A Rainbow of Tomato Colors
Part 2 of 4
In the previous article, we talked about the phytonutrients that express the pigment colors in tomatoes. To recap, there are three basic classes of pigment pertaining to tomatoes. The first is chlorophyll, expressing shades of green in unripe tomatoes, in green-when-ripe tomatoes, in some forms of stripes, and in combination with other pigments to create shades of purples and browns. Second, we looked at carotenoids; these are the pigments that express shades of yellow, orange, and red. The third class of pigments we shared were in the flavonoid family. Chalconaringenin is a yellow flavonoid found in the cuticle of tomato dermal layers (skin), which is transparent, allowing the color of the flesh beneath the skin to be seen through a yellow filter. Lastly, we talked about anthocyanins, which are their own subclass of flavonoids and contain the darkest of pigments, such as deep purples, blues, and reds. These are found primarily in the epidermis and can show a slight “bleed” of their color into the flesh beneath.
Now let’s look at the epidermis, or skin. We talked briefly above about chalconaringenin, the yellow pigment found in the cuticle of the epidermis. This small change in the skin layer can alter how we perceive flesh colors in a major way. It can make a red-fleshed tomato appear red, but if that gene is missing, making the skin clear with no yellow tint, the red flesh will appear pink. The gene responsible for this yellow skin will be shown with “Y” (as it is a dominant trait), and the gene for clear skin “y” (as it is recessive). Read carefully as we break down the color ways, and you will see the pattern between reds and pinks, browns and purples, and yellows and whites.
This next section gives basic descriptions of each color class and the genotype associated with it. References will be listed at the end of this series for more in-depth research.
Reds and Pinks
Red tomato flesh is largely pigmented by lycopene (red) with lesser amounts of beta-carotene (orange), expressing the red gene “R.” The yellow skin pigment (chalconaringenin) is expressed here also, showing the “Y” gene. (RR;YY) Like the red tomato flesh, pink tomato flesh contains lycopene and beta-carotene expressing the red gene “R,” but here the epidermis is clear, expressing the recessive allele “y.” (RR;yy)
Yellows and Whites
Yellow tomato flesh is pigmented by a recessive allele of the red gene “r,” where the synthesis of lycopene is suppressed. Yellows can express either a clear skin “yy” or a yellow skin “YY.” (rr;YY) or (rr;yy). A white tomato is caused by the flesh expressing an even stronger suppression of lycopene, the recessive allele of the red gene “r-.” A white tomato will always have a recessive clear skin “yy.” (r-r-;yy)
Please check back soon for the next article in this series!