Genetic Resources of Olea europaea L. in the Garda Trentino Olive Groves Revealed by Ancient Trees Genotyping and Parentage Analysis of Drupe Embryos

Comparison of genetic diversity between ancient and common populations of Docynia delavayi (Franch.) Schneid

Docynia delavayi (Franch.) Schneid. (D. delavayi), is a wild fruit tree which combines edible, medicinal, ecological and ornamental uses. In this study, ancient and common populations of D. delavayi were examined for genetic diversity and structure using SSR markers. As a result, a total of 136 alleles were detected at 18 SSR loci, with the mean of 7.56 alleles. The value of Na, Ne, I, He and Nm of the ancient populations were lower than those of the common populations except for Ho and Fst. It indicates that the genetic diversity of the common populations is higher than that in ancient populations. The genetic differences between ancient populations were slightly greater than those between common populations, which demonstrated less gene flow between ancient populations. According to the analysis of molecular variance (AMOVA), the genetic variation within the common population was greater than that in the ancient population, indicating that there was a higher genetic diversity within the common population. Also, the clustering heatmap results are partially consistent with the principal coordinate analysis (PCoA) results. Moreover, the mantel test showed an extremely significant correlation between genetic and geography distance (r = 0.214, p < 0.0001). Based on this work, we proposed strategies for protecting, which offers a theoretical basis for their effective utilization and conservation of D. delavayi ancient tree resources.

Development of a sustainability technical guide for the Italian olive oil supply chain

Italian olive growing must aim at the transition to economically and environmentally sustainable management systems, linked to premium quality production and to a recognized and remunerated context of biodiversity conservation in compliance with the provisions of the European Union New Green Deal and United Nations Agenda 2030. To assist and facilitate companies in this step, a sustainability technical guide for the Italian olive oil supply chain has been developed, with reference to the four pillars of sustainability. The guide, consisting of 42 requirements, was submitted to 18 olive farms from 8 different Italian regions participating in this pilot study, to assess their level of total sustainability and to receive feedbacks throughout the drafting process. Taken as a whole, the companies have proved to be virtuous in meeting the requirements provided, with percentages of compliance ranging from 86 to 96% according to pillar and from 70 to 100% according to company and showed a remarkable spirit of collaboration and involvement in the construction of the guide. In this regard, the text is aimed to represent a participatory standard for Italian institutions and for other olive countries.

Utility of EST-SNP Markers for Improving Management and Use of Olive Genetic Resources: A Case Study at the Worldwide Olive Germplasm Bank of Córdoba

Olive, the emblematic Mediterranean fruit crop, owns a great varietal diversity, which is maintained in ex situ field collections, such as the World Olive Germplasm Bank of Córdoba (WOGBC), Spain. Accurate identification of WOGBC, one of the world’s largest collections, is essential for efficient management and use of olive germplasm. The present study is the first report of the use of a core set of 96 EST-SNP markers for the fingerprinting of 1273 accessions from 29 countries, including both field and new acquired accessions. The EST-SNP fingerprinting made possible the accurate identification of 668 different genotypes, including 148 detected among the new acquired accessions. Despite the overall high genetic diversity found at WOGBC, the EST-SNPs also revealed the presence of remarkable redundant germplasm mostly represented by synonymy cases within and between countries. This finding, together with the presence of homonymy cases, may reflect a continuous interchange of olive cultivars, as well as a common and general approach for their naming. The structure analysis revealed a certain geographic clustering of the analysed germplasm. The EST-SNP panel under study provides a powerful and accurate genotyping tool, allowing for the foundation of a common strategy for efficient safeguarding and management of olive genetic resources.

Seed Paternity Analysis Using SSR Markers to Assess Successful Pollen Donors in Mixed Olive Orchards

The olive tree (Olea europaea L.) is a wind-pollinated crop that exhibits an extreme alternate bearing habit. To improve fruit set, several methods have been used to determine the most successful compatible combinations of cultivars. In this study, priority is given to seed paternity analysis based on simple sequence repeats (SSRs), microsatellite markers used for the identification of potential pollen donors of cultivar ‘Oblica’ in a mixed olive orchard during two consecutive years. Seven microsatellite primers were successfully used to examine the paternity of olive embryos from ‘Oblica’ mother trees. Embryos were considered as a product of self-fertilization if only maternal alleles were present, but not a single case of self-fertilization was found among all the embryos analyzed. Two dominant pollen donors were not the closest nor the cultivars with the highest number of trees in the orchard, suggesting that cross-compatibility may have a key role in determining pollen donor success. In our earlier studies, pollen tube growth and fertilization success correlated with fruit set when controlled crosses between cultivars were performed; however, some discrepancy might appear compared to paternity analyses when mother trees have a free choice among different pollen sources from cultivars growing in their surroundings.

The Monumental Olive Trees as Biocultural Heritage of Mediterranean Landscapes: The Case Study of Sicily

Monumental olive trees, with their longevity and their remarkable size, represent an important information source for the comprehension of the territory where they grow and the human societies that have kept them through time. Across the centuries, olive trees are the only cultivated plants that tell the story of Mediterranean landscapes. The same as stone monuments, these green monuments represent a real Mediterranean natural and cultural heritage. The aim of this paper is to discuss the value of monumental trees as “biocultural heritage” elements and the role they play in the interpretation of the historical stratification of the landscape. We present the results of a survey of the most significant olive trees growing in Sicily. The selection was based on the “monumentality” aspects of trees, taking into account dendrometric parameters and environmental contexts. The collected dataset constitutes a heterogeneous sample of 367 specimens of considerable size that, in some cases, reach a circumference of about 19 m. Starting from the data presented here, the whole Sicilian territory shows a historical relationship between human and olive. The presence of these plant monuments is, therefore, evidence of long-term, often centennial, landscapes as a result of sustainable use of the territory.

Diallelic self-incompatibility is the main determinant of fertilization patterns in olive orchards

Self-incompatibility (SI) in flowering plants potentially represents a major obstacle for sexual reproduction, especially when the number of S-alleles is low. The situation is extreme in the commercially important olive tree, where in vitro pollination assays suggested the existence of a diallelic SI (DSI) system involving only two groups (G1 and G2). Varieties belonging to the same SI group cannot fertilize each other, such that successful fruit production is predicted to require pollination between varieties of different groups. To test this prediction, we explored the extent to which the DSI system determines fertilization patterns under field conditions. One hundred and seventeen olive cultivars were first genotyped using 10 highly polymorphic dinucleotide Simple Sequence Repeat (SSR) markers to ascertain varietal identity. Cultivars were then phenotyped through controlled pollination tests to assign each of them to one of the two SI groups. We then collected and genotyped 1440 open pollinated embryos from five different orchards constituted of seven local cultivars with known group of incompatibility groups. Embryos genotype information were used: (i) to assign embryos to the most likely pollen donor genotype in the neighbourhood using paternity analysis, and (ii) to compare the composition of the pollen cloud genetic among recipient trees in the five sites. The paternity analysis showed that the DSI system is the main determinant of fertilization success under field open pollination conditions: G1 cultivars sired seeds exclusively on G2 cultivars, and reciprocally. No self-fertilization events were observed. Our results demonstrate that DSI is a potent force determining pollination success among varieties within olive orchards used for production. They have the potential to improve management practices by guiding the selection of compatible varieties to avoid planting orchards containing sets of varieties with strongly unbalanced SI groups, as these would lead to suboptimal olive production.