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.

Whole genome scanning of a Mediterranean basin hotspot collection provides new insights into olive tree biodiversity and biology.

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

Evaluation of a dill (Anethum graveolens L.) gene bank germplasm collection using multivariate analysis of morphological traits, molecular genotyping and chemical composition to identify novel genotypes for plant breeding.

Dill (Anethum graveolens L.) is an aromatic herb widely used in the food industry, with several commercial cultivars available with different qualitative characteristics. Commercial cultivars are usually preferred over landraces due to their higher yield and also the lack of improved landraces than can be commercialized. In Greece, however, traditional dill landraces are cultivated by local communities. Many are conserved in the Greek Gene Bank and the aim here was to investigate and compare the morphological, genetic, and chemical biodiversity of twenty-two Greek landraces and nine modern/commercial cultivars. Multivariate analysis of the morphological descriptors, molecular markers, and essential oil and polyphenol composition revealed that the Greek landraces were clearly distinguished compared with modern cultivars at the level of phenological, molecular and chemical traits. Landraces were typically taller, with larger umbels, denser foliage, and larger leaves. Plant height, density of foliage, density of feathering as well as aroma characteristics were desirable traits observed for some landraces, such as T538/06 and GRC-1348/04, which were similar or superior to those of some commercial cultivars. Polymorphic loci for inter-simple sequence repeat (ISSR) and start codon targeted (SCoT) molecular markers were 76.47% and 72.41% for landraces, and 68.24% and 43.10% for the modern cultivars, respectively. Genetic divergence was shown, but not complete isolation, indicating that some gene flow may have occurred between landraces and cultivars. The major constituent in all dill leaf essential oils was α-phellandrene (54.42-70.25%). Landraces had a higher α-phellandrene and dill ether content than cultivars. Two dill landraces were rich in chlorogenic acid, the main polyphenolic compound determined. The study highlighted for the first-time Greek landraces with desirable characteristics regarding quality, yield, and harvest time suitable for breeding programs to develop new dill cultivars with superior features.

Metabolomic Fingerprinting and Molecular Characterization of the Rock Samphire Germplasm Collection from the Balkan Botanic Garden of Kroussia, Northern Greece.

The traditionally edible aerial parts of rock samphire (Crithmum maritimum L.) could be a valuable functional food or feed ingredient due to their high antioxidant capacity, ascorbic acid content, and rich content in secondary metabolites such as phenolics and flavonoids. The first objective of this study was to evaluate eighteen genotypes derived from different regions of Greece regarding the phytochemical contents of their soluble extracts in total phenolics, total flavonoids, and individual polyphenols as determined by LC-MS analysis, as well as ascorbic acid content and their antioxidant capacity as determined by different assays, including ABTS (2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid), DPPH (2,2-diphenyl-1-picrylhydrazyl radical scavenging activity), and FRAP (ferric reducing antioxidant power) assays. The second objective of the study was the molecular characterization of native Greek C. maritimum genotypes. Great variation among genotypes was observed in terms of the antioxidant capacity, ascorbic acid content, and phenolic compounds (total phenolic content and total flavonoid content), as well as in caffeolquinic acids and flavonoids. The principal component analysis highlighted genotypes with a higher potential in antioxidants and polyphenolics. The most promising genotypes were G9 from Kefalonia, followed by G4 from Ikaria, where both clearly exhibited a similar response with high values of evaluated traits. The molecular characterization of genotypes revealed low variability and low to moderate genetic diversity between populations. Our data indicated that the rock samphire germplasm collection from the Balkan Botanic Garden of Kroussia could serve as an important source of documented genetic material and, thus, it is suggested for further investigation to provide insight regarding cultivation and agro-processing aspects, artificial selection, or plant breeding aimed at developing C. maritimum genotypes of high-bioactive value.