Influence of lipoxygenase activity and calcium and potassium contents on bitter pit occurrence in commercial apple cultivars

The content of calcium and potassium and lipoxygenase (LOX) activity as well as the expression of LOX encoding gene in the fruit of apple cultivars that are both susceptible and resistant to bitter pit were evaluated. Fruits were collected and analyzed after harvest in the 2004 growing season and again after four months of common cold storage. The main reason was the explanation of relationship between those LOX activity and K:Ca ratio on bitter pit occurrence during storage. The biggest differences between the tested cultivars were noted in LOX activity and Ca content, followed by K:Ca ratio and the lowest potassium content. The cultivars that were resistant and susceptible but without symptoms of bitter pit exhibited higher calcium content compared to cultivars with signs of bitter pit, and with a drop in LOX activity after storage. A negative correlation was found between LOX activity and Ca content and a positive correlation was found between K:Ca ratio and LOX activity.