|MA, YURONG - Shandong Agricultural University|
|YANG, MENGNAN - Shandong Agricultural University|
|WANG, JINGJING - Shandong Agricultural University|
|WANG, QINGGUO - Shandong Agricultural University|
Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2016
Publication Date: 1/18/2017
Citation: Ma, Y., Yang, M., Wang, J., Jiang, C., Wang, Q. 2017. Application of exogenous ethylene inhibits postharvest peel browning of ‘Huangguan’ pear. Frontiers in Plant Science. 7:2029. doi:10.3389/fpls.2016.02029.
Interpretive Summary: Huangguan pear (Pyros bretsschneideri Rehd cv. Huangguan) is a new cultivar with comprehensive qualities and widely planted in northern China. However, a surface brown disorder in the peel often occurs before harvest or during early stage of storage. Symptom in the affected area of the peel is lightly brown at first, and then becomes darker as the disorder progresses. The disorder usually only affects the peel of fruits but not the flesh. However, the surface brown disorder often seriously impacts on the exterior quality of ‘Huangguan’ pear and causes enormous economic loss. Browning disorder of pears is affected by both preharvest factors (such as picking date, maturity, fruit size and kind of fruit-bags) and postharvest factors (such as the duration of cooling period, the storage temperature and the CO2 and O2 concentrations). Peel browning of fruits appears to be related to the damage of membrane integrity. The antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and peroxidase (POD) are believed participating in the browning of fruits and vegetables. These enzymes could protect the integrity of membrane from damage by scavenging H2O2, superoxide and other free radicals. Dipping with CaCl2 and pullulan reduced the incidence of brown spots of ‘Huangguan’ pear by decreasing the activity of PPO and POD and increasing the activity of CAT and SOD. Application of pure oxygen induced the antioxidant enzymes (SOD, APX and CAT) activity in lichi fruit, thereby maintained the membrane integrity and inhibited the pericarp browning. A number of different approaches such as slow cooling, methyl jasmonate, cold conditioning, 1-MCP and CaCl2 are being tried to reduce the incidence of peel browning of pears. Methyl jasmonate can effectively inhibit the peel browning of ‘Huangguan’ pear when cooled rapidly. A cold-conditioning at appropriate temperature (8-9') before cold storage (0') significantly inhibited the peel and core browning as well as reduced the accumulation of ethanol during storage and shelf life, maintained the high edible quality of ‘Huangguan’ pear. Compared with control, treatments with 1-MCP, CaCl2 and 1-MCP + CaCl2 dramatically reduced the skin browning of ‘Huanguan’ pear. Moreover, 1-MCP could delay the ripening of ‘Huangguan’ pear, prolong the storage life, and maintain the fruit quality and palatability. Though different methods have been applied for inhibiting the peel browning of ‘Huangguan’ pear, there are numerous issues associating with the approaches, such as time-consuming, higher cost, safety and the stability of the efficiency. For example, slow cooling is commercially applied for the inhibition of peel browning. However, this cooling process is time-consuming, which goes against keeping the fruit quality. Moreover, after slow cooling, fruits showed a higher rot rate and withered stalk rate. Thereby, developing a rapid, efficient and safe way to protect ‘Huangguan’ pear from skin browning is urgent and essential. As a plant hormone, ethylene is believed to be responsible for the ripening and senescence of fruits and vegetables after harvest. However, some positive effects of ethylene on maintaining the quality of fruits are also reported. Ethylene plays important roles in protecting plants from various stresses. Zhou et al. found that the presence of ethylene during cold storage alleviated the woolliness of nectarines, a chilling injury phenomenon. Besides, ethylene conditioning at 12' extended the shelf life of chilling injury sensitive and non-chilling peel pitting (NCPP) sensitive oranges. Moreover, ethylene conditioning prevented the initial decrease in flavonoid content and reduced the calyx abscission and NCPP. Although application of ethylene treatment has been well documented in various fruits, the effect of ethylene on the browning and antioxidant capa
Technical Abstract: Peel browning disorder has an enormous impact on the exterior quality of ‘Huangguan’ pear whereas the underlying mechanism is still unclear. In this study, the effect of exogenous ethylene on peel browning of pear fruits stored at 0' was evaluated. Results showed that ethylene effectively inhibited the peel browning, decreased the electrolyte leakage and respiration rate, delayed the loss of total phenolic compounds. Ethylene (5 µL/L) treatment also significantly enhanced the activity of catalase (CAT), ascorbate peroxidase (APX) and superoxide dismutase (SOD) and increased the DPPH inhibition rate, whereas inhibited the activity of polyphenol oxidase (PPO) and peroxidase (POD). Our data revealed that ethylene prevented the peel browning through improving antioxidant enzymes (CAT, APX and SOD) activities and reducing the PPO activity, electrolyte leakage rate and respiration rate. This study demonstrated that exogenous ethylene application may provide a safe and effective alternative method for controlling browning and contributed to the understanding of peal browning of ‘Huangguan’ pear.