(CN) — Until recently, researchers have hypothesized that cultivated wine grapevine (Vitis vinifera ssp. vinifera) had a single domestication event in Western Asia from its wild progenitor (Vitis vinifera ssp. sylvestris) or that domestication occurred before the advent of agriculture and the cultivation of table grapes.
However, a new study published in Science on Thursday challenges both ideas, indicating there was not one but two domestication events for the cultivation of wine separated during the last glacial advance: one in Western Asia and one in the Caucasus region.
Using chromosomal data from 3,525 cultivated and wild grapevines worldwide — some of which came from previously undocumented specimens in private collections — researchers found that harsh climate conditions during the Pleistocene drove the separation of wild grape ecotypes through habitat fragmentation.
According to lead researcher Yang Dong, it was during this time that ecotypes essentially fragmented into eastern and western subgroups through two bottleneck events, eventually resulting in reduced genetic diversity for western ecotypes — grapevines found in Central Europe and the Iberian Peninsula — by the time of the last glacial maximum 21,000 years ago.
Fast forward to the more habitable climates of the Holocene, about 11,000 years ago, and Dong’s research makes it evident that grapevine domestication occurred simultaneously around the advent of farming to yield table and wine grapevines.
“Despite being separated by over 1000 km, the two domestication processes appear to have occurred contemporaneously with a high degree of shared signatures of selection on the same genes,” wrote Professor Robin Allaby from the University of Warwick in a related perspective for Science.
Notably, Dong’s research also dispels the notion that humans cultivated wine grapevines before table grapes.
“Because [Western Asian table grapevines] and [Caucasian wine grapevines] separately represent table and wine grapevine ancient genetic backgrounds,” wrote Dong. “The dual origin rejects the assumption that wine grapevine predate table grapevines.”
From there, Dong’s research indicates that Western Asia domesticates dispersed into Europe with early farmers, “introgressed” or cross-fertilized with ancient western ecotypes and then diversified along human migration networks into muscat and western wine grape ancestries by the late Neolithic period or 6400–3500 BC.
Also relevant to both oenophiles and fans of molecular biology: Dong and colleagues gained new insight into the specific genes associated with berry palatability, berry skin color and even the floral flavor of muscat grapes.
For instance, while investigating genetic domestication signatures in eastern ecotypes, Dong’s team confirmed previous findings that the selection on flower sexual morphs, berry skin color and berry development all played important roles during grapevine domestication. Yet, Dong’s research also identified shared domestication genes, such as those underlying grapevine growth, physiology, fruit set and resistance to biotic-abiotic stress.
“The enormous dataset produced by Dong et al. will provide insight into the finer points of grape evolution for some time to come,” Allaby wrote within his perspective. “The increased resolution has pinpointed the lightening of berry color to some unknown genes close to the previously implicated MybA locus and has suggested that the ancient muscat flavor is unexpectedly rare possibly because of a pleiotropic constraint that prevents fixation.”
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