Application Of Strigolactone In Controlling Softening Of Postharvest Strawberry Fruit

Strawberry is rich in nutrition,and has a market value,deeply loved by people.The skin of strawberries is thin,and it is easy to be damaged during the process of harvest,transportation and storage,leads to its decay and deterioration after harvest.Therefore,it is important to develop a simple and effective method for maintaining strawberry fruit quality.Strigolactone（SL）plays an important role in regulating plant growth and development.As a natural plant hormone,it plays an active role in the preservation of fruit trees and has become a research hotspot.However,there are few reports on the effects of SL on the softening of postharvest fruit.In this paper,we used“Tianbao”strawberry as the experimental material.strawberries were soaked with six different solutions,Include 0,0.5,1,1.5,and 2μmol L^-1 SL and 5μmol L^-1 6-phenoxy-1-phenyl-2-（1H-1,2,4-triazol-1-yl）hexan-1-one（Tis-108）and the fundamental quality indexes of strawberry fruit such as respiration rate,weight loss rate,hardness,color difference,relative conductivity and soluble solid content（SSC）were measured.It was preliminarily determined that 1μmol L^-1 SL had the best preservation effect on strawberry fruit.The softening of fruit is related to lignin,pectin,cellulose and hemicellulose metabolism in cell wall metabolism Therefore,on this basis,this experiment explored the regulation of SL treatment on the metabolism of lignin,pectin,cellulose and hemicellulose of postharvest strawberry fruit,so as to explore the influence of SL on fruit softening.The main results are as follows:（1）It was found that different concentrations of SL maintained fruit quality to a certain extent.Among them,1μmol L^-1 SL treatment can better inhibit the increase of strawberry fruit respiration rate and relative conductivity,delayed the degradation of fruit nutrients and water loss,inhibited the increase of fruit weight loss,and better maintained the fruit hardness.In addition,the increase of color difference value of postharvest strawberry fruit was also inhibited,which delayed the process of fruit browning.Treatment with 1μmol L^-1 SL effectively increased the content of soluble solids and maintained the quality of postharvest fruits.（2）SL treatment increased the relative expressions of Fa PAL and Fa4CL and inhibited the relative expressions of Fa POD in lignin metabolism pathway,increased the activities of phenylalanine ammonia lyase（PAL）and 4-coumaric acid Co A ligase（4CL）,inhibited the activities of peroxidase（POD）and increased the lignin content,enhanced the toughness of the cell wall.In the pectin metabolic pathway,SL treatment down-regulated the relative expressions of Fa PG,Faβ-Gal and Fa PME,and thus inhibited polygalacturonase（PG）,β-galactosidase（β-Gal）,pectin methylesterase（PME）activity,SL slows down the decline of CDTA-pectin（CSP）and Na₂CO₃-pectin（NSP）soluble,as well as the rise of water-soluble pectin（WSP）,maintained the intercell wall stickiness of strawberry fruit during storage.（3）SL treatment down-regulated the relative expression levels of Fa XET and Fa Glu in the metabolic pathways of cellulose and hemicellulose,and inhibited xyloglucan endotransglucosylase（XET）and glucosidase（Glu）,cellulase（Cx）activity,delayed the degradation of cellulose and hemicellulose and maintained the integrity of the cellulose-hemicellulose network.Thus,it can delay the decline of fruit hardness,delay the process of fruit softening,and maintain the quality of fruit.These results showed that SL treatment could delay the quality degradation of strawberry during storage,and 1μmol L^-1 SL had the best effect.Subsequent studies have found that SL may delay the decline of hardness of strawberry and maintain good fruit quality by regulating the contents of substances related to the metabolism of lignin,pectin,cellulose and hemicellulose,enzyme activity and gene expression.These results provide theoretical basis and technical support for the application of SL in postharvest fruit storage and preservation.