Study On The Relationship Between Storage Physiology,Membrane Lipid Changes And Core Browning Of Modest Harvest Yali Cooled In Different Method

Yali is the second major pear cultivar in china.Core-browning,induced by descent or chilling injury,causes the greatest losses during postharvest storage and transportation of yali fruits.To solve this problem,harvest at modest maturity and slow cooling are usually applied.However,this method can't inhibit occurrence of core-browning completely,and the mechanism of this method is still unclear.Probable mechanism such as carbon dioxide injury,chilling injury and senescent have been studied in recent years,however,studies in gene level are still insufficient.In this research,effect of modest maturity and slow cooling on core-browning occurrence,and influence on physiological indicators,enzymatic activity,and gene expression associated with chilling injury(saturated and unsaturated fatty acid content,Lipoxygenase activity,LOX/FAD expression)and related storage indexes(ethylene production,respiratory intensity,internal ethylene and CO2 concentration,flesh hardness,ACC oxidase activity,ACO expression)in core tissues had been studied.Conclusions are as follows:1.Slow cooling had delayed occurrence of yali core browning during cold storage,and the core-browning index of slow cooling treatment were significantly lower than rapid cooling treatment.2.Slow cooling had delayed the peak of fruit respiratory intensity and ethylene production.ACO expression in core tissues,fruits' internal ethylene and internal CO2 concentration of yali fruits were significantly inhibited by the treatment of slow cooling.Apart this,flesh hardness of yali fruits after slow cooling were obviously higher than fruits cooled rapidly during cold storage and shelf life,this treatment had ensured better quality of yali.3.Yali core tissues contain several types of fatty acid,such as oleic acid,linoleic acid,linolenic acid,stearic acid and palmitic acid et al.At the beginning of storage,the USFAs content of solw-cooled fruits were significantly higher than rapid-cooled fruits.During storage(60-180d),content of linolenic acid in rapid-cooled fruit was markedly higher than that in slow-cooled fruits.The DBI(Double-binding index)of both treatment fruits increased firstly and decreased with the extend of storage,and DBI of rapid cooled yali fruits were significantly higher than those cooled slowly.The yali FAD3,related with fatty acid metabolism,was cold-induced: FAD3 expression of rapid and slow cooling yali fruits were markedly up-regulated during cold storage.Beside this,FAD1 was induced by rapid cooling,and the relative expression of rapid-cooled fruits of FAD1 was markedly higher than that in slow-cooled fruits.Overall,slow cooling had kept a stable USFA content of fruits,beside this,inhibition of this treatment to LOX was helpful to sustain the normal function of membrane,and then avoided the core-browning.In conclusion,slow cooling had delayed the maturation of yali through the inhibitoion to ethylene biosynthesis by suppressing the ACO expression,and the other physiological indexes were stable during storage.Apart this,this treatment had also inhibited core-browning,by keeping stable DBI of membrane lipid and FAD expression,suppressing LOX expression and LOX activity during storage.