Effect of natural and growing conditions on the contentof phenolics in potatoes with different flesh colour

In precise field trials in the Czech Republic from 2004-2008 the impact of location conditions, varieties with yellow, purple and red flesh and mineral fertilization on the content of total polyphenols (TP) and chlorogenic acid was investigated. The highest TP contents were reported at two locations with extreme climatic conditions; in those under stress due to low temperatures in the vegetation period at the mountainous area Stachy (5.89 mg TP/g DM) and those under drought stress in the warm lowland location Přerov nad Labem with light sandy soil (5.81 mg TP/g DM). The five-year experiment with the purple-fleshed Valfi variety (13.29 mg TP/g DM) reached 2.46 to 3.18 times higher content of TP in comparison with eight yellow-fleshed varieties. The yellow-fleshed Karin variety (5.39 mg TP/g DM) outperformed TP content of other yellow-fleshed varieties by 3.1 to 29.1%. In another experiment conclusive differences between the eight varieties with purple and red flesh were found; the highest TP content was detected in cv. Violette (25.9 mg TP/g DM) with the darkest purple flesh. As to the chlorogenic acid content similar relationships between varieties were found as in the case of TP. High linear correlation (r = 0.8536) was found between the content of chlorogenic acid and the content of TP. Among the treatments of mineral N, P, K and Mg fertilization, the content of TP was only affected by a treatment with a higher dose of K and Mg, causing a decrease in TP content.