component Analysis (PCA) to point out possible differences in polyphenol composition between the cultivars. The radical scavenging capacity of the investigated cultivars was also evaluated through 2,2-diphenyl-1-picrylydrazyl (DPPH). Folin–Ciocalteu reagent was used to estimate the total phenolic content. The cultivar ‘FS17’ showed lower total polyphenol content and antioxidant activity than the other analyzed varieties.

Worldwide Core Collection of Olive Cultivars Based on Simple Sequence Repeat and Morphological Markers

ABSTRACTCore collections reflecting the diversity of large germplasm collections are valuable tools to conserve and evaluate the genetic resources more effectively. Three strategies using two different search algorithms were trained to develop the most representative nested core collection of the World Olive Germplasm Bank (WOGB) of Cordoba (Spain), the largest and best characterized collection of olive (Olea europaea L.) cultivars worldwide. The original dataset was composed of 378 olive accessions from 21 different countries characterized by 14 microsatellite markers (simple sequence repeats [SSRs]). Each nested core collection included five subsets representing different percentages of the base collection (5, 10, 15, 20, and 30%). The strategy maximizing the allele coverage implemented in the software Core Hunter was chosen as the best. The five subsets developed by this method captured the maximum number of alleles showing fewer significant differences in their frequencies with respect to the whole collection. Additionally, a balanced geographical composition was observed in the nested subsets in spite of the strong overrepresentation of western Mediterranean accessions present in the WOGB. The results of this study are aimed at improving both the conservation and management of olive genetic resources and the study of differential genotype × environment interactions by testing a minimum number of accessions

Characterisation and identification of olive cultivars from North-eastern Algeria using molecular markers

SummaryIn the present study, ten microsatellite (simple sequence repeat; SSR) and seven single nucleotide polymorphism (SNP) markers were used to characterise a set of 14 cultivars of olive (Olea europaea L.) from North-eastern Algeria. The genetic profiles of these cultivars were compared with two Tunisian, one Moroccan, and two Algerian cultivars. A total of 77 alleles were amplified for the SSR markers. The mean values of the expected heterozygosity (He), the observed heterozygosity (Ho), and the polymorphic information content (PIC) values were 0.806, 0.851, and 0.752, respectively. A combination of three SSR loci (ssrOeUA-DCA9, ssrOeUA-DCA18, and UDO099-043) permitted the identification of all 14 olive accessions analysed. Although less polymorphic than the SSR markers, the SNP markers used in this study showed relatively high diversity values. The mean He value was 0.374. The same value was obtained for the Ho, and PIC values ranged from 0.373 (Cycl-1) to 0.117 (LS2). Eleven out of all 19 olive cultivars (63%) were identified by means of the SNP markers, confirming the value of the differences from SSR markers in terms of their efficiency for cultivar discrimination and stressing the need to develop more SNP markers. The results obtained in this work highlight the rich genetic diversity available in even a small set of olive germplasm from Algeria and confirm the utility of SSR and SNP markers for genotyping olive cultivars.

Developing a core collection of olive (Olea europaea L.) based on molecular markers (DArTs, SSRs, SNPs) and agronomic traits

Molecular markers (SSR, SNP and DArT) and agronomical traits have been used in the world’s largest olive (Olea europaea L.) germplasm collection (IFAPA, Centre Alameda del Obispo, Cordoba, Spain) to study the patterns of genetic diversity and underlying genetic structure among 361 olive accessions. In addition the marker data were used to construct a set of core collections by means of two different algorithms (MSTRAT and PowerCore) based on M (maximization) strategy. Our results confirm that the germplasm collection is a useful source of genetically diverse material. We also found that geographical origin is an important factor structuring genetic diversity in olive. Subsets of 18, 27, 36, 45 and 68 olive accessions, representing respectively 5%, 7.5%, 10%, 12.5% and 19% of the whole germplasm collection, were selected based on the information obtained by all the data set as well as each marker type considered individually. According to our results, the core collections that represent between 19% and 10% of the total collection size could be considered as optimal to retain the bulk of the genetic diversity found in this collection. Due to its high efficiency at capturing all the alleles/traits states found in the whole collection, the core size of 68 accessions could be of special interest for genetic conservation applications in olive. The high average genetic distance and diversity and the almost equal representation of accessions from different geographical regions indicate that the core size of 36 accessions, could be the working collection for olive breeders.

Nematode community populations in the rhizosphere of cultivated olive differs according to the plant genotype

Classical and molecular methods were used to study the nematode communities associated with rhizosphere soil and roots of a collection of 16 olive cultivars from a world olive germplasm bank in Mengibar (Jaen province, southern Spain). Classical nematological analysis, including soil nematode extraction, species counting and morphological identification showed that 24 taxa belonging to 9 genera (including Aphelenchoides, Criconemoides, Ditylenchus, Filenchus, Helicotylenchus, Merlinius, Paratylenchus, Tylenchus, and Xiphinema) and 8 families (including Anguinidae, Aphelenchidae, Belonolaimidae, Criconematidae, Hoplolaimidae, Longidoridae, Tylenchidae and Tylenchulidae) of plant-parasitic nematodes were present, with one species (Helicotylenchus digonicus) being prevalent in all samples. The low values of the plant-parasitic nematode index (PPI) indicated a high disturbance of the field soil probably due to application of herbicides and fertilizers. Cluster analysis of population densities of the various nematode species, nematode trophic groups, and ecological indices grouped most olive cultivars into three main clusters indicating that olive genotypes differ in the nematode communities in their rhizosphere soil. The use of T-RFLP analysis discriminated to a higher extent the nematode communities present in the rhizosphere soil from the different olive cultivars as compared to the morphological-based analysis. This study provides the first evidence of an effect of the olive genotype on nematode community composition by combining classical morphological and molecular approaches.

Genetic structure and core collection of the World Olive Germplasm Bank of Marrakech: towards the optimised management and use of Mediterranean olive genetic resources

The conservation of cultivated plants in ex-situ collections is essential for the optimal management and use of their genetic resources. For the olive tree, two world germplasm banks (OWGB) are presently established, in Córdoba (Spain) and Marrakech (Morocco). This latter was recently founded and includes 561 accessions from 14 Mediterranean countries. Using 12 nuclear microsatellites (SSRs) and three chloroplast DNA markers, this collection was characterised to examine the structure of the genetic diversity and propose a set of olive accessions encompassing the whole Mediterranean allelic diversity range. We identified 505 SSR profiles based on a total of 210 alleles. Based on these markers, the genetic diversity was similar to that of cultivars and wild olives which were previously characterised in another study indicating that OWGB Marrakech is representative of Mediterranean olive germplasm. Using a model-based Bayesian clustering method and principal components analysis, this OWGB was structured into three main gene pools corresponding to eastern, central and western parts of the Mediterranean Basin. We proposed 10 cores of 67 accessions capturing all detected alleles and 10 cores of 58 accessions capturing the 186 alleles observed more than once. In each of the 10 cores, a set of 40 accessions was identical, whereas the remaining accessions were different, indicating the need to include complementary criteria such as phenotypic adaptive and agronomic traits. Our study generated a molecular database for the entire OWGB Marrakech that may be used to optimise a strategy for the management of olive genetic resources and their use for subsequent genetic and genomic olive breeding.Electronic supplementary materialThe online version of this article (doi:10.1007/s10709-011-9608-7) contains supplementary material, which is available to authorized users.

Variability of wild olives ( Olea europaea subsp. europaea var. sylvestris) analyzed by agro-morphological traits and SSR markers

The genetic diversity of wild olive trees sampled from eight different sites from two provinces of Andalusia (Cadiz and Jaen), Southern Spain, was evaluated by means of agro-morphological traits and SSR markers. The agro-morphological traits showed a high variation between genotypes and significant correlation coefficients were obtained among the values recorded in two consecutive years, 2007/08 and 2008/09 ( r = 0.59–0.78). Traits such as fruit symmetry (position A), stone shape, fruit flesh/stone ratio and olive oil content on both wet and dry matter, showed the highest values of diversity and were very useful in genotype discrimination. As expected, average values obtained in wild olives for fruit size and oil content were lower than the previously reported in cultivated material. However, it is noticeable that wild trees with fruit weights (1.3 g) and olive oil percentage in dry matter (33.8%) comparable to the values found in some olive cultivars, were also found. With both DNA-based and agro-morphological descriptors, higher levels of variability were found within each site than between sites. Genetic variation observed among the wild olive germplasm at the DNA level was higher than the agro-morphological traits, indicating the efficiency of SSR markers for detecting genetic diversity among wild olive genotypes and their relationships. The lack of consistency between the relationship studies performed with molecular and morphological markers could indicate that each marker system measures different aspects of the wild olive genetic variability. Molecular data obtained by SSR markers together with morphological and agronomical characterization of olive trees confirmed the high diversity within the wild populations and their potential use for olive breeding.

Levels of lipochromes and other bioactives in virgin olive oil from new olive germplasm

The composition of virgin olive oils from three new olive cultivars, such as Arno, Tevere and Basento, has been investigated in this work. Our attention was focused on chlorophylls, carotenes, xanthophylls and other major bioactives, as well as on some analytical indices related to functionality, quality and typicality of the new products. Our analytical study showed how the new oil kinds, especially Arno oil, had an interesting qualitative–quantitative composition of the pigment fraction. Pheophytin a (within the chlorophyll subfraction) and lutein (within the carotenoid subfraction) were found to be the major natural pigments occurring in the new products. Interesting were also the concentrations of biophenols, tocopherols, and tocotrienols detected in the three new oil varieties, as well as the values of the remarkable ratio fatty acids ω6/fatty acids ω3 and biophenols/polyunsaturated fatty acids (PUFA) (and those of the analytical variables endurance and susceptibility to autoxidation). The chemometric analyses showed how different multivariate methods were effective in discriminating between oil varieties. Thus, these chemometrics can effectively be used for traceability or authentication of the new products. We concluded how the three new olive cultivars can actually lead to new advances in the olive growing sector.

Genetic diversity among olive varieties of Southern Italy and the traceability of olive oil using SSR markers

SummaryTo evaluate germplasm variability and to identify DNA profiles useful for tracing the genetic identity of olive oil, we used six Simple Sequence Repeats (SSRs) in 47 cultivated olive varieties from Central and Southern Italy. A total of 80 polymorphic SSR markers were scored and both the observed heterozygosity and the polymorphic index content were, on average, high. Genetic similarities were investigated by agglomerative hierarchical clustering and principal component analysis. The results implied that most of the olive accessions from the Campania region were genetically different from those of other Italian regions. This finding was further supported by partitioning the genetic variability using analysis of molecular variance. Furthermore, we analysed the DNA isolated from the fruit and mono-varietal oils of three cultivars. Comparative analysis of the SSR profiles revealed that these were conserved in the agro-food chain, although our data also suggested that some issues, such as the sensitivity and performance of the assay in complex mixtures, may pose limitations. Our findings extend current knowledge of Italian olive germplasm and highlight the richness and specificity of the genetic resource of olives in some regions of Southern Italy. They also provide molecular information that can be exploited for the protection of genetic material and mono-varietal oils.

Genomic profiling of plastid DNA variation in the Mediterranean olive tree

BackgroundCharacterisation of plastid genome (or cpDNA) polymorphisms is commonly used for phylogeographic, population genetic and forensic analyses in plants, but detecting cpDNA variation is sometimes challenging, limiting the applications of such an approach. In the present study, we screened cpDNA polymorphism in the olive tree (Olea europaea L.) by sequencing the complete plastid genome of trees with a distinct cpDNA lineage. Our objective was to develop new markers for a rapid genomic profiling (by Multiplex PCRs) of cpDNA haplotypes in the Mediterranean olive tree.ResultsEight complete cpDNA genomes of Olea were sequenced de novo. The nucleotide divergence between olive cpDNA lineages was low and not exceeding 0.07%. Based on these sequences, markers were developed for studying two single nucleotide substitutions and length polymorphism of 62 regions (with variable microsatellite motifs or other indels). They were then used to genotype the cpDNA variation in cultivated and wild Mediterranean olive trees (315 individuals). Forty polymorphic loci were detected on this sample, allowing the distinction of 22 haplotypes belonging to the three Mediterranean cpDNA lineages known as E1, E2 and E3. The discriminating power of cpDNA variation was particularly low for the cultivated olive tree with one predominating haplotype, but more diversity was detected in wild populations.ConclusionsWe propose a method for a rapid characterisation of the Mediterranean olive germplasm. The low variation in the cultivated olive tree indicated that the utility of cpDNA variation for forensic analyses is limited to rare haplotypes. In contrast, the high cpDNA variation in wild populations demonstrated that our markers may be useful for phylogeographic and populations genetic studies in O. europaea.

Preliminary characterization and morpho-agronomic evaluation of the olive germplasm collection of the Mendoza province (Argentina)

In Mendoza, little is known about the olive germplasm, and even though there is a collection, studies about characterization and evaluation are scarce. The aims of this work were to make a morpho-agronomic characterization of the Mendoza olive collection and to identify locally adapted accessions with a good aptitude for oil production. Quantitative traits were measured in pit, fruit, inflorescence, and leave samples, and oil content, flowering and maturity days were also measured. In order to group the genetic material and evaluate the phenotypic variability, descriptive statistics, cluster analysis, and principal components analysis were used. The 61 accessions were grouped in 12 clusters based on the multivariate analysis of 19 traits. The collection featured phenotypic variability for all the studied traits, especially for the fruit fresh weight, pulp-pit ratio, and oil content on fresh weight basis. Seventeen accessions suitable for oil production were selected, seven of which could also be used for table.

Simple Sequence Repeat Identification and Endocarp Characterization of Olive Tree Accessions in a Tunisian Germplasm Collection

Most traditional olive-producing countries possess a diversified genetic patrimony in Olea europaea L. Since the emergence of modern olive growing system, the identification, classification, and conservation of autochthonous olive cultivars is a priority for these countries. In this work, a total of 84 accessions belonging to the “Boughrara”-Sfax olive germplasm collection located in Tunisia have been screened using a powerful set of eight simple sequence repeat markers (SSRs). The study revealed a high genetic variability among the collection and detected a total of 64 alleles. For better management of the mentioned germplasm bank, an improved classification of the entries, including new denominations, has been proposed. In addition, several cases of mislabeling, synonymy, and homonymy have been clarified. Genetic relationships among cultivars have been analyzed showing four major clusters. Finally, a correspondence factor analysis demonstrated that cultivars tend to cluster depending on their main use as oil or table olives. No clear clustering tendencies were observed when the geographical origin of cultivars was used as the criteria for the analysis. All results obtained by SSR screening and classification were in accordance with classification based on morphological traits of fruit endocarps.

Molecular characterization of genetic diversity, structure, and differentiation in the olive (Olea europaea L.) germplasm collection of the United States Department of Agriculture

Fifteen microsatellite loci were used to genotype 108 accessions of cultivated olive, Olea europaea L. ssp. europaea var. europaea, and eight of O. europaea L. ssp. cuspidata (Wall. ex G. Don) Ciferri, from the germplasm collection of the United States Department of Agriculture in Davis, California. Number of alleles per locus ranged from 3, for locus IAS-pOe12_A, to 16, for locus ssrOeUA-DCA11, with an overall mean of 9.93. Observed heterozygosity ranged from 0.175, for locus UDO99–019, to 0.937, for locus GAPU89, with a mean of 0.640. The cluster analysis using the Unweighted Pair Group Method using Arithmetic mean (UPGMA) method displayed thirteen clusters within seven main groups that can be partially described by common geographic origin or fruit use, though overlap among these groups was common. The locus-wise total gene diversity (H T) ranged from 0.319, at UDO99–019, to 0.847, at ssrOeUA-DCA3, with an overall mean of 0.696. Most of the gene diversity was partitioned within clusters, with proportions (H S/H T) ranging from 0.633, at IAS-pOe12_B, to 0.848 at GAPU89 per locus, with a mean of 0.759. The principal components analysis explained 24.8% of the total variation along the first two components. Projection of accessions onto the first two principal components produced affinities generally in agreement with the results of the UPGMA cluster analysis. The California cultivar ‘Mission’ clustered closely with Iberian cultivars and may represent clonal selections adapted to local growing conditions. The results show significant diversity but low levels of differentiation among olive cultivars within the collection.