| The responses to postharvest methyl jasmonate (MeJA) and 1-methylcyclopronene (1-MCP) application in strawberry fruit were studied. We have examined the effects of MeJA and 1-MCP on fruit quality attributes, decay incidence and its relation to the induction of defensive responses during storage at 5℃. The results were as follows:1. Treatments with 1μmol/L MeJA effectively suppressed fruit decay, but had little effects on changes of flesh firmness, TA, TSS, total sugar, and vitamine C contents during storage. 100μmol/L MeJA promoted fruit decay incidence and declines of Vc and fruit firmness, but had little effect on other quality parameters. 10 and 50nL/L 1-MCP inhibited fruit decay, but had little effect on TA, TSS, total sugar and reducing sugar contents. 100 and 500nL/L 1-MCP maintained flesh firmness, but resulted in higher fruit decay and more loss of vitamine C and TSS.2. 1μmol/L MeJA significantly inhibited fruit decay, maintained higher levels of PAL, PPO, chitinase and β-1,3-glucanase activities and induced the accumulation of total phenolics. These results suggest that inhibition of fruit decay by MeJA was related to the induction of defense responses. The induced disease resistance may be involved in the mechanisms by which low concentration of MeJA inhibiting fruit decay. Fruits treated with 100μmol/L MeJA showed lower activities of PAL and PPO, and less total phenolics after days 6 than the control fruit. The disadvantageous effects of MeJA on enhancing fruit decay may be ascribed to the impaired natural defense responses in fruits.3. 1μmol/L MeJA significantly inhibited decay incidence and the increases in ethylene production, superoxide radical, H2O2 and MDA contents, maintained higher levels of SOD, CAT and APX activities. 100μmol/L MeJA significantly promoted decay incidence and the increases in H2O2 and MDA contents, resulted lower CAT and APX activities. These results indicate that the 1μmol/L MeJA may maintain the balance of active oxygen metabolism, thereby delaying fruit senescence and inhibiting fruit decay, whereas 100μ mol/L MeJA destroyed this balance and promotd the decay incidence in strawberry fruit.4. 500nL/L 1-MCP significantly suppressed PAL activity and the changes of total phenolics, anthocyanin and carotonoid, inhibited the increases in ethylene production. As a result, 500nL/L 1-MCP reduced fruit antioxidant potential and promoted decay incidence. Thus enhancement of fruit decay by 500nL/L 1-MCP was related to the reduction of diseases resistance and antioxidant potential in strawberry fruits. |
