Tomato Fruit Color Mutations



What makes a tomato's color?

Tomatoes are found in a range of colors; red, yellow, white, pink, green, purple, brown and "black".
These colors are influenced most by two traits for skin and flesh. Starting off green from cholorophyll, as tomatoes ripen most if not the chlorophyll gets converted into various pigments called carotenoids. Ripened flesh color will depend on the amounts and types of various carotenoids. 

Skin

The skin, or epidermis, of the tomato is found in two various colors, clear and yellow.
The color of skin will effect the outside appearance of the flesh. When the flesh is red (r+) the outside will either apprear red (yellow skin) or pink (clear skin).

This is controlled by a single recessive gene y.
y+ (wild type) is dominant and results in yellow skin. When y is expressed in a recessive pairing the result is clear skin.

y+y+ = yellow skin
y y    = clear skin

Examples of flesh and skin interactions


Several other genes can effect the skin and color of a tomato. Most notably gs or "green stripe". Here certain parts of the epidermis have more chlorophyll. In unripe fruit stripes of darker green appear randomly. On ripe fruits these stripes appear as yellow or golden. Examples of such fruit are "Green Zebra" or "Stripped Stuffer".
The green stripe gene also interacts with the yellow skin gene to produce variations in the color or intensity of the stripes.

green stripe variation due to skin color


Flesh

The flesh, or pericarp, of the tomato is the interior tissue of the fruit. Genetics control the process by which the chlorophyll of an unripe fruit may or may not be converted into other pigements. These pigments are called carotenoids. Depending on the color, various carotenoids such as lycopene, beta-carotene, delta carotene and others are expressed giving the tomato fruit its overall color. These pigments not only effect fruit appearance but the also influence nutrition and flavor as well. Various genes for control of flesh color can be expressed at the same time. Below are examples of red flesh + green flesh and other colors expressed with the bicolor trait at the same time.

Sometimes the gene for "green flesh" inhibits the breakdown of chlorophyll. It is interesting because it can really alter the "look" of a fruit (and I think taste as well). It has different "alleles" or forms which are slight variations to the expression of the gene. It is probably not likely most would catch the subtle variations between the different alleles but when green flesh and red flesh are expressed together there can be subtle differences to the flesh color. Fruit may appear "brownish", purplish or what some call "black". Examples of these variations would be "Cherokee Purple", "Black Plum", "Black Krim" and "Purple Haze". An example of both expressed together can be seen in the image above. Variations in the color may also be due to alleles for the expression of "red" which have yet to be discovered by molecular gene sequencing.

Green flesh also interacts with the gene for yellow flesh. When both genes are expressed together the result is a green flesh. Yellow flesh also has different alleles. So in some cases it seems that when certain yellow types interact with green flesh, the result is a "white" flesh (like "White Queen"). Below is an example of a typical green color (yellow flesh + green flesh) from a hybrid green line I developed.


Tomato Mutation Genes Effecting Appearance




This is no means a complete list and was adapted from the TGRC's List of Gene Names and Symbols. Specific genes and alleles are italicized. Gene names are linked to photos when applicable. References refer to alternate pictures or articles in The Tomato Genetics Cooperative,  research abstracts, release information or relevant examples.

References Guide:
  • numbers (1,2 etc)  are additional images
  • low case letters refer to research papers or notes
* articles require one to scroll down the page to find specific reference

Gene Name
syn
or allele
Use 
 
Description
Reference

Abg

Aubergine

---

color


Fruit epidermis purple, particularly on shoulder and where exposed to direct light; also enhanced by wounding.

1, 2

Af
Anthocyanin fruit
---
color

Anthocyanin in green and ripe fruit; environmentally sensitive, absent when shaded
1
alc
alcobaca
---
ripening

Greatly delayed fruit ripening processes.
a , b, c ,d
at
apricot
---
color

Yellow-pink color of fruit flesh
flower, 1,
a*, b, c , d
atv
atroviolacium
---
appearance

Excess anthocyanin on leaves, stems, and fruits

aur
aurantiaca
aur1
color

Small, pointed, yellowish light-green pinnae; orange fruit

B
Beta-carotene
---
color/
nutrition

High Beta-carotene, low lycopene in ripe fruit.
1,2
a , b , c , d , e
Bc
crimson
ogc
color/
nutrition

Increased fruit lycopene content; phenotype similar to Bog.
a , b
Bm
minutum
---
color/
nutrition

High Beta-carotene, low lycopene in ripe fruit.

Bog
old gold
og
color/
nutrition

Corolla tawny orange; increased fruit lycopene
flower
Del
Delta
---
color/
nutrition

Reddish-orange mature fruit color, due to inhibition of lycopene, and increase of delta-carotene.
a, b, c, d,
dg
dark green
---
color

Immature fruit color normal; darker green color appears as fruit develops, then persists until onset of ripening, high chlorophyll compared to normal or hp
a, b,
dps
diospyros
---
color

Fruit tissue is dusky orange.

fp
fruit pox
---
appearance

Many small dark green spots on immature fruit, rupture prior to ripening.

Fs
Fruit stripe
---
appearance

Fruit with dark green radial stripes opposite locules

Gdf
Gold Fleck
---
color

Small dark green spots on immature fruit, do not rupture but turn yellow on ripe fruit.

gf
green flesh
---
color

Persistent chlorophyll giving ripe fruit purplish-brown color.
1
a, b, c, d, e
Gr
Green ripe
gr
color

Resembles gf, except that center of fruit turns red.
a*, b
gs
green stripe
---
color/
appearance

Radical green stripes in epidermis of unripe fruit; golden in ripe fruit
1
a, b
hp-1
high pigment
hp-2
color/
nutrition

Chlorophyll, carotenoids, ascorbic acid content of fruit intensified. Anthocyanin expression in seedling roots
1, 2, 3
a , b, c, d, e, f
nor
non-ripening
---
ripening

Very retarded pigmentation, non-softening, and crack resistance of fruits.
1, 2
a, b ,c*, d, e
Nr
Never ripe
Nr-2
ripening/
color

Fruits ripen slowly to dirty orange color; homozygous viable.
1, 2
a, b, c
p
peach
---
appearance

Fruits with dull hariry surface.

r-
yellow flesh
---
color

Yellow color of ripe fruit flesh
1
a*,b
, c
rprov4
yellow flesh
---
color

Yellow color of ripe fruit flesh

rprov5
yellow flesh
---
color

Yellow color of ripe fruit flesh

ry
yellow flesh
---
color

Reddish yellow: Likely allele of r with streaks of random reddish flesh tones in ripe fruit
a, b
r(2s)
yellow flesh
(2s)
color

Yellow fruit flesh; lighter yellow flowers

r(1s)
yellow flesh
(1s)
color

Yellow color of ripe fruit flesh.

rin
ripening inhibitor
---
ripening

Fruits green at maturity, later turning bright yellow, retarded ripening.
1,2
a
sh
sherry
---
color

Fruit flesh yellow with reddish tinge

t
tangerine
---
color

Fruit flesh and stamens orange colored.
1
a*, b, c, d, e, f, g, h
u

uniform ripening
many
ripening/
appearance

Unripe fruits of uniform light green color, lacking normal darker shoulder.
a*
vo
virescent orange
---
color

Yellow virescent; mature leaves pale bluish green; fruit flesh orange, redder in outer walls.

y
colorless fruit epidermis
---
color/
appearance

Fruit epidermis lacks pigmentation (clear skin).
a, b, c

* articles require one to scroll down the page to find specific reference



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