CULTIVAR VARIATIONS IN APPLE WAX COMPOSITION

Abstract

Apple cuticular wax is the primary environmental interface between the fruit and pathogens or protectant chemicals. Analyses have shown quantitative and qualitative differences in wax of apple cultivars grown in various environments. Of the twelve major wax components, seven exhibited significant variations between Golden Delicious(GD) and Red Delicious(RD) cultivars in all three years. Of these seven components, two compounds occur in greater concentrations in RD than in GD cultivars, one which elutes soon after hexacosanol comprises 10 to 15 % of the RD wax composition verses less than 0.5 % in GD. The other compound comprised 5% of the RD wax verses 1-2% in GD. The other five compounds were found in greater concentrations in GD than RD cultivars. Tetracosanol and another early eluting unknown compound each make up 1 to 3.5 % of GD wax composition while appearing in only trace amounts in RD cultivars. Hexacosanol and a third later eluting unknown each constitute 2 % of GD while concentrations in RD were consistently 1 % or less. Ursolic acid, appears as two isomers, the first isomer constituted 12 to 16 % of GD wax and only 8 to 9 % of RD cultivars. Nonacosane and the major isomer of ursolic add constituted 50 to 70% of the total wax of each cultivar and were not significantly different.