Inhibition of Ethylene Biosynthesis and Perception by 1-Methylcyclopropene and Its Consequences on Chlorophyll Catabolism and Storage Quality of ‘Bosc’ Pears

Bosc is a winter cultivar of european pear (Pyrus communis) that has a relatively short storage life partially due to a high ethylene production rate (EPR) during cold storage. ‘Bosc’ pears were harvested at commercial maturity and treated with gas 1-methylcyclopropene (1-MCP) at 0, 0.15, and 0.3 µL·L−1 and stored at −1.1 °C for 8 months. Results indicated that all 1-MCP treatments inhibited EPR and respiration rate (RR), retarded the degradation of chlorophyll and titratable acidity (TA), and extended storage quality; but inhibited ripening capacity. 1-MCP at 0.15 and 0.3 µL·L−1 had the same efficacy on keeping fruit quality although its higher rate was more efficient on inhibiting EPR and RR. The expression of ethylene synthesis genes (PcACS1, PcACS2, PcACS4, PcACS5, and PcACO1) and receptor genes (PcETR1, PcETR2, and PcERS1) was upregulated in control fruit during storage and they were downregulated significantly by 1-MCP treatments. In contrast, the ethylene receptor genes of PcETR5 and PcCTR1 were downregulated in control fruit during storage and were unaffected by 1-MCP treatments. Although the transcription levels of chlorophyll degradation genes PcPPH, PcNOL, PcSGR, PcRCCR, PcNYC, and PcPAO were all upregulated in control fruit during storage and downregulated by 1-MCP; only PcCHL was downregulated in the control and 1-MCP had no consistent effect on it. The relationship of ethylene biosynthesis/perception with chlorophyll degradation and storage quality in european pears was discussed.