There is also the possibility of a loss of accessions occurring during the revival, either due to contamination or low recovery, especially for some specific Vitis varieties. Seed bank storage is also utilized for the ex situ conservation of trees, although the germinating progeny will show segregating genotypes. However, plants with recalcitrant and intermediate seeds cannot stand desiccation conditions and cold storage without losing viability; only orthodox seeds are highly suited to this procedure. Moreover, conservation via storing seeds is suitable only for wild grapevines, and not for cultivated ones. Therefore, field gene bank collections are important for such species. In field gene bank collections, tree species are maintained and multiplied indefinitely, using seeds or vegetative propagation; this emphasizes the importance of having a long-term plan for the sustainability of such collections. However, maintenance of such collections is costly , and extensive maintenance actions are required. Moreover, these collections are vulnerable to climate change, biotic and abiotic stresses, and sometimes natural disasters. The emergence of intense competition in the international wine market has encouraged the idea of recovering high-quality ancient and indigenous accessions. As a result, a large number of indigenous accessions have been collected from wild and old vineyards,procona system and maintained in the field collections of grapevine-growing countries, including Israel, the USA, Spain, Italy, and many other countries. For example, the United States Department of Agriculture—Agricultural Research Service collections of wild grapevines at the Plant Genetic Resource Unit and the National Clonal Germplasm Repository maintain around 5000 accessions as a field collection. The FEM grape germplasm collection at San Michele all’Adige, Italy, maintains 2273 accessions.
The IFAPA research center “Rancho de la Merced” hosts 930 accessions, and the “El Encín” Vine Varieties Collection, Spain, has 966 indigenous accessions. Finally, the Vitis International Variety Catalogue is a database of ~23,000 cultivars, breeding lines, and Vitis species, that provides a comprehensive overview of most international grapevine collections. The grapevine is one of the most sensitive cultivated plants; it is very responsive to its surrounding environment. Different varieties may have a wide range of responses to specific stressors; thus, maintaining a wide range of cultivars in a field collection using a uniform growth protocol is challenging. As mentioned above, grapevine field collections also require large spaces, are labor-intensive, expensive to maintain, and are exposed to natural disasters, climate change, and infection by pathogens. Therefore, the maintenance of field grapevine collections is challenging. In spite of these complications, the importance of maintaining grapevine field collections is growing in light of current and forecasted climate changes; the sustainability of current commercial grapevine varieties is under greater pressure as a result of global warming. New, resistant varieties will be greatly needed, and it is anticipated that the diversity found in germplasm collections will become increasingly valuable for future breeding programs . Genomics-assisted breeding will reduce the time and costs that are required to breed new cultivars that possess desirable traits. The methodical collection of data from a field collection can enhance our understanding of phenological variations, and of individual responses to various biotic and abiotic factors—for instance, in terms of cold hardiness, blooming time, drought stress , as well as important commercial traits such as wine characteristics. Due to the adaptability of such varieties in local microclimatic conditions, these varieties can provide root stocks that are resistant to the salt and drought stresses that are associated with climate change.
Israel is characterized by a dramatic climatic gradient, from the northern moderate temperature and humidity of the Golan Heights, to the southern hot and dry Negev. Here, we describe the advantages of maintaining a unique field indigenous collection in Ariel, Israel. This collection includes 96 accessions that were collected in Israel during the last decade, representing one of the most ancient grape populations in the world, and one that is suspected of having been domesticated from local Vitis sylvestris populations. Furthermore, individual grapevines in this collection were collected from very harsh ecosystems, including the Mediterranean Sea shore, the Negev desert, and dry mountainous areas; such grapevines represent a unique opportunity to study abiotic stress resistances. This collection was used to gain a better understanding of the genomic structure of the domesticated and wild grape populations in the south Levant. This study will argue the benefits of maintaining this unique in-field collection in order to study drought resistance, phenotypic and phenological variations, and grape aroma profiles of previously uncharacterized grape varieties. This study presents the physiological data retrieved from 33 varieties , measured at five time points during a drought stress experiment of 10 weeks. Using k-means analysis to classify the individual vines into groups [using the physiological information measured for each vine at all five time points—stem water potential , photosynthesis, and stomata conductance], we show that the vines, represented by dots, are divided into three groups that are based on their physiological behavior during the extended drought stress period . Next, we annotated every dot to the specific vine and variety, and left in the analysis only those varieties in which all four vines are classified into the same group. When looking into the physiological data for the vines represented in each group—the group of varieties marked by green dots—Nitzan 3 and Beer, which come from a group that is more separated from the other two groups, are varieties that are characterized by the most negative SWP and lowest stomata conductance at the later stages of the experiment . Meanwhile, the group of varieties marked by red dots—Shami and Batar Nitzamin—had improved parameters at the later stages. Finally, the intermediate group marked by the blue dots—Jandaly and Ramtania—showed moderate parameters at the late stages, and had some intermixing with the red group .The correlation between stomata conductance and photosynthetic efficiency of varieties under drought stress shows close to linear relations with high R 2 levels for most varieties.
Nevertheless, the slopes are higher for the stable varieties than for those drought-sensitive varieties that show a more extreme reaction , meaning that the red group transpires more water for the same photosynthetic efficiency. Next, we conducted a correlation between midday stem water potential and stomatal conductance for two representative varieties for each response strategy during all five measuring points . The correlation clearly shows the differences between the groups—the more stable varieties, Shami and Batar-Nitzanim, are only mildly affected by extended drought, reaching only circa -1MPa, and maintaining relatively high gs at the later stages of the experiment, while the sensitive varieties, Beer and Nitzan 3, are dramatically affected at the early stages, reaching more negative levels of SWP and with lower stomatal conductance. The Ramtania and Jandaly varieties represent the moderate group, dropping faster into a more negative SWP and lower gs than the stable group, but not as dramatically as the sensitive varieties.A comprehensive dating of the phenological stages for the accessions in the collection was conducted during the season of 2018. Determination of the phenological sequence is generally important for the characterization of each variety as an early, medium, or late blooming. When extended to the ripening period, it also enables planning for an extended harvest season for table grapes, and enables planning for early or late harvest for wine making purposes. Interestingly,procona valencia buckets when referring to the former division of the varieties by their drought stress reactions, we found that stable varieties show very late bud break and foliage development compared to sensitive varieties. By fruit set, most varieties show a similar development pattern.Studies of phenotypic variation using germplasm collections can improve our understanding of phenotypic plasticity in grapevine varieties, as they respond to changing climatic conditions. Therefore, it is essential to examine diverse germplasms to better understand variation in individual responses to changing conditions, and to identify germplasms that can withstand climatic variations for use in breeding programs. In this paper, we have shown that drought stress, applied uniformly to the whole range of the Israeli germplasm collection which contains six plants for each variety, enables the preliminary identification of drought-stable or drought-sensitive varieties. Stable varieties showed improved SWP and higher levels of stomata conductance under drought stress, while the sensitive varieties dropped in SWP rapidly, as well as in stomata conductance. This initial characterization should be followed by a deeper one, concentrating on the varieties that harbor the most pronounced phenotypes in larger dedicated plots and replications. Using a field germplasm collection for this initial screening has pros and cons. Advantageously, we can count the fact that one can conduct comprehensive surveys that encompass the entire range of varieties, to the trait in hand, and the ease of work, when all varieties are under the same conditions in one plot; this facilitates multiple analyses in a short time. In terms of disadvantages, a collection usually contains a very limited number of vines per variety, with no replicate vines spread in different parts of the vineyards, as we would in stationing a proper field experiment. Thus, when analyzing the plasticity of varieties to traits such as stress resistance, the data collected can serve only as preliminary observations to be verified by wider experiments.
Living germplasm collections can also be valuable resources for characterizing diversity in phenological sequences—bloom time, timing of bud break, and véraison, as well as fruit development, ripening processes, and cold hardiness, when responding to identical sets of environmental conditions on the same site across multiple years and conditions. As we have shown, our tracking of the early phenological sequence in some varieties in our collection is in concert with our findings during the drought stress experiment, and the separation of varieties into “stable” or “sensitive” to drought stress. It seems that the stable varieties are those which are late blooming, while those that are sensitive are early blooming . We suggest that the late bud breaking and foliar development of the “stable” varieties is possibly the mechanism that enables their mild reaction to the initiation of drought stress. The early varieties have around forty additional days to sustain their foliage, possibly causing rapid depletion of the soil water reservoir accumulated during winter. Thus, we suggest that at the point of drought stress initiation , their depleted soil water reservoir leads them into more profound stress, preventing them from keeping their stomata open; meanwhile, the late blooming varieties, which have much larger water reservoirs due to less time sustaining foliage, have improved water status. We will need to continue monitoring both phenological and physiological reactions of the stable and sensitive groups over an extended period of time, in order to understand and validate this suggestion; nevertheless, these surprising observations were possible only through maintaining an in-field collection, with meticulous data collection for different traits. Field germplasm collections can be utilized as reference materials for ampelographic studies. Recent research done at the indigenous grapevine collection at Ariel University revealed information about genetic diversity and single nucleotide polymorphisms among various accessions, which in combination with the ampelographic data collected in field, can enable the definition of varieties and clones. For example, we have previously shown that seed morphology analyses of three sets of SSR identical pairs of varieties—Shami and Tufahi, Karkashani and Zituni, Baluti and Bituni—found that the first two pairs are clearly distinguishable by seed morphology, while the third pair has very similar seed morphology, strengthening this pair’s definition assynonyms. The newly developed method for defining 3D seed morphology joins the more traditional straightforward traits of bunch and berry size and shape, berry color, and taste, which help distinguish synonyms from clones. Indeed, many such variations resulted in the development of popular cultivars such as ‘Pinot gris’ and ‘Pinot blanc’, which are lighter-colored variations of the grapevine cultivar, ‘Pinot noir’, which possesses 17 clones within the USDA grapevine germplasm collection. While such accessions may appear to be genotypic duplicates, especially when a limited number of genetic markers is used to evaluate their differences, they are actually valuable resources for studying plant developmental biology and gene function. Here, we deeply analyzed phenolic composition for some red varieties in the collection, and aroma profiles for the white ones. We show that most red indigenous varieties have relatively low anthocyanin and polyphenolics levels. Only four varieties, namely Marawani, Gilboa, Black Tzuriman, and Baluti, showed higher levels of anthocyanins and phenolic characteristics, which may indicate possible suitability for wine production.