The Inhibitory Effect And Mechanism Of Intense Pulsed Light On The Black Spot Disease During Transportation And Storage Of Apricot Fruit

‘Xiaobai’apricot（Prunus armeniaca L.）has a long history of cultivation and is a popular fruit among consumers.However,the harvested fruits tend to soften and age easily,making them susceptible to mechanical damage and pathogen infection,resulting in economic losses and hindering the development of the industry.Therefore,it is particularly important to study effective postharvest storage and transportation methods to preserve the freshness of apricots.This study focuses on‘Xiaobai’apricot and explores the effects of Intense Pulsed Light（IPL）treatment on apricot fruits during simulated transportation.The physiological mechanisms of IPL treatment on storage control and simulated transportation damage are analyzed from the perspectives of storage quality,antioxidant system,and cell wall metabolism.Furthermore,the physiological and biochemical changes,enzymatic activities,gene expression,and transcriptomics of IPL-treated apricot fruits under A.alternata infection are investigated to reveal the regulatory mechanisms of IPL treatment on postharvest apricots.The aim is to provide theoretical references for the application of IPL in apricot preservation.The main research results are as follows:1.The effects of IPL treatment on post-harvest apricot quality and antioxidant system were investigated after simulated transportation vibration.IPL treatment showed good potential in preventing or improving quality loss caused by vibration and extending shelf life.IPL treatment before simulated transportation effectively inhibited the growth of apricot skin microbiota.In addition,IPL treatments increased the accumulation of antioxidants,enhanced the activity of antioxidant enzymes,inhibited the migration and loss of water,delayed the destruction of apricot cell structure,and prevented the decline of apricot quality.It is worth noting that IPL treatment in this study improved the storage ability of apricot fruit.2.The effects of IPL treatment on postharvest apricot cell wall metabolism were investigated.IPL significantly delayed the decrease in fruit firmness,inhibited the increase in cell membrane permeability,and accumulation of MDA.During storage,IPL treatment significantly increased the content of CDTA-soluble pectin,Na₂CO₃-soluble pectin,cellulose,and hemicellulose in pectin,and decreased the content of soluble pectin.IPL treatment significantly reduced the activities of cell wall degradation enzymes PG,CEL,PME,andβ-GAL.In addition,electron microscopy observations showed that IPL pretreatment delayed the degradation of apricot cell walls.Therefore,IPL treatment can reduce the quality loss caused by vibration damage during storage and transportation by delaying the metabolism of apricot cell walls.3.The study analyzed the regulatory effect of IPL treatment on black spot disease in post-harvest apricots.After IPL treatment,the disease index of apricots was significantly reduced,indicating that IPL can enhance the defense response of apricots against A.alternata.IPL induced the activity of disease resistance enzymes（CHI,β-1,3-G,SOD,CAT,PAL,4CL,and C4H）in apricots,increased the content of phenolic and flavonoid substances,and reduced the sensitivity of apricots to A.alternata.The results suggest that IPL can inhibit the occurrence of post-harvest black spot disease by inducing the disease resistance of apricots.4.This study used transcriptomics to investigate the effect of IPL on the transcriptome of apricot in response to A.alternata infection.GO and KEGG enrichment analyses were used to analyze the DEGs in apricot.The results showed that up-regulated modules of DEGs were mainly related to apricot defense,while down-regulated modules were mainly related to apricot growth and development.It was found that A.alternata triggered a corresponding signal transduction in apricot,and IPL treatment promoted this effect,leading to significant up-regulation of genes encoding some secondary metabolites in apricot（such as flavonoids）,which were most closely related to the plant hormone signal transduction pathway.This pathway was related to plant-pathogen interactions,MAPK signal pathways in plants,and phenylpropane biosynthesis pathways.Combined with the control effect on black spot disease,it was concluded that apricots synthesize secondary metabolites in response to infection.