Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2011
Publication Date: 1/1/2012
Citation: Zhang, D., Yu, B., Bai, J., Qian, M., Shu, Q., Su, J., Teng, Y. 2012. Effects of high temperatures on UV-B/visible irradiation induced postharvest anthocyanin accumulation in ‘Yunhongli No. 1’ (Pyrus pyrifolia Nakai) pears. Scientia Horticulturae. 134:53-59. Interpretive Summary: Postharvest application of ultraviolet-B (UV-B)/visible irradiation improved red color development of Chinese sand pear fruit. It was more effective when the irradiation was applied at 27C than at 17C. Contents of anthocyanin, a group of pigment compounds which are responsible for the red, purple, and blue colors of fruit, changed parallel to grade of the redness in the fruit skin. The likely mechanism is that UV-B/visible irradiation stimulated genes responsible for anthocyanins, and an enzyme needed to produce anthocyanins.
Technical Abstract: 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- (27C) and low-temperature (17C) 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 27C than at 17C. PAL activity was markedly higher at 27C than at 17C. Expression of PyMYB10 and five anthocyanin structural genes, PpPAL, PpCHI, PpCHS, PpF3H, and PpANS, was also higher in fruit irradiated at 27C than in fruit irradiated at 17C. For PpUFGT, transcription reached a maximum at 48 and 240 h after the onset of irratiation at 27C and 17C, respectively, but the peak value was lower at 27C than at 17C. There was no difference in expression of PpDFR between 17C and 27C irradiation temperatures. These results indicated that high temperatures (27C) 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.