Comparison of the ability of fifteen onion (Allium cepa L.) cultivars to accumulate nitrates

Abstract

The aim of a two-year study was to characterise selected Allium cepa L. genotypes with regard to their ability to accumulate nitrates in bulbs as well as to search for a possible relation between NO₃^- concentration and dry matter content. Fifteen cultivars of edible onion, mostly of long-day genotype with different growing periods, bulb size and skin colour, were taken for the experiment. Seeds of particular cultivars were obtained from the following seed companies: Spójnia Nochowo (‘Labrador’, ‘Takstar F₁’,‘Tęcza’, ‘Warna’, ‘Zorza’), Polan (‘Polanowska’, ‘Topolska’), PlantiCo Gołębiew (‘Alibaba’, ‘Efekt’, ‘Kristine’, ‘Niagara F₁’),and PlantiCo Zielonki (‘Bila’, ‘Irka’, ‘Wenta’, ‘Zeta’). Plants produced from seedlings were grown in the experimental field of the University of Agriculture in Kraków. After crop harvesting and additional drying, nitrate and dry matter content in bulbs of all cultivars were measured.

The following cultivars: ‘Efekt’, ‘Labrador’ and red-skinned ‘Wenta’, were characterized by the lowest ability to accumulate NO₃^- in bulbs. The highest nitrate content was noted in bulbs of ‘Takstar F₁’ (a very early-season cultivar), followed by ‘Bila’ and ‘Tęcza’. A weak, yet statistically significant negative correlation between nitrate and dry matter content was observed. The highest dry matter content was determined in bulbs of white-skinned ‘Alibaba’, while the lowest – in brown-skinned ‘Labrador’.