The colour of potato flowers and tubers
According to research carried out during the nineteen thirties, flower colours in the potato fall into two groups, coloured and white. The coloured group may be subdivided into a) red and brownish purple and b) blue and bluish purple. In both cases the colour intensity goes from very pale to very deep. In coloured flowers the tips of the petals may also be white. In addition, some of the white flowered class possess a small amount of pigmentation.
White flower colour is usually recessive to coloured. However, white crossed with white sometimes gives coloured forms. It seems that genetically different white - flowered varieties exist.
The experiments carried out on the inheritance of Anthocyanin in various parts of the plant show that pigmentation is governed by three main types of gene:
1) a basic gene (as opposed to acidic)
2) a red producing gene
3) a blue producing gene
4) an anthocyanin inhibitor
There is also evidence of a number of duplicate or similar genes controlling pigmentation. Certain of these genes are not identical, though they are closely similar in their effects. Some of the genes are independent, but some are not. The inheritance of colour in potatoes is of considerable interest but it is very complex. I have been unable to find any information on this topic later than that published by Crane and Lawrence in the 1930s. It is clear, however, that many of the potato plants with pigmented flowers are also coloured in their stems and tubers.
The colour of potato tubers
The flesh colour of tubers may be yellow, white, purple coloured by anthocyanin, or red. In addition, potatoes may turn green on exposure to light due to chlorophyll formation.
White is usually recessive to yellow, so white x yellow will give yellow, though occasionally if you cross yellow with white you get white. There are yellow fleshed forms which breed true, and there are others which give yellows and whites in the ratio 15: 1.
When I self pollinated the the variety Salad Blue, there was a wide range of tuber colours in the resulting plants. Some were darker than Salad Blue; others showed a blue ring underneath the skin, and in the rest there was every shade between blue and white. There was no obvious dominance of one colour over another, or of blue over white. Coloured skin usually meant coloured flesh, but a small proportion of the tubers had blue skin and white flesh. No tubers had white skin with blue flesh. A very small proportion of the tubers had yellow skin and yellowish - white flesh. Click on Potato Tubers - pictures and go to page 2 to see the photographs.
Nigel Deacon, Diversity website.
I have taken some of the information above from the book "The genetics of garden plants" by Crane and Lawrence, published by Macmillan in 1934.
