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In order to prolong the storage period of ‘Huangguan’ pear and reduce the deterioration of fruit quality during long-term storage and subsequent shelf life, this study conducted preharvest treatment with different concentrations of aminoethoxyvinylglycine (AVG) to ‘Huangguan’ pear. Before and after refrigeration for 180 days and after subsequent shelf life for 7 days, quality indicators were tested. The results showed that compared with the control group, preharvest AVG treatment delayed the decline of fruit firmness, maintained higher contents of soluble solids and titratable acids, and effectively inhibited fruit surface browning and core browning, the most pronounced effect being observed at 200 mg/L AVG. During long-term cold storage, the contents of arbutin, chlorogenic acid and total phenols increased with the occurrence of core browning, and the activity of polyphenol oxidase (PPO) increased. The expression levels of PbPAL1, PbPAL2, PbPPO1, PbPPO5, PbLOX1 and PbLOX5 were up-regulated during cold storage, but down-regulated during shelf life. Preharvest treatment with 200 mg/L AVG significantly reduced the consumption of arbutin, chlorogenic acid and total phenols, inhibited the increase of PPO activity along with the expression of PbPAL1, PbPAL2, PbPPO1, PbPPO5 and PbLOX5, and thus effectively reduced core browning in ‘Huangguan’ pear .

'Huangguan' pear (Pyrus bretschneideri Rehd. cv. Huangguan) is a widely planted cultivar in China. However, it is susceptible to core browning after harvest. In this study, aminoethoxyvinylglycine (AVG) was applied at 200 mg L−1 one and two weeks prior to harvest, and its effects on fruit quality, ripening and core browning were investigated during fruit storage at ambient temperature (25 ± 1 °C). The results showed that there was higher firmness, soluble solids content (SSC) and titratable acid (TA) content, but a lower ethylene production rate and core browning index in AVG-treated fruit than in control (water). Compared with the control fruit, AVG treatment decreased the malondialdehyde (MDA) content and polyphenol oxidase (PPO) activity, delayed the peak of chlorogenic acid (CGA) content in the core tissue, and significantly inhibited the expression of genes such as ACC synthase (PbACS2, PbACS3a, PbACS5a and PbASC5b), ACC oxidase (PbACO1 and PbACO2), ethylene receptors (PbETR2 and PbERS1), ethylene response factor (PbERF1), phenylalanine ammonia lyase (PbPAL1), cinnamate 4-hydroxylase (PbC4H4), 4-hydroxycinnamoyl- CoA ligase (Pb4CL2), hydroxycinnamoyl- CoA shikimate hydroxycinnamoyl transferase (PbHCT1 and PbHCT3), and polyphenol oxidase (PbPPO1 and PbPPO5), as well as phospholipase D (PbPLD) and lipoxygenase (PbLOX1 and PbLOX5). Thus, these results suggested that the reduction in core browning by preharvest application of AVG might be due to an inhibitory effect on the expression of genes associated with ethylene biosynthesis and signaling pathways, CGA biosynthesis, PPO and cell membrane degradation in 'Huangguan' pear. [ABSTRACT FROM AUTHOR]

Superficial scald is a postharvest physiological disorder that occurs in pear during and after cold storage. In this study, the superficial scald index; α-farnesene and its oxidation products, conjugated trienols (CTols); phenolic content; and the expression of its related genes were investigated in two different pear cultivars, 'Wujiuxiang' (Pyrus communis L.) and 'Yali' (Pyrus bretschneideri R.), following 115 days of cold storage at 0 °C followed by 7 days of shelf life at 20 °C. The results indicated that the superficial scald occurred after 115 days of cold storage and became more severe during the shelf life of the 'Wujiuxiang' pear, whereas no scald was observed in 'Yali'. The α-farnesene levels increased rapidly at first and then decreased, while the CTols contents increased significantly in 'Wujiuxiang' as compared to 'Yali', and the expression levels of the genes involved in α-farnesene and CTols metabolism (HMGR1, HMGR2, GSTU7, GPX5, and GPX6), as well as the phenolic synthesis (PAL1, PAL2, C4H1, 4CL2, C3H, and ANR) of the peel, were significantly up-regulated at the onset of the superficial scald. In addition, the relative conductivity and contents of catechin and epicatechin were higher, and the expression level of the laccase gene (LAC7) significantly increased with the development of superficial scald, while lower contents of chlorogenic acid, arbutin, and isorhamnetin-3-3-glucoside, as well as the lower expression levels of a phenolic-synthesis-related gene (C4H3) and polyphenol oxidase genes (PPO1 and PPO5), were noticed in 'Wujiuxiang' as compared to 'Yali'. The results indicated that the onset and progression of superficial scald were associated with the accumulation of CTols, cell membrane breakdown, and higher catechin, epicatechin, and rutin contents, as well as the expression of associated genes of the peels of pear fruit. [ABSTRACT FROM AUTHOR]

Highlights • 1-MCP effectively maintained the fruit quality of 'Yali' pear under cold storage. • 1-MCP decreased H 2 O 2 content in the core of 'Yali' pear. • 1-MCP maintained higher levels of AsA and GSH in the core. • 1-MCP reduced phenolics content and PPO activity in the core. • 1-MCP markedly inhibited the expression of PbPPO1 and PbPPO5. Abstract 'Yali' pear (Pyrus bretschneideri Rehd. cv. Yali) is susceptible to core browning after a long term of cold storage. In this study, the effects of 1-methylcyclopropene (1-MCP) with different concentrations (0, 0.25, 0.5, 1.0 μL L−1) on the quality and core browning of 'Yali' pear fruit were investigated. The results showed that 1-MCP significantly reduced the ethylene production, kept higher firmness and titratable acidity (TA) content, and lowered core browning. Moreover, the most effective concentration of 1-MCP was found at 1.0 μL L−1. Compared with control, 1.0 μL L−1 1-MCP treatment decreased the content of H 2 O 2 , while maintained higher levels of ascorbic acid (AsA) and glutathione (GSH) of core, and meanwhile, it reduced phenolics content and polyphenol oxidase (PPO) activity of core. In addition, among the four encoded the enzyme of PPO genes (PbPPO1 , PbPPO4 , PbPPO5 and PbPPO6), the expressions of PbPPO1 and PbPPO5 were markedly inhibited by 1-MCP. It suggested that 1-MCP could effectively keep fruit quality, and inhibit core browning which was resulted from the inhibition on accumulation of reactive oxygen species, reduction on phenolics content, PPO activity and its associated genes (PbPPO1 and PbPPO5) expression of core in 'Yali' pear during cold storage. [ABSTRACT FROM AUTHOR]