Molecular Physiological Mechanism Of Coloration Induced And Regulation Of Red Chinese Sand Pears(Pyrus Pyrifolia Nakai)

Red Chinese sand pears (Pyrus prifolia Nakai) native to Yunnan Province and southern part of Sichuan Province, Recently, with extensive cultivation of red Chinese sand pear cultivars newly released by hybrid breeding in China, the pears had been widely accepted by consumers, and are expected to be of value of Chinese production in the future. Poor fruit coloration has been a noticeable problem, however, there are short of the technique of coloration regulation on production. To date, little studies have been carried on coloration regulation of red Chinese sand pears on scientific research. What’s more, Chinese sand pears and European pears(P. communis L.) differ considerably in pigmentation pattern. Therefore, an investigation of molecular physiological mechanism of coloration regulation of red Chinese sand pears need to be done, to improve the coloration of red Chinese sand pears. Three red Chinese sand pear cultivars,’Meirensu’(mid-maturing),’Mantianhong’(mid-maturing) and ’Yunhongli No.l’(late-maturing) were used as materials in this study. Color response and related molecular physiological mechanism of coloration regulation of red Chinese sand pears to post-harvest induced is influenced by temperature, light, maturity, wounded, chemicals was investigated systematically. The main results are as follows:The efficacy of UV-B/visible irradiation was evaluated under high-(27℃) and low-temperature (17℃) 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 at27℃than at17℃. PAL activity was markedly higher at27℃than at17℃. Expression of PyMYB10and five anthocyanin structural genes, PpPAL, PpCHI, PpCHS, PpF3H, and PpANS, were also higher in fruit irradiated at27℃than in fruit irradiated at17℃. For PpUFGT, transcription reached a maximum at48and240hours after the onset of irratiation at27℃and17℃, respetively, but the peak value was lower at27℃than at 17℃. These results indicated that high temperatures (27℃) enhanced UV-B/visible irradiation induced postharvest anthocyanin accumulation in’Yunhongli No.1’pears by up-regulating PyMYB10and anthocyanin structural genes and increasing the activity of phenylalanine ammonia-lyase.Color response of red Chinese sand pears to different temperatures treatment similar to’Gala’ apple (Malus domestic Borkh), but differ considerably to European pears under postharvest artificial irradiation conditions. The optimum temperature of ’Mantianhong; and’Meirensu’was17℃and12℃, respectively. Light intensity (quantity) and light wavelength (quality) are important factors affecting anthocyanin synthesis in red Chinese sand pears. Higher light intensity was good for anthocyanin synthesis in red Chinese sand pears. Simultaneous irradiation with UV-B and white light had a synergistic effect. Based on the current results, we suggested that low temperature and high light intensity was good for red color development and obtaining fruit quality of’Mantianhong’and’Meirensu’Wounded treatments decreased fruit firmness, increased ethylene production rate of fruit, enhanced post-harvest anthocyanin accumulation in injured part of red Chinese sand pears, and up-regulated the transcription level of anthocyanin biosynthetic related genes:PpF3H, PpANS, PpUFGT and PyMYB10, markedly. Ethylene production of control fruit was under the detection limit, and only a trace amount of anthocyanin was detected in control fruit. Results above indicated that ethylene might be involved in the regulation of anthocyanin accumulation in red Chinese sand pear, and improve the level of anthocyanin accumulation in red Chinese sand pear. It was suggested that wounded treatments could be used as a mean to better understand the regulation mechanism of anthocyanin biosynthesis in fruits.Color response of’Mantianhong’pears to postharvest UV-B irradiation was affected by fruit maturity, and the effect of maturity on accumulation of anthocyanin became smaller near the commercial harvesting period. Higher accumulation of anthocyanin in mature fruits than in immature fruits resulted from significant increase of the anthocyanin structural and regulatory genes, especially for PpCHS, PpF3H, PpANS, PpUFGT, PyMYB10and PpbHLH in red Chinese sand pears. Based on the results above, we suggested that10DBH harvest was the optimal maturity for UV-B-Induced post-harvest anthocyanin accumulation of red Chinese sand pear.Different chemicals has different efficiency in coloration induced and fruit quality regulating. No positive efficiency was observed in0.4m mol·L-1ABA and3m mol·L-1GA treatment in inducing anthocyanin accumulation of’Mantianhong’. However, alone2m mol·L-1ETH,0.12m mol· L-1GNT,2m mol·L-1MJ and mixture of these chemicals enhanced anthocyanin accumulation in red Chinese sand pear. Simultaneous irradiation with MJ and ETH had a synergistic effect in inducing anthocyanin accumulation of’Mantianhong’. All these treatments can obtain fruit quality of’Mantianhong’pear, such as fruit firmness, TSS, soluble sugar and organic acid.MJ treatment enhanced anthocyanin accumulation in peel of’Mantianhong’pear by up-regulating the transcription level of anthocyanin biosynthetic related genes: PpCHS2, PpCHI3, PpF3H, PpANS, PpDFRl, PpUFGT1PpUFGT2and PyMYB10O, markedly. After irradiation, PpbHLH and PpWD40were up-regulated in MJ treatment, but not in control. We suggested that higher transcription level of PpbHLH and PpWD40in MJ treatment than control is one of the reasons of enhancing anthocyanin accumulation in peel of’Mantianhong’pear. During anthocyanin accumulation of red Chinese sand pear, the transcription level of different anthocyanin structural gene family members was significantly different, and we presumed that the function of these genes was different.