Hortus Third offers this definition of a clone: "A plant propagated by asexual or vegetative means, including divisions, buds, cuttings, layers etc...Clone is a horticultural rather than a taxonomic term."
In regards to the grape/wine industry, a clone is a variant of a grape variety that is unique in some detectable way, whether by changes in the way a grapevine expresses a particular gene, or minor mutations in the grape variety. Each clone, in this case let's say a clone of Cabernet sauvignon (CS), will taste like the parent variety, but with slightly varying characteristics, e.g., higher acidity, more concentrated fruit, firmer tannins. Nowadays, it is common practice for growers, and winemakers, to utilise a variety of different clones, much like a cook will select different herbs and spices, to achieve certain flavour profiles in a finished wine.
The fact that I am interested in geeky viticultural goings-on would not come as a surprise to anyone who knows me. But something that surprised me was the scarcity of information available about this particular subject matter. I discovered this (yes, almost two years ago), when I attempted to do some research prior to purchasing some grafted grapevines to fill in the spaces where several vines had died in Vinoland's CS block.
There is a lot of anecdotal information to be had by talking to folks who are interested in viticulture, but a lot of it is useless. Just recently, an acquaintance of Vinomaker mentioned to him that he thought CS clone 169 was a great clone to grow in the Tundra (aka Vinoland, Coombsville AVA). I happen to be familiar with this clone, as Vinomaker used to make wine for a couple we know who used to grow this particular clone. Clone 169 did indeed ripen in a timely fashion in Coombsville. It is a pity we have clone 4 (a veritable retard, in the nicest possible sense of the word) planted here in Vinoland, (and oh, how I wish we didn't). But it is what it is. The little bit of information on clones that is available in written form comes from research conducted by John Caldwell and Anthony Bell of Bell Wine Cellars. (Hmmm, perhaps someone should seriously consider compiling a reference work.) I eventually settled on clone 337 for my replants.
As for the wine in the photograph, this CS claiming to be made solely from clone 337 was an unremarkable, quotidian quaff. To be fair, I did not do a comparison tasting of this wine with another made from a different clone. However, I have comparison-tasted in the past; I have tasted clone 4 (Vinoland), clone 7 (St. Helena Sots) and clone 169 (North Avenue Negociants) side by side and they were quite distinct from one another.
Interesting stuff, I need to know more.