In previous articles, we discussed different pigments that promote what our eyes see as “single” colors—red, pink, yellow, white, orange, green, brown, and purple—in tomatoes. Today, we will go over some more involved colors, the bicolors, tricolors, and anthocyanin-tinted tomatoes.

The bicolor expression happens when the carotenoid pathway is triggered or expressed in parts of the tomato flesh but not all; we generally tend to see red streaks dispersed throughout the flesh of a different color. The gene responsible for this activity is a mutant allele of the “R” gene named “ry.” In a yellow flesh, the bicolor genotype would be labeled (ryry); however, in a green-fleshed fruit bicolor, the genotype label would be (ryry;gfgf). Some examples of yellow flesh bicolors are Hillbilly, Pineapple, and Nature’s Riddle. Some examples of green bicolors are Captain Lucky, Wild Thyme green when ripe, and Copper River. Beyond these two known types of bicolor, there are many more yet to be explained scientifically. Some evidence even suggests there are tricolors that are visible to our naked eye. We are hopeful that new findings will be discovered and recorded.

Last but not least, we come to anthocyanin-pigmented tomatoes. This, by far, is probably the trickiest to explain as far as fruit coloring goes. Anthocyanin is a pigment found primarily in the epidermis of the fruit, although it’s been known to “bleed” slightly into the flesh on some varieties. It can also follow striping patterns when combined with the fruit strip (Fs) gene. There are two genes responsible for this pigment in tomatoes: anthocyanin fruit (Aft), which expresses this pigment in epidermal layers of the fruit, and atroviolaceum (atv), which expresses anthocyanin in the fruit’s epidermis and in the plant itself. Aft is expressed by UV exposure, sort of like a suntan that deepens with more exposure. Aft and atv also tend to express more with cooler temperatures. These types of tomatoes are the newest, and many trials and studies are still being carried out since the introduction of the first marketed fruits by Oregon State University (see reference); previously, it was a trait seen only in wild tomatoes.

We hope these articles have imparted some valuable information, not only about the color of tomatoes but also about the health benefits they offer. As you plan your gardens for next season, step outside of the box and try growing a rainbow of tomatoes . . . maybe you’ll find a new favorite. We thoroughly enjoy feedback from our readers, so we will leave you with this question: What is your favorite color of tomato?