Effects Of Postharvest Active Oxygen And Ethylene Metabolism Of Table Grapes On Browning Of Fruit Rachis

Xinjiang’s grape planting area and output rank are first in the country.The grapes are tender,juicy,delicious,and nutritious,which are deeply loved by consumers at home and abroad.However,in the process of storage and transportation,the quality of table grape is easily deteriorated due to the browning of the rachis,which seriously restricts the export sales of table grape.Therefore,Xinjiang Red Globe and Munage grape were used as the test materies.Explored the regulation mode of ACC oxidase（ACO）and ACC synthase（ACS）family genes on fruit rachis brown.It will be hoped to provide a theoretical reference for the research on the preservation of grapes after harvest.The main findings are as follows:（1）The correlation between grape varieties and rachis browning and storability were compared.The issue water content and chlorophyll content were higher than Munage grape rachis.The activities of Polyphenol Oxidase（PPO）and Phenylalanine Ammonia-Lyase（PAL）activities were low,inhibited the synthesis of total phenols and flavonoids,resulted in slow browning of the rachis and better storage.The browning index of grape rachis was significantly negatively correlated with tissue water content and chlorophyll content（P<0.01）,total phenols,flavonoids,and PPO activities were positively correlated（P<0.05）.Rachis browning index of Red Globe grapes was extremely significantly negatively correlated with Peroxidase（POD）（P<0.01）.Rachis browning index of Munage grapes was negatively correlated with PAL（P<0.01）.Possibly due to the differences in species,the content of total phenols and flavonoids is different,resulting in different POD and PAL activities.It can be seen that POD may be the main cause of browning of Red Globe grape rachis,and PAL is the main cause of browning of Munage grapes rachis.（2）The effect of active oxygen metabolism on the browning of fruit rachis was analyzed.The relative conductivity of Munage grape rachis and the content of malondialdehyde（MDA）were higher than that of Red Globe grape,the degree of cell structure damage and membrane lipid peroxidation are greater.The activities of Superoxide dismutase（SOD）,Catalase（CAT）and Ascorbate peroxidase（APX）promotes the accumulation of Superoxide anion free radical（O₂^-·）,Hydrogen peroxide(H₂O₂)content,thereby enhancing the browning of fruit rachis.（3）The effect of ethylene metabolism on the browning of grape rachis was studied.The 1-MCP was used to treat the Red Globe grape and Munage grape rachis.It showed that ethylene accelerates the color change of grape rachis and enhanced the browning of the rachis by promoting the content of1-aminocyclopropane-carboxylic（ACC）,increasing the activities of ACO and ACS enzymes.（4）The influence of ACO and ACS family gene expression on grape rachis browning were discussed.In the grape genome,there are 3 ACO genes and 9 ACS genes.The experiment found that the relative expression of ACO and ACS family genes is slightly different in different grape varieties.The expression level of Vv ACO1 in the rachis of Red Globe grapes was higher,and Vv ACO2 was lower.Ethylene could induce the up-regulation of Vv ACS3,Vv ACS4 and Vv ACS5 in the rachis of Red Globe grapes,it induced the up-regulated expression of Vv ACS8 gene and Vv ACS9 in the Munage grape rachis.Therefore,Vv ACO1,Vv ACS3,Vv ACS4,and Vv ACS5 may play a major role in the browning of Red Globe grape rachis.Vv ACS8and Vv ACS9 jointly determine the browning of Munage grape rachis.