Inhibition of ethylene biosynthesis and associated gene expression by aminoethoxyvinylglycine and 1-methylcyclopropene and their consequences on eating quality and internal browning of ‘Starkrimson’ pears

Abstract

‘Starkrimson’ is a highly profitable red-skinned european pear (Pyrus communis) cultivar that has a short storage life due mainly to the development of a mealy texture upon ripening and an internal browning (IB) disorder during or after storage. In 2013, ‘Starkrimson’ pears were sprayed with aminoethoxyvinylglycine (AVG) at 0, 30, 60, and 120 mgL—1 1 week before harvest or treated with 1-methylcyclopropene (1-MCP) at 0. 3 µL·L—1 for 24 hours shortly after harvest, then stored at —1. 1 °C and evaluated over a 16-week period. The experiment was repeated in 2014. After 2 weeks of storage, control fruit (nontreated) had a higher respiration rate and ethylene biosynthesis than AVG or 1-MCP-treated fruit. Following 12 weeks of storage, control fruit exhibited a greater incidence of mealy texture and greater extractable juice (EJ) after ripening, and by 16 weeks significantly higher IB relative to AVG and 1-MCP-treated fruit. AVG at 30 mg·L—1 had little effect on any of the storage responses measured compared with control. AVG at 60 mg·L—1 reduced ethylene synthesis, respiration rate, and titratable acidity (TA) loss and maintained high eating quality with low EJ. Fruit treated with 60 mg L—1 AVG also developed markedly less IB following 16 weeks of storage than control or 30 mg·L—1 AVG treatments. AVG at 120 mg·L—1 did not improve storage quality achieved with 60 mg L—1 but delayed ripening capacity by 1 month. 1-MCP markedly inhibited ethylene synthesis and respiration rate and eliminated IB during 16 weeks of storage; however, 1-MCP-treated fruit required 14 days at 20 °C to ripen to high eating quality following 12 to 16 weeks of storage compared with 5 days for 60 mg—L—1 AVG. Both AVG and 1-MCP suppressed the expressions of ethylene synthesis (PcACSl, PcACS4, PcACS5, and PcACOl) and perception genes (PcETRl, PcETR2, and PcETR5) although 1-MCP was more efficient than AVG. In conclusion, preharvest AVG applications at 60 mg·L—1 or postharvest 1-MCP treatment at 0. 3 µL·L—1 extended storage life of ‘Starkrimson’; however, 1-MCP inhibited ripening capacity whereas 60 mg·L—1 AVG did not.