Zinc (Zn) is one of the essential elements in human nutrition. Its deficiency can lead to a plethora of health problems, including stunted growth and poor development, secondary immune deficiency, diabetes, hypertriglyceridemia and different forms of cancer. World Health Organization estimates that on a daily basis, around 2 billion people do not consume enough Zn. One of the key and affordable ways to increase Zn intake is by introducing nutritionally rich crops into our diets. Different millets have been endorsed as perspective candidates, as they posess many favourable nutritional and agronomic traits. Proso millet (Panicum miliaceum L.) has been cultivated and consumed on Slovenian territory for over 3000 years, with proso millet porridge representing one of the staple dishes for farmers. The aim of this study was to grow six Slovenian populations and one variety of proso millet in pots and evaluate their Zn-use efficiency at two developmental stages: at flowering and at maturity. Using X-ray fluorescence spectrometry, we determined that there are differences in Zn-use efficiency between populations, with the most efficient being variety Sonček, and the least efficient being population Odranci. The differences in Zn concentrations in different tissues were smaller at flowering stage than at maturity. Furthermore, populations exhibiting higher concentrations of Zn in their leaves during flowering exhibited higher grain Zn concentrations. We used micro-particle-induced X-ray emission to determine tissue-specific Zn concentrations in grains of Sonček in Odranci, and identified scutellum to contain the highest Zn concentrations followed by Zn concentrations in embryo, aleurone, endosperm and husk. The difference in the overall concentration of grain Zn between Sonček and Odranci originates from a higher accumulation of Zn in the scutellum of variety Sonček than the scutellum of population Odranci.
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