Preharvest Multiple Stroby And BTH Sprays Strength Cell Wall Of Development And Inhibite Fruit Softening Of Harvested Muskmelon

The muskmelons belong to climacteric fruit,which have an active postharvest metabolism,and the fruits are easily soften during postharvest.The cultivar ‘Agate’ of muskmelons was used as material.The plants were sprayed for 4 times with Stroby at 400 mg/L,Benzo(1,2,3)-thiadiazole-7-carbothioicacid S-methyl ester(BTH)at 100 mg/L and salicyl hydroximic acid(SHAM)at 1mM during fruit development respectively,at young fruit period(2 weeks after flowering),enlarging period(3 wk after flowering),netting period(4 wk after flowering)and mature period(preharvest 48h).The changes were analysed on cell wall metabolism key enzymes and components during fruit development.The changes were also determined on weight loss,firmness,cell wall components,cell wall-degrading enzymes activity and related gene expression of fruit at harvest and during cool storage.The effects of preharvest sprays were explored on strength of cell wall during feruit development and soften of fruit during harvest at molecular and biochemical levels.The results indicated as follows:1.Stroby and BTH treatments effectively increased the activity of sucrose synthase(SuSy)and expression of CmSuSy and CmCESA of fruit,enhanced the content of CDTA soluble pectins(CSP),sodium carbonate soluble pectins(DASP),cellulose,hemicelluloses,hydroxyproline rich glycoproteins(HRGPs)and lignins,promoted the synthetic of cell wall components in fruit during development.2.Stroby and BTH treatments decreased the weight loss,maintained firmness of fruit at harvest and during storage.The treatments also retarded conversion of propectin to water soluble pectins(WSP),maintained a higher content of CSP,DASP,cellulose,hemicellulose,HRGPs and lignins,and delayed fruit postharvest softening.3.Stroby and BTH treatments inhibited activity of pectin methylesterase(PME),polygalacturonase(PG),cellulase(Cx)and β-gluosidase(β-Glu),reduced the gene expression of CmPME,CmPG and CmCx,prevented the release of cell wall components and maintained higher fruit firmness at harvest and during storage.4.Stroby and BTH treatments increased of the activity and gene expression of Peroxidase(POD),and effectively enhanced bands activity of POD isoenzyme.The treatments also increased the content of H2O2,promoted accumulation of H2O2 in the cell wall of fruit.Furthermore,SHAM treatment inhibited the accumulation of H2O2 induced by Stroby and BTH,and reduced activity and expression of POD,weaked the cross-linking of cell wall of fruit.In conclusion,Stroby and BTH multiple sprays improved cell wall metabolism enzymes activity and related gene expression,promoted the synthetic of cell wall components in fruitduring development,and enhanced cell wall strength.Moreover,Stroby and BTH treatments inhibited activity and related gene expression of cell wall degrading enzymes,prevented the release of cell wall components,maintained fruit firmness,and delayed fruit softening at harvest and during storage.