Abstract: This study aimed to investigate the physiological mechanism behind the resistance of apples to postharvest gray mold. ‘Qinguan’ and ‘Fuji’ apple fruits were wounded and inoculated with Botrytis cinerea Pers. The changes in compounds and enzyme activities related to the disease resistance in flesh tissue were measured during subsequent storage. The results indicated that disease incidence and lesion diameters in ‘Qinguan’ apples were significantly less than those in ‘Fuji’ apples after inoculation (P < 0.05). Moreover, the activities of phenylalanine solution ammonia lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO), chitinase (CHI) and β-1,3-glucanase (GLU) in the pulp of resistant varieties were higher than in susceptible varieties, facilitating the accumulation of flavonoids and lignin, reducing membrane lipid peroxidation, decreasing the production of malondialdehyde (MDA) and consequently increasing the disease resistance of fruits. However, the total phenolic content of ‘Qinguan’ apples was lower than that of ‘Fuji’ apples. These results provide a theoretical guidance for identifying the resistance of apples to postharvest gray mold and for screening resistant varieties.

Key words: apple, gray mold, resistance, physiology