Study On The Mechanism Of Disease Resistance Based On The Regulation Of Redox Status And WRKY Transcription Factors In Postharvest Strawberries

Strawberry fruit is well received by consumers because of the quality characteristics such as bright color,soft and juicy,delicacy and rich nutrition and so on.However,comparing with a majority of fruits,it is easily infected by pathogenic fungi on account of the high water content and vigorous post-harvest physiology,which is adverse to storage and freshness.At present,low temperature and chemical fungicide are the main measure to extend the shelf life of fruits and vegetables in the domestic and overseas.Nevertheless,with the strengthening of human awareness of environmental consciousness and the rise of drug resistance of pathogenic bacteria,the use of chemical fungicides has been challenged,so the new typical green preservation technology is necessary.The study was designed to investigate the effect of BABA and BTH treatment on the inhibition of decay in strawberries,and according to the changes of reactive oxygen metabolism and reduction potential in strawberry?Fragaria×ananassa?fruits,discussing the regulation mechanisms of induce resistance induced by BABA and BTH treatment.Moreover,it is also studied the disease-resistance mechanism induced by WRKY transcription factors in BABA-treated strawberry fruits through transcriptomics,hoping to provide the basis for the application of BABA and BTH in the disease resistance of post-harvest strawberry fruits.The results were as follows:?1?The effects of BABA and BTH treatment on the decay rate and reactive oxygen metabolism in postharvest strawberry fruit were studied.The result showed that 10 mmol/L BABA and 0.1 mmol/L BTH treatment alleviated the degradation of AsA?TA and TSS,maintained a high level of total phenol content?DPPH free radical scavenging rate and total reducing power.Moreover,the two treatment inhibited the accumulation of MDA and the increase of LOX activity,preventing the membrane lipid peroxidation of strawberry fruits.In addition,BABA and BTH treatment also restrained the accumulation of reactive oxygen species such as H₂O₂ during storage by regulating the activities of oxidation-related enzymes such as SOD?CAT and APX and the content of antioxidants such as GSH.This indicated that BABA and BTH treatment could reduce the decay rate by improving the antioxidant capacity of strawberry fruits.?2?The effects of BABA treatment on storage quality and internal reduction potential of postharvest strawberry were investigated.It is implied that BABA at 10mmol/L effectively reduced the disease incidence,promoted the accumulation of SA and NO,increased the activities of G6PDH and 6PGDH as well as the content of NADPH,which were the key enzymes in the pentose phosphate pathway and GSH-AsA cycle.Besides,it also stimulated the expression of PR genes and the high content of NADPH offered more reduction power.However,6-AN treatment inhibited the accumulation of SA and NO as well as the key enzyme activities in the pentose phosphate pathway,resulting in the reduction of redox status,the increase of disease incidence and the decrease of PR genes expressing.These results turned out that BABA treatment could induce the increase of reduction potential in strawberry fruit cells,which was conducive to disease resistance.?3?The effects of BTH treatment on redox status and disease resistance in postharvest strawberry fruits.It is confirmed that BTH at 0.1 mmol/L effectively debased the disease rate and lesion diameter.From the expression levels of PR genes such as FaPR1?FaPR5?FaCHI-1 and Fa?glu,it is determined that the gene expression retained a higher level in treated with 0.1 mmol/L BTH and then inoculated strawberry fruits.Whereas in 0.1 mmol/L BTH alone treated fruits,the PR genes showed a lower expression level at the early stage of storage,which is no significant difference comparing with the control fruits,and then gradually rising to the same level with BTH and inoculated fruits during the later stage of storage.Instead,the PR genes expression in the alone inoculated fruits presented a rapid increase at the early stage,and then decreased slowly.This suggested that the0.1mmol/L BTH treatment had induced disease resistance through the mechanism of Priming,and only activated the defense reaction when the strawberry fruit was infected with pathogens,which could trigger the stronger defense response.?4?The responses to postharvest disease resistance induced by BABA,pathogeninoculation and BABA+inoculation in strawberry fruits were studied at transcription level.BABA treatment could effectively stimulate the key genes expression of AsA-GSH cycle and reactive oxygen metabolism system.It was found that BABA treatment and pathogen inoculation could induce the expression of PR genes by regulating different WRKY transcription factors.The results indicated that there were some differences between the priming reaction induced by 10mmol/L BABA and the disease resistance mechanism induced by direct pathogen inoculation,which provided the molecular biological basis for the application of BABA in postharvest strawberry fruit.