A Rainbow of Tomato Colors
Part 3 of 4
In our last article, we talked about a yellow flavonoid pigment called chalconaringenin, found in the cuticle of the skin on some tomatoes, and how this pigment can affect the color we perceive as we view the whole fruit—flesh and skin. We also talked about reds, pinks, yellows, and whites. This article will take us further into discovering more complex colors such as oranges, greens, browns, and purples that can be promoted by several different pigments.
Orange tomatoes can be caused by several different expressions. We will go over two types in this article; however, there are more combinations you may find interesting in the reference to the left of this article. The first critical enzyme in the carotenoid pathway is PSY1, which allows for orange flesh by way of the wild type dominant allele “R” (RR or Rr) that enables production of the PSY1 enzyme. The second type of orange expression can have a yellow or clear epidermis and is driven by the dominant beta-carotene allele “B” expressing higher levels of beta-carotene while reducing lycopene production. (RR;YY;BB), (RR;yy;BB)
The most common type of green-fleshed tomato is caused by a combination of the recessive “r” (low lycopene promoting yellow flesh) and the recessive “gf,” or green-flesh mutation, which promotes continued chlorophyll production. This type of green can carry a yellow or clear epidermis. (rr;YY;gfgf), (rr;yy;gfgf) The second type allows for a green flesh while still retaining a reddish core; the expression is from the dominant “Gr” (green ripe) mutation and can also have a yellow or clear epidermis. (GrGr;YY), (GrGr;yy)
Browns and purples are much the same; again, it’s the epidermis coloring that makes the distinction between the two. The flesh pigment in browns comes from a combination of higher amounts of lycopene found in the red flesh “R” gene and chlorophyll promoted by the “gf,” or green flesh, gene. Brown tomatoes must have a yellow epidermis “Y”; this is what distinguishes them from a purple. (RR;YY;gfgf)
In these, the flesh is the same as described for browns, but the epidermis expresses the recessive “y” allele for clear skin. (RR;yy;gfgf) Other expressions for brown and purple can also be affected by the expression of a high crimson (lycopene) mutation of the beta-carotene gene “Bc,” in combination with the “gf” chlorophyll promoter. Again, the epidermis color allows for the brown or purple color to come through. (BcBc;YY;gfgf), (BcBc;yy;gfgf)