Induction of bitter pit in apple

Abstract

A field study was conducted to induce bitter pit in cultivar ‘Sundale Spur Golden Delicious’ ( Malus domestica Borkh.) apple. Fruiting spurs were sprayed with 1% (w/v) CaCl 2 and 1% (w/v) MgCl 2 every 10 days, beginning 5 days after full bloom, and/or shaded with brown paper bags. The effect of MgCl 2 spray and bag + MgCl 2 treatments on the fruiting spurs was increased bitter pit incidence, decreased fruit calcium, increased fruit magnesium and potassium, and decreased number of fruit per spur. Bagging the fruit resulted in a 4-fold increase in bitter pit incidence, and a significant reduction in fruit calcium content and fruit weight over the control. In contrast, CaCl 2 spray slightly reduced bitter pit, increased fruit calcium, reduced fruit magnesium and increased the number of fruit per spur. The incidence of bitter pit ranged from 8% (CaCl 2 spray alone) to 88% (bag + MgCl 2). Overall, the combinations of bagging and cation sprays induced a wide range of bitter pit incidence in apple fruit which can be reliably used for future study of the disorder.