Effects of ethylene and 1-methylcyclopropene on the postharvest qualities of 'Shamouti' oranges

Citrus fruits are nonclimacteric and produce only low amounts of ethylene. However, exogenous applied, and possibly endogenous ethylene, may be involv ed in the regulation of fruit maturation and senescence. We examined the ef fects of ethylene and 1-methylcyclopropene (1-MCP), an ethylene action inhi bitor, on the postharvest qualities of 'Shamouti' (Citrus sinensis L. Osbec k) oranges. Neither ethylene nor 1-MCP had any effects on the loss of fruit weight and firmness. However, ethylene had disadvantageous effects on most other postharvest parameters. It increased the appearance of chilling inju ry (CI) symptoms, stem-end rot decay, and the content of volatile off-flavo urs in the juice head space and fruit internal atmosphere. The only protect ive effect of ethylene during postharvest storage was in reducing the amoun t of decay caused by mold rots. 1-MCP treatment effectively inhibited the e thylene effects on 'Shamouti' oranges, as indicated by blocking of the degr eening process, but was ineffective in restoring the negative effects of et hylene during storage; it even weakened the tissue and increased CI symptom s, decay development, and the accumulation of volatile off-flavours. It is concluded that while high concentrations of exogenous applied ethylene are undesirable during storage, and enhance fruit deterioration, the small amou nts of endogenous ethylene produced by the fruits may be required to mainta in their natural resistance against various environmental and pathological stresses. In future, we suggest that 1-MCP may be applied as a postharvest treatment to inhibit the degreening process in citrus fruits which are pref erably marketed green, but special care must be taken to avoid CI and decay development. (C) 1999 Elsevier Science B.V. All rights reserved.