Evolution and Domestication of Wine Grape
The Eurasian grapevine (Vitis vinifera) is a perennial crop belongs to the family Vitaceae, is the most ancient, economically important horticultural crop and cultivated in larger areas in the different parts of the world for fruit, juice and mainly for wine. The family Vitaceae comprises of about 60 inter-fertile species, of which Vitis vinifera is the only species indigenous to Eurasia, which is cultivated extensively for wine production and remaining species are exclusively spread in temperate to warm climatic zones of the Northern hemisphere (Soejima and Wen 2006) other species include V. riparia, V. rupestris, V. berlandieri. Based on morphological differences Vitis vinifera subdivided into most cultivated V. vinifera ssp vinifera and wild form V. vinifera ssp sylvestris. Approximately 6000 to 10000 BP grape was domesticated in Neolithic Southeast Asia, which is derived from its wild progenitor species (V. vinifera ssp sylvestris). Grapevine cultivation and domestication appear to taken place in a geographical area between the Black Sea and Iran between the seventh and fourth millennia BP (Zohary and Hopf, 2000). The cultivated forms from this geographical area might have evolved and distributed to Near East, Middle East, and Central Europe (Garcia et al., 2006). Several genetic studies showed presence high level genetic diversity in domesticated grape cultivars in Western Europe and North east, by suggesting Spain, Italy and France as secondary domestication centers (Garcia et al., 2006). Later V. vinifera cultivars underwent introgression from local wild garpe cultivars (Myles et al., 2011). First evidence for possible secondary centre origin was given by Grassia et al. (2003) due to presence of several wild garpe accessions in Sardinia (Italy). This evidence was confirmed by Ucchesu et al. (2014) studies on morphological comparision of modern wild seeds and archaeological seeds. Disclosure of large number of grape pips at Sa Osa site dating from middle and late bronze age (1286-1115 Cal BC) allowed them to investigate Sardinia as secondary domestication centre for grape.
Several dramatic changes might have happened during domestication process of the biology of grapes to ensure the greater yield, customary production and desired sugar content for better fermentation (Pouget, 1988). The major changes occurred during the domestication process, includes changes in bunch and berry size, increased variation in berry color and dioecious to hermaphrodite nature. Hermaphoditism considered as one of the important peculiarity of present cultivated grape, which is probably due to genetic modification as a result of domestication process (Zecca et al., 2010; Zohary et al., 2012). Seed morphology studies of different Vitis species revealed that domestication of grape probably began with Eurasian wild grape (V. sylvestris) in Southeast Asia and southern Armenia and Georgia (Gyulai et al. 2009). It is uncertain whether these changes are happened due to human selection or mutations or sexual crosses or by vegetative propagation methods. And this uncertainty persists over period and place of domestication. The archeological records revealed that domestication of cultivated grapes (V. vinifera ssp vinifera) which are found more closely related to their wild progenitor (V. vinifera ssp sylvestris) from North East region which confirms the earlier evidence of the origin of vinifera in the North East. The wild progenitor seeds (about 3mm long) were collected from Turkish city of Urfa and also first reliable evidence of grape cultivation was uncovered in Turkey at Kurban Hoyuk (Gyulai et al., 2009). Myles et al. (2011) studied over 1000 samples of cultivated and wild grapes from the USDA grape collections in New York, Geneva, Davis, and California to explore the history of grape domestication using thousands of molecular markers. Wild grapevine genetic diversity and relationship among wild and cultivated grape accessions were carried out using 22 nuclear and three chloroplast microsatellite loci. This study showed clear difference between 21 wild and 13 cultivated grape accessions in Turkish germplasm by providing basis for future phylogenetic relationship studies in the Vitis genus (Karatas et al., 2014). This et al (2006) discussed archaeological and historical evidence of primo-domestication of grape in Near-East region and also the presence of wild grape forms in different places of Europe during the Neolithic period in his detailed review on historical origin and genetic diversity of wine grapes. They also reported first convincing evidence of seeds of domesticated grapes dated from nearly 8000 BP was excavated in Georgia and turkey. The same kind of study on archeological and historical data, Terral et al., (2010) analyzed seed shape characterization of cultivated varieties such as ‘Claritte and Mondeuseblanche’ and well preserved archeological seeds to provide accurate information about wild and cultivated grapes and their relation to domestication process. They suggest that the Languedoc region might constituted as a domestication center. Based on recent archaeological written sources demonstrated the cultivation of Grape in Southern France is dated back 600 BCE and also excavations made over larger areas of South-Eastern France clearly depicted the spread of viticulture during that period (Brun, 2011). Another archaeobotanical records showed usage of wild grapes for wine production as well as table purpose during Neolithic in European context (Zohary et al., 2012). Strong evidence for wine production was discovered from archaeological excavations from Areni-1 cave complex in Southeastern Armenia around 4000 BCE in the late Chalcolithic period (Barnard et al., 2011). Evidences for ancient wine making and viticulture were unearthed in old kingdom tombs, Egypt. Also, different archaeobotany and genetics studies treated grapevine domestication as a most complex, slow, and progressive procedure. Interestingly Bouby et al (2013) revealed grape primary domestication facts in Southwest Asia and hypothesized slow domestication process probably related to the role of sexual reproduction, which is more important than other facts.
Dissemination of the domesticated wine grape lines
Modern cultivars of grape derived from its progenitor species (Vitis vinifera ssp sylvestris) as a result of the domestication. Wild progenitor species is a woody climber bears black skinned berries with unpigmented flesh and grows in riverside basins and distributed widely from Western Europe to the Trans-Caucasian Zone except for the most southern mediterranean region (Arnold et al 1998). Especially Vitis genus comprises of more than 70 species, these species were originated at different places all over the world includes Asia Minor, East Asia, South Europe, North and Central America (Wang et al., 2008). Grape cultivation started spreading from its initial domesticated regions such as Jordan valley during 3000-3500 BC to other parts of the world includes northern, eastern and western parts of Eurasia to Northern Africa (De Candolle, 1886). Later these grapes were introduced into new world countries (America) starting from the 16th century by European colonists, as a seed followed by cuttings from their primary originated places (East Europe, Italy, France, Germany, Spain). During the 19th century, cultivars were spread to South America, Australia, and New Zealand further to North Africa (Royer, 1988). Likewise, grape species spread from traditional temperate growing regions to non-traditional tropical regions such India, Thailand, Brazil, and Venezuela etc for the different purposes such as fruit, juice and wine production. Drastic reduction in genetic diversity for both wild and cultivated grapes recorded in Europe during the 19th century because of the widespread of diseases (Phylloxera, mildews) from North America and as well as human impact on their natural habitats. Later many North American and Asian, naturally occurring wild Vitis species showed resistance/tolerance against many biotic and abiotic stresses (Wan et al., 2008). An evolutionary genomic study on grape domestication was carried out using pulled genomic data, which showed presence of more deleterious genes (5.2%) in cultivated forms as compared to wild forms without much affect on their fitness (Gauti et al., 2017). Genetic diversity studies using 950 vinifera and 59 sylvestris accessions by a chip containing 9000 SNPs (simple sequence repeats) (Myles et al., 2011) showed considerable reduction in species diversity. Wine grape color associates with allelic variation in the domestication gene VvmybA1 studies provided strong evidence for evolution of grapes after domestication process and its impact on modification of fruit and wine quality. Especially the cultivated grapevine cultivars faced drastic reduction in genetic diversity over the last 50 years, on account of globalization of wine markets and companies, which led to development of new cultivars for wine production as well as table purpose such as Chardonnay, Cabernet Sauvignon, Syrah, and Merlot and disappearance of old local cultivars and landraces (This et al., 2006). Zecca et al. (2012) published first study on molecular phylogeny of the genus Vitis mainly based nuclear and chloroplast sequences to reconstruct the evolutionary history of grapes, the results showed the fascinating facts about speciation process of grapes which probably result from both historical geography and paleoclimatic forces and also found primary disjunction between old world and new world grape species.