Dose effect of exogenous abscisic acid on controlling lignification of postharvest kiwifruit (Actinidia chinensis cv. hongyang)

Abstract

Postharvest ‘Hongyang’ fruit is susceptible to low temperature in storage, which results in black patches on the peel and lignification in the pulp. Abscisic acid (ABA) has been shown to enhance the cold tolerance of many other postharvest fruits. This study investigated whether applying ABA can control chilling injury (CI) of ‘Hongyang’ during storage at 0 °C. Fruit were pretreated with 0–50 mg/L ABA, and then the CI symptoms and lignin accumulation processes were analyzed and microscope observations were performed during low temperature storage. The results showed that there is dose effect on controlling lignification. For example, 50 mg/L ABA treatment increased phenylalanine ammonialyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD) activity, which are crucial for lignin synthesis, and sharply upregulated expression of the AcPAL, AcCAD and AcPOD genes. However, 20 mg/L ABA alleviated black patch symptoms, increased lignin content in the peel, and did not negatively affect fruit quality. The higher total antioxidant capacity (ORAC) of edible part was maintained by 20 mg/L ABA treatment. Furthermore, microscope observations showed that 20 mg/L ABA decreased the number of lignin cells with a diameter of 40–80 μm, thus reducing the chance of lignification in the pulp.