My winemaking career began in the year 2000 after my wife Elisheva and I decided to purchase 209 acres of raw land in the Shenandoah Valley AVA in El Dorado County. Within a couple of years, we built a winery and planted 20 acres of vineyards, which were expanded to 45 acres over the years. I consider myself a farmer and a grape grower as much as a winemaker.
One of my most significant achievements as a grape grower has been my success to grow Cabernet Sauvignon grapes in this region. I can attribute this success to two factors: changing the architecture of my trellis system to provide shading of the side of the vineyard facing the afternoon sun, along with the proper clonal selection of the Cabernet vines. I find the concept of clones and clonal selection most fascinating and decided to discuss this subject in this month’s Winemaker’s Corner.
A clone is defined as a genetically uniform group of plants, derived originally from a single plant by asexual propagation, mainly by grafting. All plants derived from one clone are expected to be identical.
On the other hand, when selections of vines of the same variety from different sources and locations are compared, one may find subtle to significant differences. These differences are magnified when a plant is relocated from one environment to another. In the beginning the new environment will seem hostile. In an effort to survive, the plant will try to acclimate, adjust and change. The changes that occur in the plant are known as mutations. Over time, mutations may accumulate creating a potential of affecting the fundamental characteristics of the plant, such as the size of the berries, the shape of the cluster, the color, the flavor profile, disease resistance, harvest time, yield and more. A selection of plants that undergoes this level of changes are known as “clones” of a variety.
A classic example of clone diversity is Zinfandel and Primitivo. They both originated from a Croatian variety known as Crljenak Kastelanski, which migrated to Italy to assume the name Primitivo and separately to America where it was called Zinfandel. These two clones having identical DNA’s, were separated for 200 years growing in very different environments. I grow both clones in my vineyard and can tell you that they are fundamentally different: Zinfandel has big and very tight clusters with large berries, while Primitivo has smaller and looser clusters with small berries. The flavor profile of the two wines is also quite different. Furthermore, Primitivo has a higher level of tannins and denser color than Zinfandel. They definitely don’t look alike.
Going back to our Cabernet project, I attribute our success to the selection of clones that are able to withstand the rigors of our hot weather. Most of the common clones of Cabernet find our weather too harsh, which prevents them from going through the process of normal ripening.
One final note: In addition to cloning, which is asexual, plants can also be created by sexual propagation by either man or Mother Nature. An example of a manmade variety through sexual propagation is Petite Sirah, created by crossing Syrah with an obscure variety called Peloursin. A more famous variety created spontaneously in nature by sexual propagation is Cabernet Sauvignon, a crossing of seeds of Cabernet Franc and Sauvignon Blanc. My question to you is this: Can we duplicate Cabernet Sauvignon by crossing seeds of Cabernet Franc and Sauvignon Blanc? I think you know the answer. You can duplicate Cabernet Sauvignon sexually, as much as you can duplicate your son Joe. The only way to have Cabernet Sauvignon is by cloning. Get it?