StrepbyStrep: Flower Color Genes in Streptocarpus by Dr. Jeff Smith

Flower Color Genes in Streptocarpus

Dr. Jeff Smith

Indiana Academy
Ball State University
Muncie, IN 47306
[email protected]


During my work with the flower color genetics of African violets, I found several articles on the flower color genetics of Streptocarpus that were published in the 1950's by Lawrence and Sturgess. If you are hybridizing with Streptocarpus, I would urge you to read the original articles, but the following is a quick summary of their reports.

Genes:
V = places pigment in the flower stems.
F = places pigment in the petal cells.
V and F are both necessary to give "color", but do not control "which color". These genes are similar to house keys that let a painter in the house, but they don't control what color he will paint the rooms. When V or F are recessive (vv or ff) the flowers will lack any color and will be white in appearance.

I = color intensity. II = intense color, Ii = medium color and ii = pale color.
This gene doesn't control "which color", just how "intense" the final color will be in appearance.

The actual flower color genes (O,R,D) are very similar to that of African violets, although the names given to the visible color are somewhat different. The names of the colors and their genotype codes are given below. Where the second copy of the gene is given as a "_", the second copy can be a dominant or a recessive. For example, in Blue flowers, only one dominant of each the three genes is needed.

Blue = O_R_D_
Magenta = ooR_D_
Pink = oorrD_
Mauve = O_R_dd
Rose = ooR_dd
Salmon = oorrdd

The Blue-Magenta-Pink series is the same as the Blue-Fuchsia-Pink series in African violets. The Mauve-Rose-Salmon series is the same as the Coral Blue-Coral Red-Coral Pink series in African violets.



Other genes affect the pattern of color or modify the final color. Some of these genes are:

B = gives a blotch of color in the throat of the bloom. The recessive "bb" produces flowers without a blotch. The trait appears to produce a darker or more intense version of the color of the outer edges of the petals. Thus, you can get dark pink blotches on a lighter pink flower etc.

H= gives color on the capitate hairs of the pistil. The recessive "hh" gives white or colorless hairs.

Genes F,I,B, and H are very closely linked and are usually inherited as a single unit. Therefore, many plants have pigmented flowers with at least medium intense color and blotches in the throat or have white flowers without blotches.

C = adds a co-pigment to the flower color. This gene modifies the appearance of the color, giving a bluish tint to the overall color. Plants with the recessive "cc" combination have flowers that are "brighter" in appearance. In the Mauve-Rose-Salmon series, the dominant gene produces undesirable murky colors.

L = puts nectar guides in the flower tubes. The recessive "ll" produces flowers without the lines.

Y = puts a yellow central stripe in the flower tube. I suspect that the size of the yellow area changes with "YY" versus "Yy" plants. The recessive "yy" would produce flowers with no yellow in the flower tube.

This is a beginning list. Other genes are mentioned in the original articles, but they appear to involve some rarely seen color modifications. Genes for plant size, fragrance etc. were not mentioned in these articles.


References:

Lawrence, W.J.C. and V.C. Sturgess. 1957. Studies on Streptocarpus. III. Genetics and
Chemistry of Flower Colour in the Garden forms, Species, and Hybrids. Heredity 11:
303-336.

Lawrence, W.J.C. 1957. Studies on Streptocarpus. IV. Genetics of Flower Colour
Patterns. Heredity 11: 337-357.

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