Abstract: In order to investigate the effect of 24-epibrassinolide (EBR) treatment on postharvest black spot and reactive oxygen metabolism of apricot. ‘Saimmaiti’ apricot fruit were soaked with 0.9 mg/L EBR under reduced pressure or distilled water as a control, dried under natural sunlight, and then stored at (1.0 ± 0.5) ℃ and relative humidity of 90%–95% for 48 hours. Afterwards, the fruit were inoculated with Alternaria alternata and then kept under the same conditions. Sampling was conducted periodically to examine the effect of EBR treatment on postharvest black spot and reactive oxygen metabolism. The results showed that EBR treatment significantly increased the content of hydrogen peroxide (H2O2) shortly after inoculation (P < 0.05), continuously and significantly improved the activity of superoxide dismutase (SOD) and peroxidase (POD) over the entire culture period and significantly enhanced catalase (CAT) activity during the later stages (P < 0.05). In addition, it significantly inhibited the production rate of superoxide anion radical (O2-·), effectively reduced the content of malondialdehyde (MDA) as well as the increase in cell membrane permeability and the incidence of disease, and greatly inhibited the expansion of the lesion. Meanwhile, the results of transmission electron microscopy showed that EBR treatment could maintain the structural integrity of mitochondria, chloroplasts and other organelles in apricot fruit during storage. The mechanism behind the inhibition of the occurrence of postharvest black spot in apricots by EBR treatment may be closely related to regulating reactive oxygen metabolism and maintaining the structural integrity of organelles.

Key words: apricot fruit, 24-epibrassinolide, black spot disease, active oxygen metabolism