{"id":232,"date":"2011-07-24T20:12:02","date_gmt":"2011-07-24T19:12:02","guid":{"rendered":"http:\/\/www.northeastwine.org.uk\/Blog\/?p=232"},"modified":"2012-06-09T20:25:44","modified_gmt":"2012-06-09T19:25:44","slug":"grapevine-dna-the-genetics-of-wine","status":"publish","type":"post","link":"https:\/\/www.northeastwine.org.uk\/Blog\/grapevine-dna-the-genetics-of-wine\/","title":{"rendered":"Grapevine DNA – The genetics of wine"},"content":{"rendered":"
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At first glance Genetics may seem a strange topic for a Wine Blog, but look closer and you\u2019ll discover that humans have been genetically modifying the grapevine ever since it was first farmed over 6,000 years ago by selecting the best growths and characteristics (results of genetic variation and mutation) and then locking them in by vegetative propagation (aka cloning)<\/strong><\/a><\/em>. As we progress into the 21st<\/sup> Century advances in molecular genetics allow us to look deep into the DNA of this intoxicating plant to uncover its history and potentially allow further manipulation of its future.\u00a0\"\"<\/a><\/strong> <\/em><\/em><\/p>\n

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<\/em>First some background Biology. There are over 60 distinct species of fruit producing vines of the Genus Vitis<\/em><\/a>, in the Family Vitaceae,<\/em> but, with a few rare exceptions (such as the Norton grape<\/a>) there is only one that attracts the attention of you and I, the Eurasian vine Vitis vinifera<\/em> L. used in the production of table grapes, raisins and wine which has spread around the world with human agriculture (the L. shows that this was one of the original plant species named by the founding father of biological classification – Carl Linnaeus<\/a> in his Species plantarum<\/em> in 1753).<\/p>\n

Genetic research by scientists in Australia<\/a> show that originally all grape varieties were red, but several thousand years ago two independent genes involved in skin colour mutated at about the same time to produce the first pale fruit, the ancestor of today\u2019s white varieties. The earliest known white wine<\/a> has been confirmed from the time of Tutankhamun, more than 3300 years ago.<\/p>\n

Most members of the Vitis <\/em>species, and all V.<\/em> vinifera<\/em>, have 19 pairs of chromosomes; 38 units of hereditary that carry the DNA within each cell and on into the next generation. Research has shown that V. vinifera<\/em> has approximately 30,000 genes spread over 500Mb of DNA (Mb = Megabase pairs, a unit of DNA length). Compare this to humans, who have 23 pairs of chromosomes containing 3300 Mb of DNA carrying..\u2026 30,000 <\/strong>genes. Yes, as a species we have no more genes that a grapevine, just a lot more junk DNA in between them!<\/p>\n

The majority of Vitis<\/em> are dioecious<\/a>, separate plants are either male or female and cannot pollinate themselves, while V. vinifera<\/em> are hermaphrodes and can self-fertilise (the Norton variety mentioned above is referenced as V. aestivalis<\/em>, but the fact that it can self-fertilise suggests more than a touch of V. vinifera<\/em> in its parentage). Rather than let nature take its course modern viticulture is based on using cuttings (cultivars) to produce clones of the original plant to preserve their desirable characteristics, such as fruit quality. There could be up to 10,000 cultivars of V. vinifera<\/em> in existence (about 7000 red and 3000 white varieties) and these are the names we see on the labels of our favourite wines; Cabernet, Syrah, Riesling, Verdejo, Assyrtiko etc. In trying to visualise the varieties genetically I liked the description found on <\/em>\u201cProfessional friends of wine<\/a><\/strong>\u201d \u00a0likening them to human populations \u201ceach variety should be considered a “surname” <\/em>which can have its own close family and extended relations stretching back in time, but which may have different names or marriages into other families\u201d. <\/em>\u00a0<\/em><\/p>\n

\"\"<\/a>In their 2006 paper<\/a> Vouillamoz & Grando of the Istituto Agrario di San Michele all’Adige discussed a key aspect of cloning; namely that it was difficult, often impossible, to know the family history of a single cultivar – genetically it may be tens, hundreds or even thousands of years old.<\/p>\n

While leaf morphology was used to guess relationships in the past now molecular genetic techniques allow for more precise identification of related varieties of V.<\/em> vinifera<\/em>. Similar to the 1997 finding at UCDavis<\/a> that Cabernet Sauvignon is the offspring of Cabernet Franc and Sauvignon Blanc they showed that Pinot Noir, \u201cone of the most ancient western European cultivars still in cultivation today\u201d<\/em>\u00a0 is related to Syrah (either a \u201cgreat-grandfather, great-uncle or cousin<\/em>\u201d). Unfortunately they also pointed out that getting a complete family tree of the major varieties is not realistic as many of the contributory family members will likely be extinct, something just avoided with Gouais Blanc, the almost defunct white variety which, along with Pinot, was involved in the parentage of grapes such as Chardonnay and Gamay.
\nNevertheless a glimpse of this family tree was presented in January 2011 in New Scientist magazine<\/a> from a study by Sean Myles of Stanford University.\"\"<\/a><\/p>\n

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<\/em>Cloning of our favourite varieties is not the only genetic dabbling done in the name of viticulture, how about hybrids<\/a> and chimeras<\/a>? \u00a0The devastation of European vineyards by Phylloxera in the 19th<\/sup> century led to the widespread grafting<\/a> of old world V. vinifera <\/em>onto the rootstock of native American species such as V. aestivalis,<\/em> \u00a0V. riparia, V. rupestris, V. champinii, V. candicans<\/em> etc. (or on crossings of these with V. vinifera<\/em>).
\nLet\u2019s just be clear here, the grafting of components of one distinct species onto another separate species or a hybrid cross of mixed species – that is genetic modification of the highest level, and something done in agriculture for hundreds of years, not just with grapevines. Of course all of this is done primarily for disease resistance and maintaining plant and fruit characteristics.<\/p>\n

Like many plants V. vinifera<\/em> is highly heterozygous, meaning that for its 19 pairs of chromosomes the 2 members of each pair (the homologues) show a large degree of DNA variation when compared to each other. This was highlighted in the 2007 mapping of the Pinot Noir genome by Riccardo Velasco & colleagues, also of the Istituto Agrario di of San Michele all’Adige. Their findings<\/a> showed that, on average, there was an 11.2% variation between each of the 19 sets of homologues, which is an enormous amount. As both of Pinot Noir\u2019s parents provided one of every homologue this shows how different, genetically, those parent varieties were, and by assumption all V. vinifera<\/em> varieties – that level of variation is greater than across all the members of the great ape families; Orangutans, Chimpanzees, Bonobos, Gorillas and, of course, Humans. This also explains why vegetative propagation of grapevines is a necessity, since V. vinifera<\/em> does not seem to tolerate any degree of inbreeding and in normal sexual reproduction actively mixes up the DNA it passes onto the next generation, which would create chaos for viticulturists trying to maintain favourite features. I wish the adventurous Randall Grahm luck with his recently announced plan to grow a vineyard entirely from seedlings<\/a>, given the recombination data above each new plant is likely to be radically different to its parents!<\/p>\n

Velasco\u2019s paper is the grape equivalent to the Human Genome project<\/a> and is a fascinating, if somewhat technical, read showing how genes for disease resistance make up a large proportion of the genome. But if this is so why are commercial varieties so vulnerable to disease while wild grape varieties typically exhibit significantly more disease resistance?
\nWild vines reproduce sexually and resistance evolves competitively with the diseases and vectors they\u2019re exposed to \u2013 think of it as allowing their genes to download the latest Operating System updates and Anti-Virus software. Unfortunately, because of long-term cloning, the Pinots, Cabernets etc have had their automatic updates disabled and are no longer able to counter any new pathogens the vine is exposed to. Of course you could cross wild and cultivated varieties to breed in the new resistance, but this would also affect the grape characteristics you want to keep.<\/p>\n

Velasco suggests the research could lead to new \u201cmolecular breeding\u201d programs, where clusters of resistance genes from wild strain vines could be selectively crossed into the domesticated\u00a0 varieties without losing the genes involved in grape or wine quality.This was the premise of the planting of a GMO Vineyard in France (Steve Savage summarised the plan concisely in his 2010 blog post<\/a>), unfortunately in a Luddite incident barely a month later the vines were destroyed by protestors<\/a>.<\/p>\n

It\u2019s not just the vine itself that is now open to genetic changes, there\u2019s another species involved in winemaking \u2013 Yeast. There are already new strains of these single cell organisms that can tolerate higher alcohol levels than ever before<\/a>, perfect for the \u201cNo Wimpy Wines\u201d generation and others designed to finish at lower levels to counter these Frankenwines, but that would be the start of a whole new controversy, so I\u2019ll bring this article to an end with Dennis Gray of the University of Florida, who has been working with Muscadine grapes<\/a> for many years. \"\"<\/a>
\nIn The Economist review<\/a><\/strong> of the Pinot Noir sequencing Gray was mentioned as having started field trials of genetically engineered grapes against Pierce\u2019s Disease<\/a>, a bacterial infection which has been touched upon in an earlier Reign of Terroir post<\/a>. More recently he\u2019s been working<\/a> on fungal disease resistance with Thompson Seedless table grapes the hope of producing disease-resistant varieties of Chenin Blanc able to thrive in Florida’s climate.<\/p>\n

Researching this topic allowed me an intriguing glimpse into aspects of viticulture and winemaking I had not truly appreciated and begs the question, should we be afraid of future genetic tinkering with our favourite beverage? For me, as a trained geneticist, the answer is no; partly because the fermented grape juice that makes it into our glasses doesn\u2019t contain active DNA anyway, but mostly because we\u2019ve been genetically modifying the vine for thousands of years – so why should we stop now?<\/p>\n

Greybeard <\/strong><\/p>\n

(Based on, and updated from, an original article published March 3rd, 2008, on Reign of Terroir<\/a><\/em><\/strong>)
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Additional reading from Science Daily<\/strong>:<\/em>
\nBringing Better Grapes a Step Closer to Reality<\/a>
\nPinot Noir Grape Sequenced
\nRipening Secrets Of The Vine Revealed<\/a><\/p>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

At first glance Genetics may seem a strange topic for a Wine Blog, but look closer and you\u2019ll discover that humans have been genetically modifying the grapevine ever since it was first farmed over 6,000 years ago by selecting the … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":236,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"footnotes":""},"categories":[52],"tags":[53,54,55],"_links":{"self":[{"href":"https:\/\/www.northeastwine.org.uk\/Blog\/wp-json\/wp\/v2\/posts\/232"}],"collection":[{"href":"https:\/\/www.northeastwine.org.uk\/Blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.northeastwine.org.uk\/Blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.northeastwine.org.uk\/Blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.northeastwine.org.uk\/Blog\/wp-json\/wp\/v2\/comments?post=232"}],"version-history":[{"count":3,"href":"https:\/\/www.northeastwine.org.uk\/Blog\/wp-json\/wp\/v2\/posts\/232\/revisions"}],"predecessor-version":[{"id":239,"href":"https:\/\/www.northeastwine.org.uk\/Blog\/wp-json\/wp\/v2\/posts\/232\/revisions\/239"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.northeastwine.org.uk\/Blog\/wp-json\/wp\/v2\/media\/236"}],"wp:attachment":[{"href":"https:\/\/www.northeastwine.org.uk\/Blog\/wp-json\/wp\/v2\/media?parent=232"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.northeastwine.org.uk\/Blog\/wp-json\/wp\/v2\/categories?post=232"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.northeastwine.org.uk\/Blog\/wp-json\/wp\/v2\/tags?post=232"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}