| Kiwifruit is not resistant to storage and easy to be rotten at room temperature after harvesting.Improving the storage resistance of kiwifruit is an important goal of kiwifruit breeding.The storage resistance is the internal factor that determines the storage period and shelf life of fruit.And varieties are the key factors affecting fruit storage life.Different varieties have large differences in storage resistance.Therefore,in this experiment,‘Xuxiang'?shorter storage life?and‘Hayward'?long storage life?with large storage differences were selected as test materials,comparing the postharvest physiology and internal differences between the two,providing a reference for the selection of new kiwifruit varieties with good quality and storage resistance.In order to provide the theoretical basis for the improvement of kiwifruit fresh-keeping technology,100?L·L-1concentration of ethylene and 0.5?L·L-1 concentration of 1-MCP were treated.The results showed that:1. The firmness of two varieties of'Xuxiang'and'Hayward'showed"S"decline during storage at 0?,and the difference in firmness was significant in the early storage period.The time for firmness of'Hayward'to drop to 10 N is 150 d,while'Xuxiang'is only95 d,whose storage time was 55 d shorter than'Hayward'.In the middle and later stage of storage,the weight loss rate of'Xuxiang'was significantly higher than that of'Hayward';2. During the whole storage period,the respiration rate and ethylene release rate of the two cultivars showed typical characteristics of the climacteric fruits.Compared with'Xuxiang','Hayward'not only delayed the emergence of respiratory peak and ethylene peak,but also significantly reduced ethylene release peak?'Xuxiang'was 3.5 times that of'Hayward'?;3. The content of starch,cellulose and propectin of'Hayward'were higher than that of 'Xuxiang',while the activities of amylase?AM?,cellulase?Cx?and cell wall enzymes?PG,PE,?-Gal?were lower than'Xuxiang',effectively delaying the softening of'Hayward'fruit;4. On the day of harvest,the epidermal cells of'Hayward'were more closely arranged,with more layers and thicker cuticle than those of'Xuxiang',On the contrary,during the storage process,the pulp cells of'Xuxiang',changed relatively much.By the end of the period,the cells have lost their fullness and are arranged irregularly,while the structure of the'Hayward'is relatively intact;5. The cell wall ultrastructure of pulp of the two varieties was similar on the day of harvest,showing a bright-dark-bright structure.However,in the middle stage of storage,the middle lamella of'Xuxiang'was completely degraded,and there was a gap in the cell wall structure,which was seriously damaged.During this period,the cell wall of'Hayward'did not change significantly.At the end of storage,the mitochondria ridge of'Xuxiang'disintegrated,the shape was disordered,and microfibrils around the cell wall were scattered,while the cell wall of'Hayward'degraded slowly,the overall structure is relatively complete;6. When treated with 100?L·L-1concentration of ethylene and 0.5?L·L-1concentration of 1-MCP,1-MCP could significantly slow the decline of fruit firmness,significantly reduce respiratory intensity and ethylene release rate,and inhibit the activity of polygalacturonase?PG?and pectin enzyme?PE?.Ethylene can significantly accelerate the softening of fruits,and promote respiration rate,ethylene release rate,and two enzyme activities,and these effects are more pronounced on'Xuxiang'.In summary,a comparative study of the physiological and tissue levels of two kiwifruit varieties with different storage resistance found that the storage resistance of fruit was not only related to the fruit tissue structure itself,but also closely related to starch degradation and cell wall polysaccharide degradation.Varieties with long storability,thick cuticle and epidermal cells,low weight loss rate,slow respiration rate and ethylene release rate,and low cell wall enzyme activity and'Xuxiang'is more sensitive to ethylene than'Hayward'. |
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