Effects of high temperatures on UV-B/visible irradiation induced postharvest anthocyanin accumulation in ‘Yunhongli No. 1’ (Pyrus pyrifolia Nakai) pears

Red Chinese sand pears (Pyrus pyrifolia Nakai) have seen increased cultivation in China in recent years, prized for their attractive market value and nutritional benefits. However, poor fruit coloration has been a noticeable problem. Postharvest ultraviolet-B (UV-B)/visible irradiation has been used to improve anthocyanin accumulation and thus the coloration of fruit skin in apple and other fruits. In this study, the efficacy of UV-B/visible irradiation was evaluated under high- (27 °C) and low-temperature (17 °C) conditions using red Chinese sand pear ‘Yunhongli No. 1’ as a model. The results showed that UV-B/visible irradiation was more effective in inducing anthocyanin synthesis in peel tissues and improving fruit coloration at 27 °C than at 17 °C. PAL activity was markedly higher at 27 °C than at 17 °C. Expression of PyMYB10 and five anthocyanin structural genes, PpPAL, PpCHI, PpCHS, PpF3H, and PpANS, was also higher in fruit irradiated at 27 °C than in fruit irradiated at 17 °C. For PpUFGT, transcription reached a maximum at 48 and 240 h after the onset of irratiation at 27 °C and 17 °C, respectively, but the peak value was lower at 27 °C than at 17 °C. There was no difference in expression of PpDFR between 17 °C and 27 °C irradiation temperatures. These results indicated that high temperatures (27 °C) enhanced UV-B/visible irradiation induced postharvest anthocyanin accumulation in ‘Yunhongli No. 1’ pears by up-regulating PyMYB10 and anthocyanin structural genes and increasing the activity of phenylalanine ammonia-lyase.

► Postharvest UV-B/visible irradiation induced anthocyanin accumulation in Chinese sand pear peels.
► Postharvest UV-B/visible irradiation induced red color development in Chinese sand pears.
► UV-B/visible applied at high temperature was more effective on red coloration in Chinese sand pears.
► UV-B/visible treatment up-regulated PyMYB10 gene expression.
► UV-B/visible treatment up-regulated expression of anthocyanin structural genes.