Who’s Your Daddy: Family Tree and Future of the Species Edition

In all of my previous “Who’s Your Daddy” posts, I examined the parentage of one individual grape.  Today’s “Who’s Your Daddy” is a bit different in that I’ll be discussing the parentage of, well, all grapes (specifically, all those that are in the USDA grape germplasm collection).

 

Research has found that grape domestication happened in the Near East about 6,000 to 8,000 years old, originating in South Caucasus between the Caspian and Black Seas.  There are thought to be over 10,000 varieties of grapes throughout the world today, which appear to have a relatively high level of genetic

Photo by John Reinhard Weguelin [Public domain], via Wikimedia Commons

Photo by John Reinhard Weguelin [Public domain], via Wikimedia Commons

diversity compared to other organisms.  Genetic diversity is important for several reasons, one of which is the ability to selectively develop genetic strains that are resistant to pathogens.  Problems can arise when there’s too much selection for one particular lineage, decreasing genetic diversity and increasing the

chance of widespread crop loss should a new pathogen rips through the nonresistant population.  Maintaining different lines of genetic diversity is crucial to avoiding total crop loss..

The United States Department of Agriculture (USDA) has a “grape germplasm collection”, which is a collection of grape seeds of ample genetic diversity to help replace plants when they are exposed to new pathogens of which they have no resistance.  Out of the thousands of varieties of grapes, the USDA maintains a library of 950 vinifera germplasms.  Of these, 58% of are clones of at least 1 other germplasm, with 583 of them unique cultivars.

One fascinating thing about grape breeding is that since it’s a vegetatively propagated outcrossing perennial species, ancient cultivars spanning back thousands of years can still coexist with modern cultivars.   Despite the potential for great genetic diversity, relatedness between cultivars remains relatively

Population bottleneck:  Imagine the red line is when a small number of Vinifera grapes were moved from France to North America.  What happens is that the genetic diversity drops significantly due to the drastically reduced population size in the new region.  Then, eventually propagation occurs in the new region, though may not recover to the same level of genetic diversity as the original population due to the lower population numbers to start. Photo by TedE [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/), GFDL (http://www.gnu.org/copyleft/fdl.html) or GFDL (http://www.gnu.org/copyleft/fdl.html)], from Wikimedia Commons

Population bottleneck: Imagine the red line is when a small number of Vinifera grapes were moved from France to North America. What happens is that the genetic diversity drops significantly due to the drastically reduced population size in the new region. Then, eventually propagation occurs in the new region, though may not recover to the same level of genetic diversity as the original population due to the lower population numbers to start.
Photo by TedE [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/), GFDL (http://www.gnu.org/copyleft/fdl.html) or GFDL (http://www.gnu.org/copyleft/fdl.html)], from Wikimedia Commons

close.  In the USDA collection, 74.8% of the cultivars are directly related to at least one other in the collection. In terms of relatedness between cultivar types, 89.3% of relationships connected table grapes to other table grapes, and similarly wine grapes to other wine grapes.  Interestingly, only 6.1% of the connections were between eastern and western grape cultivars, indicating a strong separation (like an ocean?) at one point in history.

From these direct relationships, 47.6% were calculated to be parent-offspring relationships, while the other 52.4% were calculated to be siblings or some equivalent.   Analysis also confirmed a probable Near-East origin of the domesticated grape, with all vinifera cultivars being more closely related to Eastern sylvestris cultivars than Western sylvestris cultivars (sylvestris = wild grapes).  Also, genetic diversity in the Western vinifera cultivars was found to be less genetically diverse than Eastern vinifera cultivars, suggesting some sort of population bottleneck, which can occur in extreme climate changes, human activities, or geographical isolation. After this bottleneck, it seems to be that propagation of different cultivars remained relatively low in the West, thus keeping the numbers of unique cultivars lower than they were in the East where their propagation practices were more complex.

The analysis of the USDA collection indicates that the interrelatedness between different vinifera grape cultivars is extremely close, and that overall the percentage of possible genetic variants in the population is very low.  In order to adjust to a changing climate with unknown roadblocks ahead, it may be crucial to maintain greater genetic diversity of wine grapes so as to avoid possible total wipe-outs of entire cultivars.

Figure 3 from Myles et al (2011) showing the first-degree (direct) relationships among grape cultivars in the USDA collection.  Solid lines represent parent-offspring relationships, while dotted lines represent sibling or equivalent relationships.

Figure 3 from Myles et al (2011) showing the first-degree (direct) relationships among grape cultivars in the USDA collection. Solid lines represent parent-offspring relationships, while dotted lines represent sibling or equivalent relationships.

In a way, we’ve already been warned about the consequences of such a disaster.  Just look at the 19th century Phylloxera crisis. Vineyards all over the globe had been nearly eliminated by the invasive pest known as Phylloxera.  Since they all were so tightly interrelated, not a single cultivar had the genetic makeup necessary to provide resistance against the pest.  In fact, only a small number of native grapevines from North America were resistant against the pest.  Had there been greater genetic diversity in the wine grapes, some cultivars may have survived and could have kept the industry going without having to search the globe for alternatives.  If we want to avoid another crisis that could potentially wipe out the entire wine industry, we need to plan ahead and start increasing genetic diversity of the wine grape.

With a changing climate, some grape cultivars will probably not survive. Developing more genetically diverse cultivars from the current stock may allow the wine industry to have a better chance at success regardless of what Mother Nature throws in the way.  We are already seeing some progress in this area, particularly with the Grape Genetics Research Unit in the Finger Lakes region of New York in the USA, though much more needs to be done.  I’m encouraged by the work that has been done so far, and only hope this type of work continues and becomes more mainstream in wine industries around the globe.

 

Source: Myles, S., Boyko, A.R., Owens, C.L., Brown, P.J., Grassi, F., Aradhya, M.K., Prins, B., Reynolds, A., Chia-J.M., Ware, D., Bustamante, C.D., and Buckler, E.S. 2011. Genetic structure and domestication history of the grape. Proceedings of the National Academy of Sciences 108(9): 3530-3535.

1 comment for “Who’s Your Daddy: Family Tree and Future of the Species Edition

  1. Bob Henry
    October 22, 2013 at 1:45 am

    ON THE SUBJECT OF THE HISTORICAL ROOTS OF WINEMAKING . . .

    From the Los Angeles Times (Section Unknown)
    (January 11, 2011, Page Unknown):

    “Ancient winery found in Armenia;
    The 6,000-year-old winery in a cave in Armenia had all the necessary equipment, including a grape press, fermentation vats and storage jars. A UCLA-led research team believes the site produced wine for religious ceremonies associated with burials.”

    Link: http://articles.latimes.com/2011/jan/11/science/la-sci-ancient-winery-20110111

    By Thomas H. Maugh II
    Times Staff Writer

    A UCLA-led team reported Monday that it had discovered a 6,000-year-old facility in an Armenian cave that contained everything necessary to produce wine from grapes, including a grape press, fermentation vats, storage jars, wine-soaked pottery shards and even a cup and drinking bowl.

    The ancient winery is at least 1,000 years older than any similar installation previously known, and it was found in the same cave where researchers in June announced the discovery of the world’s oldest leather shoe.

    The cave was abandoned when the roof caved in. All the organic material was preserved by a concrete-like layer of sheep dung that sealed everything in and prevented fungi from destroying the remains.

    “Because of this unique preservation, we find all of these previously unknown but imagined organic materials” from the Copper Age, including grape seeds, withered grape vines and remains of pressed grapes, said archaeologist Gregory Areshian of UCLA’s Cotsen Institute of Archaeology, the co-leader of the expedition. Details of the find were described in the January issue of the Journal of Archaeological Science.

    The wine press measured about 3 by 3 1/2 feet and was positioned to drain into a deep vat more than 2 feet deep. Similar to presses utilized as recently as the 19th century throughout Europe and in California, it was clearly meant to be used to smash the grape by foot. All around the top of the press, researchers found handfuls of grape seeds, remains of pressed grapes, grape must and desiccated vines. Botanists determined the species to be Vitis vinifera, the domesticated variety still used to make wine.

    The vat would have held 14 to 15 gallons and was covered by a dark gray residue that contained the plant pigment malvidin, which gives wine its red color and stains clothing and carpets.

    “The site is very important because it is so early and shows how advanced they already were,” said biomolecular archaeologist Patrick McGovern of the University of Pennsylvania, who was not involved in the research. “The fact that winemaking was already so well developed in 4000 BC suggests that the technology probably goes back much earlier.”

    The cave is in a canyon where the Lesser Caucasus Mountains approach the northern end of the Zagros mountain range, near Armenia’s southern border with Iran. Researchers do not yet know the identity of the people who lived in the region, but they clearly carried out extensive trade. Pottery shards from the cave came from as far away as central Iran and southern Asia, and most of the stone implements were made of obsidian from a source that was at least three days away on foot, even though a flint source was much nearer.

    The oldest previously known evidence of wine dates to about 5400 BC and was discovered at a site called Hajji Firuz in the northern Zagros mountains, where McGovern has found jars with traces of tartaric acid crystals, a chemical marker for wine. The oldest previous evidence of grape seeds and other organic materials dates to around 3150 BC and was found in the tomb of the Egyptian king Scorpion I. The oldest wine press is much younger, found in the West Bank and dating to about 1650 BC.

    Areshian said the team originally thought the cave was a habitat, but excavation over the summer indicated that it was a burial site. They now believe that production of wine in the cave was solely for religious ceremonies associated with burials and with honoring the dead.

    “This wine wasn’t used to unwind at the end of the day,” Areshian said. For that, they probably had separate winemaking facilities outside the cave.

    The research was sponsored by UCLA and the National Geographic Society.

    [Write to thomas.maugh@latimes.com]

    — AND SEE THIS —

    From the Los Angeles Times “Main News” Section
    (Saturday, December 11, 2004, Page A28):

    “Hints of 9,000-Year-Old Wine is Unearthed in China”

    Link: http://articles.latimes.com/2004/dec/11/science/sci-wine11

    From Reuters News Service

    Neolithic people in China may have been the first in the world to make wine, according to scientists who have found the earliest evidence of winemaking from pottery shards dating from 7000 BC in northern China.

    Previously, the oldest evidence of fermented beverages dated from 5400 BC and was found at the Neolithic site of Hajji Firuz Tepe in Iran.

    But in a study published this week in the Proceedings of the National Academy of Sciences, Patrick McGovern of the University of Pennsylvania said laboratory tests on pottery jars from the village of Jiahu in Henan province had shown traces of a mixed fermented drink of rice, honey and either grapes or hawthorn fruit.

    “This evidence appears to suggest that the Chinese developed fermented beverages even earlier than the Middle East, or perhaps at the same time,” McGovern told Reuters. “Maybe there were some indirect ties between the Middle East and Central Asia at that time in ancient civilization.”

    McGovern, a molecular archeologist at the university’s Museum of Archaelogy and Anthropology, also analyzed samples of 3,000-year-old wine from hermetically sealed bronze vessels found in Shang Dynasty burial tombs from the Yellow River Basin.

    The liquid was preserved because a thin layer of rust had sealed the bronze jars, he said.

    A small sample of the remains of the wine, a clear colorless liquid, gave off a faint aroma similar to nail polish remover or varnish. McGovern said when he first smelled the wine it was floral scented.

    One of the ancient jars contained a liquid that had traces of wormwood, suggesting the beverage might have been an early version of absinthe.

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