In precise field trials in the years 2004-2008 in the Czech Republic the effect of conditions of location, variety and mineral fertilization on ascorbic acid content (AA) in potatoes with different ...tuber flesh color was investigated. Significant was the effect of variety. The Marabel variety with the highest AA content (248 mg/kg FW) exceeded other eight varieties by 13.4-74.1%. The Valfi variety, in five-year trials the only variety with purple colored flesh, ranked among analyzed varieties moderately below average. In addition, in the year 2008 the group of seven varieties with purple and red tubers was evaluated and AA content lower by 15.2% compared to the group of varieties with yellow flesh was determined. Also, significant differences were determined between the varieties with coloured tubers; the highest AA content was found in the red-fleshed variety Highland Burgundy Red (234 mg/kg FW). A negative effect on AA content in tubers was observed at increased intensity of N fertilization (at 180 kg N/ha, AA decreased by 12.4% compared to 100 kg N/ha). Enhanced levels of potassium and magnesium fertilization had no effect on the AA content. The effect of location on AA content was not shown; however, from the four locations in average of five years a pronounced trend of the highest content of ascorbic acid on the location Přerov nad Labem with the highest temperature averages during vegetation period of experimental years was determined (by 0.9°C, 2.3°C, and 5.9°C higher compared with other locations).
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