In the years 1998–2001 samples of leaves, fruitlets and fruits of ‘Š ampion’ were taken from trees on six rootstocks (M.9 EMLA, M.9 T337, M.9 T339, P 22, Nr 47 and P 14). They were analysed for potassium and calcium content. For evaluation of storage ability, 24 kg fruits of uniform size were taken from each replication. After 5 months in common cold storage the incidence of diseases and disorders were determined. Leaf Ca concentration was the highest from trees on M.9 T337 rootstock. Fruitlets and fruits from trees on P 14 generally had a high K concentration. On the other hand, fruits from trees on M.9 T337 and P 22 generally had a low K concentration. Rootstocks affected storability of apples and this was related to the effect of rootstocks on fruit K:Ca ratio. Bitter pit was determined in 66% by K and in 5% by Ca concentration in the fruits. The K:Ca ratio in fruit was the factor determining bitter pit in 83 percent. The results suggest that the K:Ca ratio, irrespective of the organ analysed, may be used for further improvement of bitter pit prediction.

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