Phylogenetic Relationship Among Wild and Cultivated Grapevine in Sicily: A Hotspot in the Middle of the Mediterranean Basin

Integration of machine learning models with microsatellite markers: New avenue in world grapevine germplasm characterization

Development of efficient analytical techniques is required for effective interpretation of biological data to take novel hypotheses and finding the critical predictive patterns. Machine Learning algorithms provide a novel opportunity for development of low-cost and practical solutions in biology. In this study, we proposed a new integrated analytical approach using supervised machine learning algorithms and microsatellites data of worldwide vitis populations. A total of 1378 wild (V. vinifera spp. sylvestris) and cultivated (V. vinifera spp. sativa) accessions of grapevine were investigated using 20 microsatellite markers. Data cleaning, feature selection, and supervised machine learning classification models vis, Naive Bayes, Support Vector Machine (SVM) and Tree Induction methods were implied to find most indicative and diagnostic alleles to represent wild/cultivated and originated geography of each population. Our combined approaches showed microsatellite markers with the highest differentiating capacity and proved efficiency for our pipeline of classification and prediction of vitis accessions. Moreover, our study proposed the best combination of markers for better distinguishing of populations, which can be exploited in future germplasm conservation and breeding programs.

Genetic relationships and introgression events between wild and cultivated grapevines (Vitis vinifera L.): focus on Italian Lambruscos

Research efforts on genomic structure and ecology of wild populations of Vitis vinifera L. offer insights on grape domestication processes and on the assortment evolution of the cultivated forms. Attention is also paid to the origin of traditional, long-cultivated varieties, often producing renowned and valuable wines. The genetic relationships between 283 Vitis vinifera cultivated varieties (subsp. sativa) and 65 individuals from 9 populations of the sylvestris subspecies mainly from northern Italy were explored by means of molecular markers (27 nuclear and 4 chloroplastic microsatellites). Several episodes of contamination of the wild germplasm by the pollen of specific grape cultivars were detected, implying concern for maintaining the purity of the wild form. At the same time, events of introgression from the wild subspecies resulted playing a crucial role in the emergence of several cultivated varieties with a clear admixed genome ancestry sativa-sylvestris. These included Lambruscos originated from the flat areas crossed by the Po and Adige rivers in northern Italy, while other cultivars still called Lambrusco but typical of hilly areas did not show the same admixed genome. Historical and ecological evidences suggesting an adaptative recent post-domestication process in the origin of several Italian Lambruscos are discussed.

Monitoring and Genotyping of Wild Grapevine (Vitis vinifera L. subsp. sylvestris) in Slovenia

Vitis vinifera L. subsp. sylvestris (sylvestris) is the only native wild grapevine in Eurasia (Europe and western Asia) and is the existing ancestor of the grapevine varieties (for wine and table grape production) belonging to the subsp. sativa. In Slovenia, the prevailing opinion has been that there are no Slovenian sylvestris habitats. This study describes sylvestris in Slovenia for the first time and aims to present an overview of the locations of the wild grapevine in the country. In this project, a sample set of 89 accessions were examined using 24 SSR and 2 SSR markers plus APT3 markers to determine flower sex. The accessions were found in forests on the left bank of the Sava River in Slovenia, on the border between alluvial soils and limestone and dolomite soils, five different sites, some of which are described for the first time. The proportion of female to male accessions differed between sites. At two sites, female plants dominated; at others, the ratio was balanced. The plants' genetic diversity and structure were compared with autochthonous and unique varieties of subsp. sativa from old vineyards in Slovenia and with rootstocks escaped from nature from abandoned vineyards. Sylvestris was clearly distinguishable from vinifera and the rootstocks. Based on genetic analyses, it was confirmed that Slovenian sylvestris is closest to the Balkan and German sylvestris groups. Meanwhile, a safety duplication of the wild grapevine accessions has been established at the University Centre of Viticulture and Enology Meranovo, Faculty of Agriculture and Life Sciences at the University of Maribor.

Genealogical Analyses of 3 Cultivated and 1 Wild Specimen of Vitis vinifera from Greece

Grapevine (Vitis vinifera) has been an important crop with considerable cultural and economic significance for over 2,500 years, and Greece has been an important entry point into Europe for lineages that were domesticated in Western Asia and the Caucasus. However, whole-genome-based investigation of the demographic history of Greek cultivars relative to other European lineages has only started recently. To understand how Greek cultivars relate to Eurasian domesticated and wild populations, we sequenced 3 iconic domesticated strains ('Xinomavro,' 'Agiorgitiko,' 'Mavrotragano') along with 1 wild accession (the vinetree of Pausanias-a historically important wild specimen) and analyzed their genomic diversity together with a large sample of publicly available domesticated and wild strains. We also reconstructed genealogies by leveraging the powerful tsinfer methodology which has not previously been used in this system. We show that cultivated strains from Greece differ genetically from other strains in Europe. Interestingly, all the 3 cultivated Greek strains clustered with cultivated and wild accessions from Transcaucasia, South Asia, and the Levant and are amongst the very few cultivated European strains belonging to this cluster. Furthermore, our results indicate that 'Xinomavro' shares close genealogical proximity with European elite cultivars such as 'Chardonnay,' 'Riesling,' and 'Gamay' but not 'Pinot.' Therefore, the proximity of 'Xinomavro' to Gouais/Heunisch Weiss is confirmed and the utility of ancestral recombination graph reconstruction approaches to study genealogical relationships in crops is highlighted.

Genetic structure of the population of wild-growing vines of the Utrish Nature Reserve

Grapes are one of the most common agricultural crops in the world. Currently, the analysis of genotypes directly at the DNA level is considered to be the most accurate method for studying the plant gene pool. The study of wild vines and ancient varieties in various regions of viticulture is an important direction of research in this field. The purpose of this work was to study the population of wild grapes growing on the territory of the Utrish Nature Reserve on the Black Sea coast of Krasnodar Region. The territory of the reserve is of interest as it is a site of ancient settlements, and the environmental conditions are suitable for the growth of wild grapes. During the survey of the territory, 24 samples of wild grapes were found, which were described according to the main morphological characteristics and analyzed by the molecular genetic method. The found vines were genotyped using 15 DNA markers, including nine commonly used for DNA fingerprinting (VVS2, VVMD5, VVMD7, VVMD25, VVMD27, VVMD28, VVMD32, VrZAG62, VrZAG79) and VVIb23, which allows determining hermaphrodite and dioecious vines. Statistical processing of microsatellite loci polymorphism data was carried out using the GenAlEx 6.5 program. The genetic relationships of the studied vines were evaluated using the PAST 2.17c program. The samples were found to be morphologically and genetically polymorphic. The number of alleles identified in the sample varied from 5 to 18 and averaged 8 alleles per locus. Statistical processing of DNA analysis data made it possible to identify two genetically different populations among the wild discovered vines. An assessment of genetic similarity of the found vines with some local varieties of geographically close viticulture regions, rootstocks and representatives of Vitis sylvestris from other territories was made. One of the populations found in the Utrish Nature Reserve is close to a number of V. sylvestris genotypes, the DNA profiles of which are presented in the Vitis International Variety Catalogue.

Analysis of Wine-Producing Vitis vinifera L. Biotypes, Autochthonous to Crete (Greece), Employing Ampelographic and Microsatellite Markers

Vitis vinifera ssp. vinifera (domesticated grapevine) includes thousands of cultivars, which are classified according to their main uses, as wines, fresh fruits or dried raisins and sultanas since ancient times. Evidence showed that Crete grapevine cultivars and winemaking date back to 2300 BC. In this study, fifty-one genotypes belonging to seven different traditional Vitis vinifera cultivars, presumed autochthonous to the island of Crete, were selected for their wine-producing potential and classified by 51 ampelographic descriptors. In addition, five genotypes belonging to two non-autochthonous cultivars were included as out-group controls. Subsequently, in order to characterize genetic diversity, establish genetic relationships within and between cultivars and solve accession-labeling problems, genotypes were fingerprinted employing Simple Sequence Repeat (SSR or microsatellite) markers. Four of the autochthonous cultivars namely 'Vidiano', 'Vilana', 'Plyto', and 'Moschato Spinas' are used in the local economy for blanc (white) wine production while the rest, namely 'Kotsifali', 'Liatiko' and 'Mantilari' for Noir (red) wines. The two cultivars employed as out-group were 'Moschato Samou' and 'Moschato Alexandrias': both white wine producers. Ampelography-based clustering grouped the majority of genotypes along cultivar-specific clusters. All three Moschato cultivars formed a distinct clade pointing to the non-autochthonous origin of 'Moschato Spinas'. A total of one hundred and thirteen (113) SSR alleles were amplified from thirteen (13) SSR loci, with an average number of alleles per locus equal to 10.23 revealing ample genetic polymorphism. The cumulative probability of identity was also quite high (3.389 × 10^-16). The overall observed heterozygosity was 0.837 while for twenty-nine of the examined genotypes, at least one private SSR allele was detected. The majority of genotypes were grouped in cultivar-specific clusters. The results of this paper pave the way for the certification and registration of clones of some of the most important wine-producing cultivars in Crete.

Pervasive hybridization with local wild relatives in Western European grapevine varieties

Grapevine (Vitis vinifera L.) diversity richness results from a complex domestication history over multiple historical periods. Here, we used whole-genome resequencing to elucidate different aspects of its recent evolutionary history. Our results support a model in which a central domestication event in grapevine was followed by postdomestication hybridization with local wild genotypes, leading to the presence of an introgression signature in modern wine varieties across Western Europe. The strongest signal was associated with a subset of Iberian grapevine varieties showing large introgression tracts. We targeted this study group for further analysis, demonstrating how regions under selection in wild populations from the Iberian Peninsula were preferentially passed on to the cultivated varieties by gene flow. Examination of underlying genes suggests that environmental adaptation played a fundamental role in both the evolution of wild genotypes and the outcome of hybridization with cultivated varieties, supporting a case of adaptive introgression in grapevine.

Autotetraploid Emergence via Somatic Embryogenesis in Vitis vinifera Induces Marked Morphological Changes in Shoots, Mature Leaves, and Stomata

Polyploidy plays an important role in plant adaptation to biotic and abiotic stresses. Alterations of the ploidy in grapevine plants regenerated via somatic embryogenesis (SE) may provide a source of genetic variability useful for the improvement of agronomic characteristics of crops. In the grapevine, the SE induction process may cause ploidy changes without alterations in DNA profile. In the present research, tetraploid plants were observed for 9.3% of ‘Frappato’ grapevine somatic embryos regenerated in medium supplemented with the growth regulators β-naphthoxyacetic acid (10 µM) and N⁶-benzylaminopurine (4.4 µM). Autotetraploid plants regenerated via SE without detectable changes in the DNA profiles were transferred in field conditions to analyze the effect of polyploidization. Different ploidy levels induced several anatomical and morphological changes of the shoots and mature leaves. Alterations have been also observed in stomata. The length and width of stomata of tetraploid leaves were 39.9 and 18.6% higher than diploids, respectively. The chloroplast number per guard cell pair was higher (5.2%) in tetraploid leaves. On the contrary, the stomatal index was markedly decreased (12%) in tetraploid leaves. The observed morphological alterations might be useful traits for breeding of grapevine varieties in a changing environment.

Back to the Origins: Background and Perspectives of Grapevine Domestication

Domestication is a process of selection driven by humans, transforming wild progenitors into domesticated crops. The grapevine (Vitis vinifera L.), besides being one of the most extensively cultivated fruit trees in the world, is also a fascinating subject for evolutionary studies. The domestication process started in the Near East and the varieties obtained were successively spread and cultivated in different areas. Whether the domestication occurred only once, or whether successive domestication events occurred independently, is a highly debated mystery. Moreover, introgression events, breeding and intense trade in the Mediterranean basin have followed, in the last thousands of years, obfuscating the genetic relationships. Although a succession of studies has been carried out to explore grapevine origin and different evolution models are proposed, an overview of the topic remains pending. We review here the findings obtained in the main phylogenetic and genomic studies proposed in the last two decades, to clarify the fundamental questions regarding where, when and how many times grapevine domestication took place. Finally, we argue that the realization of the pan-genome of grapes could be a useful resource to discover and track the changes which have occurred in the genomes and to improve our understanding about the domestication.

Genetic Structure and Relationships among Wild and Cultivated Grapevines from Central Europe and Part of the Western Balkan Peninsula

The genetic diversity and relationship between wild (Vitis vinifera L. subsp. sylvestris (Gmel.) Hegi and cultivated (V. vinifera L. subsp. vinifera) grapevine in the western Balkan region and Central Europe have not been studied together previously, although this area has a rich viticultural past. Here, we studied wild grapevine populations sampled from their natural habitats in several countries of the western Balkan region and Central Europe. Their genetic diversity and structure were compared to cultivars that are traditionally in use in this region. A sample set of 243 accessions was genotyped at 20 nuclear microsatellite loci, including 167 sylvestris and 76 diverse vinifera cultivars. The genetic diversity of the wild grapevines was lower than that of cultivars by all genetic parameters. Both hierarchical and nonhierarchical clustering methods differentiated two main groups, indicating clear separation between wild and cultivated vines but also revealed clear gene flow between the cultivated and wild gene pools through overlaps and admixed ancestry values in the graphs. There was greater affinity to the wild grapes in Central European cultivars than in Balkan cultivars. Fine arrangement of the structure among cultivated grapevines showed differentiation among Central European and Balkan cultivars. These results confirm the divergence of wild grapes from vinifera and highlight the "crossroad" role of the western Balkan peninsula in the broader context of European viticulture.

The Cypriot Indigenous Grapevine Germplasm Is a Multi-Clonal Varietal Mixture

Cypriot vineyards are considered as one among the earliest niches of viticulture and a pivotal hub for the domestication and dissemination of grapevine. The millennial presence of Vitis spp. in this Eastern Mediterranean island has given rise to a plethora of biotypes that have not been adequately characterized, despite their unique attributes and stress tolerance. This ancient germplasm also has an additional value since it survived the phylloxera outbreak; hence, it possesses a large amount of genetic diversity that has been unnoticed. In order to provide useful insights to the lineage of Cypriot vineyards, a two-year-spanning collection of centennial grapevine cultivars mostly regarded to belong to four indigenous variety clusters ("Mavro", "Xynisteri", "Maratheftiko", and "Veriko") was initiated. There were 164 accessions across the broader Commandaria wine zone sampled and characterized using a universal microsatellite primer set. Genetic analysis indicated that considered indigenous Cypriot germplasm has a polyclonal structure with a high level of heterozygosity. Moreover, several lineages or unexplored varieties may exist, since a larger than considered number of discrete genotypes was discovered. Furthermore, it was established that grapevine lineages in Cyprus were shaped across eras via clonal, as well as, sexual propagation. The special attributes of the Cypriot landscape are discussed.

An Updated Checklist of the Sicilian Native Edible Plants: Preserving the Traditional Ecological Knowledge of Century-Old Agro-Pastoral Landscapes

The traditional use of native wild food plants (NWFP) may represent a valuable supplementary food source for the present and future generations. In Sicily, the use of wild plants in the human diet dates back to very ancient times and still plays an important role in some rural communities. Moreover, in this regard, the natural and cultural inheritance of this island is wealthy and diversified for several reasons. First, Sicily hosts a rich vascular flora, with 3,000 native and 350 endemic plants. Second, due to its central position in the Mediterranean, the island has acted as a veritable melting pot for the ethnobotanical knowledge of the rural communities of the entire basin. We reviewed all the available literature and, starting from such omnicomprehensive checklist, partially improved thanks to the data issuing from recent field investigations, we critically revised the whole species list, basing our review on field data issuing from interviews and on our expert knowledge. As a result, we provide a substantially updated list of 292 NWFP growing on the island. Further 34 species, reported as NWFP on previous papers were discarded because they are not native to Sicily, while 45 species were listed separately because their identity, occurrence and local use as food is doubtful and needs to be further investigated. Moreover, we tried to shed light on the ecology (growth form and preferential habitat) of the Sicilian NWFP, with special focus on crop wild relatives (CWR). Our preliminary ecological analyses point out that a high percentage of these plants are linked with the so-called 'cultural' landscapes, patchy semi-natural environments rich in ecotones, leading to the conclusion that the maintenance of century-old agro-pastoral practices may represent an effective way to preserve the local heritage of edible plants. Our study allowed to identify as much as 102 taxa of agronomic interest which could be tested as novel crops in order to face ongoing global changes and to comply with sustainable agriculture policies. Among them, 39 taxa show promising traits in terms of tolerance to one or more environmental stress factors, while 55 more are considered CWR and/or can be easily cultivated and/or show high productivity/yield potential.

Molecular Analysis of the Official Algerian Olive Collection Highlighted a Hotspot of Biodiversity in the Central Mediterranean Basin

Genetic diversity and population structure studies of local olive germplasm are important to safeguard biodiversity, for genetic resources management and to improve the knowledge on the distribution and evolution patterns of this species. In the present study Algerian olive germplasm was characterized using 16 nuclear (nuSSR) and six chloroplast (cpSSR) microsatellites. Algerian varieties, collected from the National Olive Germplasm Repository (ITAFV), 10 of which had never been genotyped before, were analyzed. Our results highlighted the presence of an exclusive genetic core represented by 13 cultivars located in a mountainous area in the North-East of Algeria, named Little Kabylie. Comparison with published datasets, representative of the Mediterranean genetic background, revealed that the most Algerian varieties showed affinity with Central and Eastern Mediterranean cultivars. Interestingly, cpSSR phylogenetic analysis supported results from nuSSRs, highlighting similarities between Algerian germplasm and wild olives from Greece, Italy, Spain and Morocco. This study sheds light on the genetic relationship of Algerian and Mediterranean olive germplasm suggesting possible events of secondary domestication and/or crossing and hybridization across the Mediterranean area. Our findings revealed a distinctive genetic background for cultivars from Little Kabylie and support the increasing awareness that North Africa represents a hotspot of diversity for crop varieties and crop wild relative species.

Water relations of two Sicilian grapevine cultivars in response to potassium availability and drought stress

We investigated the response of two Sicilian grapevine cultivars, Catarratto and Nero d'Avola, to potassium deficiency and drought stress. Two-year-old plants grafted on 1103 Paulsen were grown in agriperlite, with or without potassium in the fertigation solution for six weeks, and subjected to moderate drought stress by suspending irrigation for one week. Potassium content of leaves, roots and xylem sap were measured with an ion-selective electrode. Changes in stomatal conductance, stem and leaf water potential and hydraulic conductance were compared between genotypes and treatments. Potassium deficiency led to significant decreases in leaf potassium content in both cultivars and under both well-watered and drought stress conditions. Potassium content in xylem sap showed no significant differences between cultivars and was correlated with stem hydraulic conductance, particularly in the drought stress treatments. Under drought stress conditions, potassium availability led to an increase in stomatal conductance, particularly in Nero d'Avola. Both cultivars showed a rather isohydric behavior under these experimental conditions, and the level of isohydry varied with potassium availability. These results can be useful for the development of optimal fertigation practices and the selection of drought tolerant varieties.