There were no differences in tuber K, Mg and Mn contents of both cultivars (Table 3). Tubers are a rich source of K which can be explained by K being a nutrient with high mobility required by potatoes during vegetative growth, tuber initiation, tubers bulking and maturation periods (Stark et al., 2004). Plants remove K from soil, and it is accumulated in the tubers. High levels of K can reduce Mg concentration due to competition for uptake by plant roots (Mengel, 2007). Mg, a relatively mobile element, binds atoms within the chlorophyll molecule and activates many enzymes (Marschner, 1995). Mn activates several enzymes and activates ribonucleic acid polymerase and contributes to lipid metabolism (Campbell and Nable, 1998). Low Mn levels in cvs. Tenggo and Krespo tubers could be due to its low mobility in the phloem (Kaerenlampi and White, 2009) with only a small portion of Mn in leaves transported to tubers.