Submitted to: American Journal of Potato Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/8/2006
Publication Date: 5/1/2006
Citation: Brown, C.R., Kim, T.S., Ganga, Z., Haynes, K.G., Dejong, D., Jahn, M., Paran, I., Dejong, W. 2006. Segregation of total carotenoid in high level potato germplasm andits relationship to beta-carotene hydroxylase polymorphism. American Journal of Potato Research. 83:365-372. Interpretive Summary: Potatoes have many metabolic products in the tubers that are not very well known to the general public. All potatoes some level of a pigment class called carotenoids. These are everywhere present in plants and are often responsible for the yellow to orange color of fruits and vegetables. They are fat soluble and easily extracted from plant parts using organic solvents. The American consumer is accustomed to white flesh potatoes. However, potatoes grown in the Andes, where the potato originally evolved, are often yellow in color. Some of these are very deeply colored. This group is called the “Yellow Potatoes.” This study has shown that in a genetic cross between two Yellow potatoes from South America the concentration of total carotenoids can vary from 4 to 26 times that of white flesh potato. Also it was possible to attribute a portion of the variation to distinct forms of an enzyme that is part of the carotenoid synthesis. Although the gene in question showed a partial responsibility, it is interesting to note that we do not know what is exercising the remainder of the control over carotenoid concentration. Very high carotenoid potatoes have the potential of being therapeutic nutritionally in macular degeneration, an eye disease that responds favorably to administration of high doses of lutein, the main carotenoid in potato.
Technical Abstract: Carotenoid concentrations were determined among the progeny of a cross between two high carotenoid lines derived from diploid Papa Amarilla germplasm from South America. The total carotenoid content ranged from 82 to 2686 micrograms per 100 grams fresh weight. The higher values greatly exceeded the mid-parent value of the cross. A yellow tuber flesh color index was determined for a subset of the progeny. A cleaved amplified polymorphic sequence (CAPS) assay was developed to distinguish the alleles of beta-carotene hydroxylase (bch) in the two high-carotenoid parents. A bch allele (denoted B) common to the high carotenoid parents co-segregated with yellow flesh in the progeny of a white flesh x yellow flesh cross, making bch an excellent candidate for the classical Y locus, required for yellow tuber flesh. The same allele was also present in all other yellow flesh potato clones tested. Genotype at bch explained a portion of the variation of total carotenoid (R2 = 0.42). Clones homozygous for the B allele (BB) contained, on average, slightly more carotenoid than heterozygous Bb clones, which in turn had much more carotenoid than homozygous bb clones, suggesting a partially dominant gene model. Similarly, bb flesh was significantly less yellow than Bb and BB, the latter two being quite close. Total carotenoid varied considerably among progeny in the Bb and BB genotype categories suggesting that variation at one or more additional loci have a significant effect on total carotenoid levels. High carotenoid potato may have particular value for human health due to the antioxidant properties and the therapeutic value for eye health in patients at risk for macular degeneration.