Effects of preharvest nitric oxide treatment on ethylene biosynthesis and soluble sugars metabolism in ‘Golden Delicious’ apples

• Preharvest sodium nitroprusside (SNP treatment increased the NO content in ‘Golden Delicious’ apples.
• Preharvest SNP treatment inhibited ethylene metabolism.
• Preharvest SNP treatment promoted the accumulation of sucrose.
• Preharvest SNP treatment might be a potential measure for ripening control.

In order to examine the influence of preharvest nitric oxide (NO) treatment on ethylene biosynthesis and soluble sugar metabolism in ‘Golden Delicious’ apples, apple trees were sprayed with 50 μM sodium nitroprusside (SNP) (a donor of NO) 14 days before harvest. The results indicated that preharvest SNP treatment can increase the NO content and the NOS activity in apple fruit, therefore, delay the accumulation of ethylene due to its inhibition on the activities of 1-aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxydase (ACO). Fructose is the main sugar in ‘Golden Delicious’ apple. The synthesis of sucrose was stimulated and the decomposition of sucrose was inhibited by this treatment, thus causing the accumulation of sucrose. We can draw a conclusion that pre-harvest SNP (50 μM) treatment can increase the NO content of fruit during storage, while higher NO content can further regulate fruit ripening through its effect on ethylene and sugar metabolism in ‘Golden Delicious’ apple fruit during storage at 18 °C.