Study On1-MCP And Meja Regulation And Mechanism Of Quality Of Hami Melon Fruit After Harvest

Hami melon is an important native and famous fruit representing an especial variety of xinjiang, which with fragrant aroma, fleshy and juicy known by the world and liked deeply by consumer. Hami melon has an important position of the horticultural industry in xinjiang. There are many varieties of hami melon that are cultivated in widespread area in xinjiang. Most of the fruit are transported to be selled at mainland china and exported to foreign region. After harvest, the fruit rapidly change senescence and the quality turn bad due to the high temperature and long distance transportion at ambient temperature. Hami melon fruit are susceptible to decay and have short shelf life under aging of fruit condition. Low temperature storage was commonly used to delay quality deterioration and extend storage periods of hami melon fruit,but it leads the occurrence of chilling injury to induce severe rot of fruit. The decay of hami melon fruit brought to enormous losses during postharvest storage and transpitation, it became a key obstruction to block the fine development of hami melon industry. It is crucial to study the regulation and control technology of delaying fruit deterioration and aging, control chilling injury,reduce decay of hami melon fruit after harvest for transportation and storage. In this paper, hami melon fruit (.Cucumis melo L. ssp.melon Pang) were used as research materials to study the effect1-methylcyclopropene and methyl jasmonate on physiological aging and chilling injury, postharvest major fungal disease of hami melons fruit and involved the possible mechanism. The research results were as follows:1. Hami melon fruit were pre-treated with different concentrations of1-MCP for24h and then stored at25℃to investigate the effect of1-MCP treatment on quality parameters and physilogy,volatility aroma and decay. The results showed that1and5μl/L1-MCP treatment maintained the higher level of the soluble solide content (SSC), suppressed the reduction of pericarp chloophyll, delayed the decline of vitamin C content of hami melon fruit during storage.1and5μl/L1-MCP treatment inhibited the respiration rate, delayed the appearance of respiration climacteric peak, declined the ethyleng production rate, suppressed the decrease of firmness, reduced the ion leakage, postponed the beginng of decay and reduced decay index and rate of melon fruit. The production of volatile aroma were significantly suppressed, the kind and concentration of volatile aroma compounds of melon fruit were markedly reduced, especially at content of ester and alcohol of of ripeness fruit treated with1μl/Ll-MCP, which had relevance to the ripen of fruit delayed by1-MCP. The quality parameters and physiology senescence of hami melon fruit treated with1and5μl/L1-MCP were no marked difference, therefore, we choosed the1μ1/L1-MCP for follow researchs.2. The effect of1μl/L1-MCP treatment on the cell walls hydrolytic enzyme activity and the cell walls component of hami melon fruit were" investigated. The increasing of PG, PME, EGase and β-GAL activity were inhibited by treated with1-MCP, meanwhile, the decline of content of pectin solubled in CDTA and firmness of melon fruit were delayed. The β-GAL playes an important role in disassembling cell wall due to that the rapid rise of β-GAL activity were consistent with the drop of frimness of control hami melon fruit.1-MCP treatment inhibited the increasing of ACS and ACO activity, reduced the ACC content, delayed the ripening of hami melon fruit. Possibly, ACO played a key role at step of ethylene synthesis process in hami melon because that ethylene production was suppressed by lower ACO activity in fruit treated by1-MCP.3. The effect of1μL/L1-MCP on the relation between fruit ageing and active oxygen detoxifying enzymes and the mechanism of ROS metabolise and fruit ageing were investagated.1-MCP treatment inhibited remarkably decrease of firmness, delayed the reduction of chlorophyll decompose and maintained higher SSC content and good fruit quality.1-MCP treatment inhibited remarkably the respiration rate, delayed the apperance of respiration peak, reduced the ethylene production rate of fruit during storage. The activities of SOD, CAT and POD in hami melon fruit were supressed significantly by1-MCP treatment. Meanwhile, the accumulation of O2-and the content of MDA were declined. The fruit ageing was delayed due to rmaintain the balance of ROS metabolime and reduceing membrane oxidation.4. The effect of different concentrations MeJA treatment on quality and the metabolism of ethylene of postharvest hami melon fruit were investegated.10μmol/L MeJA treatment could postpone the decreasing of firmness, maintained higher SSC and vitamin C content of fruit during storage. The chilling injury of hami melon fruit treated MeJA was reduced and good quality of fruit was maintained during storage. The MeJA-treated-fruit of the respiration rate and ethylene production rate were inhibited. MeJA treatment enhanced the activities of ACS and ACC content, reducede the activity of ACO in hami melon fruit.5. The effect of10μmol/L MeJA treatment on chilling injury of hami melon fruit during cold storage and the metabolism of ROS were investigated.10μmol/L MeJA treatment reduced chilling index, increased the activities of activity oxygen detoxifying enaymes POD,SOD,CAT and APX of melon fruit during cold storage. The increasing of accumulation of O2-、H2O2and the content MDA were restrained by MeJA treatment.Fruit-treated with MeJA had integrality cell membrane.6. The effect of different concentrations MeJA on the germination of spores, extention of hypha and spot diameter of melon inoculated with A.alternata and F.semitectum at ambient temperature were investigated.10μmol/L MeJA reduced the rate of germination and the spread of hypha of A.alternata and F.semitectum on PDA at25℃.The spot diameter of fruit treated with10μmol/L MeJA inoculated with A.alternata and F.semitectum were inhibited. MeJA could enhance the activities of POD and SOD, delay the decline of the activity of CAT in hami melon fruit. The disease resistance in hami melon fruit treated with10μmol/L MeJA was induced because of increasing the activitise of chitnase and β-1,3-glucanase.