Low temperature conditioning alleviates peel browning by modulating energy and lipid metabolisms of 'Nanguo' pears during shelf life after cold storage

Refrigeration is a common technique for impeding the postharvest ripening of the 'Nanguo' pear (Pyrus ussuriensis Maxim.). However, peel of pears gradually become brown when the fruit are returned to room temperature after cold storage. Low temperature conditioning (LTC), in which fruit were initially stored at 10 °C and then cooled during a 20 day period, delayed the incidence of peel browning (PB) of pears in our study. LTC-treated fruit showed a decrease in the content of malondialdehyde (MDA) and the relative leakage rate of the peel. The ATP content and energy charge (EC) were higher in LTC-treated pears. Gene expression levels of transcripts for NADH dehydrogenase (NDA), ATP synthase (ATPase) and vacuolar proton-inorganic pyrophosphatase (VPP), which were involved in oxidative phosphorylation, were all up-regulated by LTC treatment. Gene expression levels of phospholipase D (PLD) involved in glycerophospholipid metabolism were lower in LTC-treated fruit during the shelf-life. These results indicate that LTC treatment can effectively alleviate the PB of 'Nanguo' pear and the possible mechanisms are discussed.