Grapes may look identical, until you taste them crushed and processed for a glass of wine or cut up in a salad. Then the purple fleshed globe bursts forth with a spectacular melon flavor and a sweet fruity fragrance, while its visually identical twin has a distinctively different flavor, perhaps with a hint of musk.

In fact, today in California hundreds of varieties of grapes are grown in backyard gardens and production fields for wine, table eating and raisins.

Any wine connoisseur knows you can’t use Muscat grapes to make wine labeled as Cabernet Sauvignon. In fact, hundreds of different unique varieties of grapes are used for making wine and different ones used for fresh eating and making raisins.

This uniqueness is due in part to differences in the genetic information in the grape, which determines among other traits, its color, aroma, and taste characteristics.

That information is made up of individual chemical units strung end-to-end. If each unit is represented by an alphabetic letter, it would require 52 books, each with 1000 pages, to hold all the information needed to code for the uniqueness of a particular grape variety.

What if you wanted a new grape variety? You could use a classical breeding approach, requiring you to cross male cells, or pollen, of one variety with the female cells or eggs of another variety. You could then plant the seeds born out of that cross and screen resulting plants for the characteristics you wanted in your new variety.

What happens to all the genetic information when you do that?

You just combine all the information from the two sets of books to make 104 books, right? No, genetic rules dictate that only 52 books remain – so only approximately 50 percent of the information from each parent is kept. The breeder has no control over what information is kept, and can only observe resulting plants and choose the ones with the desired characteristics. Those characteristics are dictated by its genes – half page packets of information in the books. But grape varieties have different sets of genes that give rise, for example, to their different tastes and sugar contents.

However, predicting which traits a particular grape plant will have after a cross is difficult.

Classical breeding was used to create some traditional grape varieties, like Chardonnay, Cabernet Sauvignon and Syrah. Most of these are, however, not from recent breeding efforts but from ancient Middle Eastern or European efforts and have been multiplied over the years by cuttings, not seeds. But classical breeding is being constantly used to develop new table grape varieties with added quality or extended ripe fruit seasons.

Also widely used to alter grape in wine making have been engineered to eliminate the factor(s) responsible for causing headaches in some consumers of red wine.

Whether you consider breeding and genetic engineering the same or different depends on your perspective.

Both use the same cellular machinery to move genes around and both cause heritable genetic changes. So in that sense they are the same. However, in the case of classical breeding the change occurs inside the cell, while with genetic engineering it occurs in the laboratory. Also during breeding keeping a particular gene is a random process, while with genetic engineering specific genes are introduced.

Perhaps the most fundamental difference is that gene exchange by breeding takes place most often between plants of the same species, although gene exchange at low frequencies occurs across some species barriers. With genetic engineering the gene source can be the same crop, another crop or even different organisms, like bacteria or animals.

Why?

Because genetic information in all living things is written in the same (chemical) language. In fact humans

and plants share many (40-60 percent) of the same genes.

So, how many foods today are genetically modified (GM)? It depends on your definition of GM. If you mean in how many foods have genetic changes or modifications occurred, the answer would be all, including those grown under organic certification.

For example varieties is rootstock breeding, which involves grafting the grape producing portion of one variety onto the rootstock of another variety to provide resistance to soilborne pests and diseases. Some recent breeding efforts focused on developing grape varieties using Muscadinia rotundifolia, which is resistant to Pierce’s Disease, a problem causing costly damages to the California wine and grape industry.

In the past few decades new methods were developed to identify and move genes between grape varieties. For example, the specific grape gene(s) responsible for resistance to Pierce’s Disease could be moved from M. rotundifolia to another grape variety, like Chardonnay, including other less desirable genes from M. rotundifolia. One way these new methods are being used is to provide a genetic table of contents for the genes, which speeds up breeding efforts dramatically. Such a table of contents is being developed for the varieties with resistance to Pierce’s Disease so breeding efforts will be faster.

Another way to use the new genetic tools is to introduce specific genes to change plant characteristics,

a process called genetic engineering, recombinant DNA or genetic modifications. A single half page in the 52-thousand-page set of books can direct the plant to make new traits or to remove them. For example, specific gene(s) for resistance to a particular virus, like the destructive fanleaf virus in Europe, were identified and used to engineer grape vines, which were field-tested in France in summer 2006 for virus resistance. Also yeast strains used ancient relatives of little like modern corn. They had small seeds that could not be opened with your teeth and seed numbers per plant were also hundreds of times lower.

If the question is how many different crops have been modified by genetic engineering (GE), the number would be very small.

While many processed foods, except those labeled 100 percent organic, may contain a GE ingredient, those ingredients come from a small number of large-acreage GE crops, like corn, soy, cotton and canola.

The only whole GE foods on the market are summer squash, papaya and sweet corn. There are no GE strawberries, asparagus or grapes in production in California, although small-scale field trials have been conducted under the oversight of USDA’s Animal and Plant Health Inspection Service (APHIS).

Then grapes are just grapes, right? No, major and minor gene alterations in grapes have occurred over time, both naturally and with human help. These changes are responsible for the wonderful diversity of cultivated grapes today –from the mellow flavor of the Thompson Seedless grape to the robust taste of the Petite Sirah grape.

Such modifications occur through natural and induced mutation and gene through human intervention in gene exchange— historically through classical breeding but now and in the future through genetic engineering.

To learn more about biotechnology and its application in California agriculture you can visit the UC ANR Biotech website at: http://ucbiotech.org