| Exogenous melatonin treatment was applied on the pre-veraison and post-harvest ‘Shine Muscat’ grape berries to determine the effects of treatment concentrations and types on quality of table and storage quality.The main research results were as follows.1.Exogenous melatonin treatment by soaking fruits and watering roots significantly improved the table quality of grape.Compared to the control,melatonin treatment promoted berry flavor via significantly increasing the content of soluble solids,glucose and fructose and decreasing the content of titratable acid,malic acid and tartaric acid.As regards berry texture,melatonin enhanced skin hardness,frangibility,toughness and flesh hardness of grape berries.Besides,melatonin increased berry size and weight.2.In the study,two concentrations(5 μM and 50 μM)and two treatment methods(soaking fruits and watering roots),were used to treat grape at the pre-veraison stage.Principal component analysis was performed using the quality parameters.The load diagrams composed of principal components 1 and 2 showed that the values from the same concentration and two different treatment types were in the same quadrant,indicating the similar effects of two treatment types with the same treatment concentration on berry quality.Therefore,the effect of melatonin treatment at pre-verasion on berry quality is mainly determined by the concentration of applied melatonin rather than the treatment method.3.Melatonin treatment and especially melatonin plus low temperature at postharvest stage significantly increased the melatonin content of berries,slowed down the deterioration rate of quality,and improved the storage quality.Under low-temperature conditions,melatonin treatment of post-harvest fruits slowed the browning rate of berry peduncle and delayed the occurrence of ethylene release peak in peduncle.Under room temperature and low temperature environment,melatonin treatment reduced the weight loss rate,decay rate and horizontal and vertical diameter reduction rate,and enhanced the healthy fruit rate,flesh hardness and content of the phenols.The role of melatonin in regulating the content of sugar and acid was affected by the storage temperature.Compared with the control,melatonin significantly increased sugar and acid under room temperature,however the increment in sugar content was reduced and acid content did not change significantly when subjected to low temperature.4.Melatonin treatment can significantly increased the content of the total aroma and the characteristic aroma of berries,such as(E)-2-hexenal,hexenal,linalool and2,4-ditert-butylphenol.At verasion,the treatment of watering 5 μM melatonin significantly increased alcohols and terpenes,while 50 μM treatment significantly increased aldehydes.For postharvest treatment,the total aroma content increased significantly and then gradually decreased under the room temperature.In the low temperature environment,melatonin treatment increased the content of total aroma and characteristic aroma,and delayed the decline of total aroma and characteristic aroma.Compared with in the treatment under room temperature environment,the treatment under low temperature led to great increase of berry aroma and generated robust effects. |
