Potato is an important nutrient source in human nutrition. Potato tuber quality is affected by a cultivar, environmental conditions and agricultural practices. The study examined the effect of dose (0.2 dm³ ha^–1 and 0.4 dm³ ha^–1) and date of Tytanit^® application (a single foliar application at the leaf development stage – BBCH 14–16 or at the tuber formation stage – BBCH 41–43, and a double foliar application at the BBCH 14–16 and BBCH 41–43 stages) on the tuber quality of very early potato cultivars (‘Lord’ and ‘Miłek’). Potatoes were harvested 75 days after planting (the end of June). Tytanit^® (8.5 g Ti in 1 dm³) did not affect the content of dry matter, starch, monosaccharides, protein, L­ascorbic acid or nitrates in potato tubers. The very early potato cultivars responded differently to the Tytanit^® applied. This growth stimulant caused an increase in total sugars content in the tubers of ‘Miłek’ and had a greater effect on the discoloration of tuber flesh after cooking of this cultivar. The contents of dry matter, starch, total sugars and protein in ‘Miłek’ tubers were higher than in ‘Lord’ tubers, while the content of monosaccharides, L-ascorbic acid and nitrates in tubers of both cultivars did not differ significantly.

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