Tomato Genes

Those of us who have at one time or another, eaten tomatoes fresh from a home garden know that they taste much better than anything you can buy in a grocery store.  That is primarily because home-grown tomatoes are allowed to ripen on the vine, while the store-bought varieties are picked while they are still a light green and allowed to ripen on the way to the supermarket.

It might also explain the recent interest in Heirloom tomatoes. – consumers willing to pay significantly more to buy a tomato that is ugly, but tastes better,

Now, a new study reveals that decades of breeding the fruits for uniform color have robbed them of a gene that boosts their sugar content.  For about 70 years breeders have selected tomatoes that are uniformly light green. This makes it easier to spot the tomatoes that are ready to be harvested and ensures that, by the time they hit supermarket shelves, the fruits glow with an even red color. Wild varieties, in contrast, "have dark green shoulders, and that makes it harder to determine the right time to harvest.

Scientists at UC, Davis have now determined that years of breeding for uniform size, shape and color has led to a tomato that is almost tasteless because of genetics.  A gene known as SlGLK2—a so-called transcription factor, which controls when and where other genes are switched on or off. In most tomatoes on supermarket shelves,  SlGLK2 is inactive. While the mutation was beneficial to farmers, it's not such a sweet deal for consumers. Chloroplasts use the light energy they capture to convert carbon dioxide and water into sugars. Tomatoes with a mutated SlGLK2gene not only have fewer chloroplasts, they also sport less sugar. By inserting an intact copy of the gene into tomatoes, the researchers increased the amount of glucose and fructose in ripe fruits by up to 40%, the authors write in the paper, published online today in Science. The content of lycopene, an antioxidant that could have significant health benefits, was also increased.