Application Of Sodium Nitroprusside In Regulating Postharvest Strawberry Fruit Softening And Ellagic Acid Metabolism

Strawberry fruit is rich in nutrients,tender and juicy,and has a strong aroma.It is favored by consumers and has a huge market value in China.However,the strawberry fruit has thin skin,is susceptible to mechanical damage,and is not resistant to storage and transportation,which greatly shortens the shelf life of strawberries.Therefore,there is an urgent need to find a safe and effective treatment method.Sodium nitroprusside（SNP）is one of the exogenous NO donors,which plays an important role in maintaining fruit quality and plant stress resistance.In this paper,"Tianbao" strawberry fruit was used as the experimental material,and SNP(0,1,5,10 μmol·L^-1)solutions with different concentrations were used for soaking treatment,and the optimal concentration was screened out,to explore the effects of SNP on postharvest strawberry fruit quality,cell wall metabolism and ellagic acid metabolism,the results are as follows:（1）Compared with the control treatment and other treatments with different concentrations,5 μmol·L^-1 SNP treatment effectively inhibited the increase of strawberry fruit respiration rate and relative electrical conductivity,and slowed down the nutrient substances caused by the fruit’s respiration and transpiration.The consumption and water loss of strawberries delayed the increase of strawberry fruit weight loss rate and better maintained the fruit firmness.At the same time,5 μmol·L^-1 SNP treatment effectively maintained the content of soluble solids in strawberry fruit,inhibited the increase of color difference value,slowed down the browning of fruit,and maintained the quality of strawberry fruit after harvest.（2）5 μmol·L^-1 SNP treatment inhibited the activities of polygalacturonase（PG）,cellulase（Cx）,β-glucosidase（β-Glu）,and xyloglucan endotransglycosylase（XET）,pectin methylesterase（PME）,β-galactosidase（β-Gal）in strawberry fruit,which slowed down the decomposition of cell wall polysaccharides,delayed the hydrolysis of CDTA-type pectin and Na2CO3-type pectin and the conversion to water-soluble pectin,efficient maintenance of cellulose and hemicellulose content.The results showed that SNP treatment could inhibit theactivity of cell wall metabolism-related enzymes,maintain the content of cell wall substances,maintain the cohesion of the cell wall during the fruit ripening process,and maintain the cell wall structure,thereby slowing down the decline of fruit firmness,maintaining fruit quality,and prolonging the shelf life of strawberry fruit.（3）5 μmol·L^-1 SNP treatment up-regulated the expression level of Fa LAC,downregulated the expression levels of Fa POD and Fa GT,increased the laccase（LAC）activity,and decreased the tannase（TAN）,peroxidase（POD）and glucosyltransferase（GT）activities,promoted the accumulation of ellagic acid in strawberry fruit,enhanced the antioxidant capacity of strawberry fruit,and maintained good fruit quality.The above results indicated that 5 μmol·L^-1 SNP treatment was a effective treatment for maintaining strawberry fruit quality,which inhibited fruit softening,improved fruit antioxidant capacity,and maintained postharvest strawberry by regulating cell wall metabolism and ellagic acid metabolism.And it provided an experimental basis for the application of SNP in strawberry fruit storage and preservation.