Genetic Resources for Viticulture

Grapevine (Vitis vinifera L.) is one of the most widely cultivated and economically valuable horticultural crops globally [1]. According to the International Organisation of Vine and Wine (OIV), the world’s vineyard surface stands at 7.2 million hectares [2], distributed mainly between latitudes 4° and 51° in the Northern Hemisphere (NH) and between 6° and 45° in the Southern Hemisphere (SH) [3]. In the last 3 years, there has been a 2.3% decrease in the global vineyard surface area, driven by the removal of vineyards in major vine-growing regions (including all grape types: wine, table, and dried grapes) across both hemispheres.

This reduction was mainly motivated by extreme climatic conditions and widespread fungal diseases that severely impacted many vineyards worldwide, culminating in a historically low global wine production of 237 million hectoliters. This marked a 10% drop from 2022 and represented the lowest output since 1961, and a decrease of 2.6% in the consumption of wine [2]. These numbers show that viticulture is facing new challenges such as climate change, diseases, pests, and the need to produce sustainably, adapting to consumer demand and taste [4,5].

In this context, the genetic resources available for viticulture could be of particular interest. Internationally, there are approximately 253 institutions holding plant material, and 23,000 cultivars are registered according to the Vitis International Varieties Catalogue (VIVC) [6]. This is evidence of high levels of recorded biodiversity, which provide a crucial reservoir of genetic heterogeneity, providing a reservoir of valuable allelic combinations that can offer genetic resistance or tolerance to both biotic and abiotic stresses [7].

In this Special Issue entitled “Genetic Resources for Viticulture”, we would like to include studies related to the identification and agronomic, physiological, and oenological characterization of new and local grapevine varieties, rootstocks, clones, and interspecific hybrids as sources of genetic resources to meet the challenges of viticulture.

1. An Overview of Published Articles

The articles by Fort et al. (2023, 2024) (contributions 1, 2, and 3, respectively) explore the genetic diversity of grapevines (Vitis vinifera L.) cultivated in the Canary volcanic archipelago, located in European overseas territory (near Western Sahara). The origin of the vine in the Canary Islands comes from the introduction of European varieties in the 15th century. These islands are home to a great diversity of vines due to their evolution and adaptation to these habitats. In these studies, the volcanic islands of La Gomera, Fuerteventura, and El Hierro have been prospected, collecting a total of 247 samples of grapevine plants, which were genotyped using 20 SSRs. In addition, a parentage study was carried out with the different genotypes obtained. The results of these research articles revealed notable genetic diversity among Canary Islands strains, suggesting a long history of cultivation and adaptation to island conditions. An outstanding discovery was the identification of local varieties exclusive to each island, representing a valuable genetic heritage. These native varieties could harbor genes for disease resistance, drought tolerance, or unique organoleptic characteristics, making them a genetic resource of great interest for varietal improvement. Likewise, the articles made it possible to trace kinship relationships between the Canary varieties and other varieties from different wine regions, providing information on the origin and dispersion of the vines in the archipelago. The authors concluded these articles by pointing out the importance of the Canary Islands as reservoirs of genetic diversity of the vine. These results can not only contribute to improving knowledge of the history and evolution of viticulture in the archipelago, but also be of great interest for the conservation of this genetic heritage. The identification and characterization of local varieties from the Canary Islands could open up new perspectives of interest in the recovery and valorization of wine heritage, as well as for the creation of new high-quality wines adapted to local conditions.

González et al. (2023) (contribution 4) focused on revealing the rich genetic diversity of vines (Vitis vinifera L.) grown on the islands of Ibiza and Formentera, belonging to the Balearic archipelago (Spain). By combining genetic data with ethnobotanical information, the authors managed to decipher the complex history of these varieties and establish phylogenetic relationships between them. The set of results obtained after the analysis of microsatellite markers and descriptions of morphological and ampelometric characteristics, together with the ethnobotanical study through interviews with local winegrowers to collect information on the cultivated varieties, local names, and their traditional use, revealed a great diversity of genetics between the strains grown on both islands. This suggests a long history of cultivation and selection, as well as an adaptation to the agroclimatic conditions of each island. Through this research, the researchers identified new synonyms and homonyms for some varieties, which could help clarify the nomenclature and avoid confusion in their identification. Likewise, new kinship relationships were established between some varieties, which makes it possible to reconstruct the evolutionary history of viticulture in Ibiza and Formentera. In conclusion, the authors indicated that these findings are not only relevant to the scientific community, but could also be of interest to local viticulture, opening avenues to the recovery of native varieties, in addition to the diversification of the region’s wines.

The research by Rahimi et al. (2023) (contribution 5) systematically described the habitats, growth habits, morphology, and anatomy of widely spread wild grapevine populations growing in two distinct habitats in north Israel (Beit Tsaida and Banias River sites). The results of this work show the identification of plants belonging to Vitis vinifera L. subsp. Sylvestris. These new genetic resources should be conserved for the preservation of the species.

Using morphometric techniques, domestication indices, multivariate analysis, and Bayesian hypothesis testing, Valera et al. (2023) (contribution 6) identify grapevine seeds found in archaeological sites in the ancient Upper Euphrates. Archaeological seeds were compared with a pull of 782 grape seed samples provided by various European and U.S. institutions and entities. Digital imaging techniques and statistical analyses were used to measure various morphological characteristics of the seeds, such as length, width, and thickness. Using Bayesian analysis, statistical models were constructed to compare the archaeological seeds with reference samples of modern and ancient varieties.

In the seventh article, Bhattarai et al. (2023) (contribution 7) focused on characterizing the volatile compound profile of different muscadine grape varieties, a species native to North America with great viticultural potential. To this end, different volatile compounds responsible for the characteristic aromas and flavors were identified and quantified in different varieties of muscadine grapes, as well as in hybrids between muscadine and other vine species. The results showed a diversity of volatile compounds (terpenes, esters, alcohols, ketones, and sulfur compounds) associated with odorant series corresponding to fruity, floral, citrus, green, and spicy odors. In conclusion, this work contributes to a better understanding of the aromatic potential of grapes of this species. The results revealed a significant variation in the composition of aromatic volatile compounds between the different muscadine genotypes studied, as well as distinctive composition patterns depending on the variety and the ripening stage. The results of this study are valuable for muscadine breeding programs, consumer preference studies, and the development of metabolic markers to evaluate the ripening quality of grapes.

The article by Ruiz-García et al. (2023) (contribution 8) focuses on the characterization of new vine varieties obtained from crosses of the Monastrell variety, a red grape native to the region of Murcia, Spain. These new genotypes (“Calblanque”, a white genotype, and “Calnegre”, “Gebas”, and “Myrtia”, red genotypes) have been specifically developed to adapt to the hot and dry climatic conditions of this region and to improve the quality of the wines produced. The red genotypes were selected for their phenolic quality, which was much higher than that of the parents, and for their different harvest dates that allow staggered harvesting and cultivation in different areas. “Calblanque” was selected for its good balance of acidity and aromatic profile. The attributes of these new varieties could allow them to better adapt to the effects of climate change on the quality of grapes and wine in warm areas. Wines made with these new varieties showed greater aromatic complexity and better tannic structure, suggesting great oenological potential. In conclusion, these results indicate that the new varieties obtained from Monastrell crosses represent a valuable tool for wine growers, since they would allow them to adapt to the new environmental conditions generated by climate change in the region of Murcia and produce high-quality wines.

The research works of Rodríguez-Torres et al. (2023) (contribution 9) and Jiménez-Cantizano et al. (2023) (contribution 10) deal with the genetic characterization of local vine varieties, contributing to the preservation and valorization of the wine heritage of Andalusia (Southern Spain). To this end, both articles used microsatellite markers (SSR) for the genetic characterization of the vine and to determine kinship relationships between the different samples.

Rodríguez-Torres et al. (2023) (contribution 9) examined 98 samples from six Andalusian wine-growing areas. To do this, they used microsatellite marker analysis, identifying 33 different genotypes, of which 20 corresponded to varieties already described (11 of them are from six minority cultivars in Andalusia: “Rojal Tinto”, “Beba”, “Zurieles”, “Rome”, “Hebén”, “Mollar Cano”, “Listán Prieto”, “Listán del Condado”, “Jarrosuelto”, “Negra Dorada”, and “Mantúo de Pilas”), while the other 12 profiles did not match previously identified varieties. In addition to the genetic characterization, they carried out a health analysis using an ELISA test to detect the presence of viruses (vine fan virus, vine spot virus, and viruses associated with vine leaf curl) due to the requirement of healthy clones of the new varieties for their authorization for cultivation in Spain.

Meanwhile, Jiménez-Cantizano et al. (2023) (contribution 10) analyzed 49 vine accessions collected in the districts of four provinces of Andalusia (Spain). In total, 30 different genotypes were identified, 22 of which corresponded to known varieties and 8 to new genotypes. These results confirm the high genetic diversity present in local Andalusian varieties. As conclusions of this work, the eight new genotypes identified in this work have not yet been identified and could represent ancient local varieties in danger of extinction. These new cultivars could be used to make original wines and, therefore, these genotypes have been preserved in the “Rancho de la Merced” germplasm bank (Andalusia, Spain). The results of this work show that there is significant biodiversity in old vineyards located in the region of Andalusia of cultivars not yet exploited, which may be of great interest to the wine industry.

The article by Arslan et al. (2023) (contribution 11) focused on analyzing the genetic diversity and population structure of the Kara grape variety, a native variety of Anatolia. To this end, an analysis of 49 Kara grape cultivars from six regional subpopulations in Turkey was carried out, using microsatellite markers (SSR) together with ampelographic characterization. The results of the molecular analyses showed high genetic diversity, possibly explained by the adaptation of the vine to different environmental conditions throughout its history and by selection processes. Four synonyms and five homonymies were also identified. According to the results of the ampelographic analysis, it was determined that the shape of the berry and the density of upright hairs on the young shoot/density of lying hairs at the end of the young shoot were the determining characteristics between the different cultivars. The conclusions of this article indicate that the genetic characterization of the Turkish Kara grape germplasm has been obtained using SSR for the first time. These results could be very useful for the development of other genetic characterization studies of grapes and will contribute to wine research in other areas such as the improvement, protection, and registration of varieties.

In addition to this, this Special Issue includes articles of great interest in the viticulture sector, such as the resistance of the vine against diseases such as Xylella fastidiosa. The article by Martínez et al. (2023) (contribution 12) focuses on evaluating the resistance of different European grapevine cultivars and rootstocks to the bacterium Xylella fastidiosa subsp. fastidiosa, a pathogen that causes serious damage to crops. This research acquires special relevance due to the growing threat that this bacterium poses to viticulture worldwide. Using molecular and phenotypic techniques, the researchers evaluated the plant’s response to infection, analyzing bacterial colonization in different tissues, the expression of genes related to the immune response, and the appearance of symptoms. The results showed a significant difference in resistance to this disease between the different cultivars and rootstocks evaluated. This could allow the identification of varieties and rootstocks that are more tolerant to bacteria, which could be used for the development of more sustainable and effective management strategies.

In parallel, Yin et al. (2023) (contribution 13) have deepened our understanding of the agronomic characteristics of rootstocks, a key aspect for the selection of resistant plant material adapted to different environmental conditions. Rootstocks are vine varieties used as a base for grafting other varieties, and their choice can significantly influence the yield and quality of the vines. For this, characteristics such as the multiplication rate, the time of sprouting and maturation, and vegetative growth were studied, in addition to analyzing the relationship between the vigor of the rootstocks and the inheritance of this trait through the parents, in 31 vine rootstocks. The results revealed wide variability between their ease of propagation and their phenology, suggesting a wide range of adaptations to different environmental conditions. This diversity is crucial for the selection of suitable rootstocks and for optimizing wine production in various regions, allowing the vine to adapt to specific climatic conditions and improving the efficiency of cultivation systems.

2. Conclusions

The vine (Vitis vinifera L.) has been cultivated by humans since ancient times, forming a fundamental pillar of the culture and economy of numerous civilizations. Its wide geographical distribution and its adaptation to diverse climates and soils have given rise to extraordinary genetic diversity. This Special Issue focuses on exploring the genetic diversity of the vine in different wine-growing regions, with a particular emphasis on those territories where viticulture has been an ancient activity in the Mediterranean.

The articles compiled in this volume address various topics, from the genetic characterization of local varieties to the evaluation of disease resistance and adaptation to extreme climatic conditions. Through a combination of molecular, morphological, and statistical analysis, the authors offer a comprehensive view of the genetic complexity of the grapevine and its relationship with environmental and historical factors.

A highlight of this volume is the attention paid to local and indigenous varieties. These varieties, often adapted to specific conditions and carrying a unique genetic heritage, represent an invaluable resource for modern viticulture. The articles presented here reveal the richness and diversity of these varieties, as well as their potential for obtaining high-quality wines and adaptation to the challenges of climate change.

Likewise, this volume highlights the importance of international collaboration in wine research. The articles presented here are the result of the collaboration of researchers from different countries, which has allowed a broader and deeper vision of the genetic diversity of the vine worldwide to be obtained.

In conclusion, this Special Issue offers a valuable contribution to the knowledge of grapevine genetic diversity and its implications for viticulture. The results presented here are relevant from both a scientific and practical perspective and can serve as a basis for future research and applications in the wine sector.

As a final note, we would like to emphasize that this Special Issue is distinguished by its focus on wine regions with a long history of grape cultivation, but which have been less studied compared to other, better-known regions. By exploring the genetic diversity of these regions, this volume can contribute to filling a gap in the scientific literature and offer a new perspective on grapevine evolution and adaptation. Furthermore, the combination of different methodological approaches and the integration of data from various sources make this Special Issue an essential reference for researchers, wine growers, and all those interested in the genetic diversity of the vine and its conservation.