Potato is by far the most important non-cereal staple food for mankind. It is the fourth crop in global production terms and a long-established part of the diet in many parts of the world, including the UK. Potatoes are not only an excellent source of carbohydrate and fibre but are also a valuable source of vitamin C, a number of minerals including iron and potassium, and other phytonutrients including carotenoids.

Potatoes vary greatly in the levels of tuber carotenoids. Some of the rich yellow fleshed genotypes popular in some Andean countries (Figure 1, below), grown under the name Yema de Huevo (‘Egg yolk’), have particularly high levels of carotenoids. Our research on the genetics of natural variation in carotenoids in tubers builds on the work of Mark Taylor’s research group in Plant Products and Food Quality which has investigated the manipulation of genes for enzymes in the biosynthetic pathway. We are now collaborating with other European groups in the project EU-SOL to determine the genetic and molecular basis for natural variation in these compounds. This project supports a PhD student, Ray Campbell, currently working on populations segregating for carotenoid type and amount.

Figure 1: A tuber of the high carotenoid Phureja variety Yema de Huevo.

Using a combination of genetic mapping of an F1 population from crossing between two heterozygous diploid with AFLP and SSRs, microarray analysis, and the development of polymorphic markers for candidate genes, it has now been shown that the key locus for the overall level of carotenoids in potato tuber flesh is one of the beta-carotene hydroxylase genes, crtR-b2 (Figure 2, below).

Figure 2: Markers of different size for the crtR-b2 gene determining the carotenoid content of potatoes.

Additional work using microarrays to investigate gene expression together with further genetic mapping using new types of molecular marker are underway to reveal further detail of the control of individual carotenoids in our mapping populations.