Partial Mechanism Of Applying Acibenzolar-S-methyl After Harvest Inducing Disease Resistance Against Black Spot In Docteur Jules Guyot Pears

Senescence and decay are the important reasons that leading to quality deterioration of pears after harvest.Doteur Jules Guyot pears were used as the materials to investigate the effect of 100 mg L^-1 acibenzolar-S-methyl?ASM?treatment on lesion development of fruit inoculated with Alternaria alternata?A.alternata?,reactive oxygen species?ROS?and fatty acid metabolism,phenylpropanoid pathways and quality parameters during room temperature storage.The main results are as following:1.ASM treatment significantly inhibited lesion development of pear fruit inoculated with A.alternata.ASM treatment remarkably suppressed hydrogen peroxide?H₂O₂?content,enhanced catalase?CAT?,superoxide dismutase?SOD?,ascorbate peroxidase?APX?,dehydroascorbate reductase?DHAR?,glutathione reductase?GR?,and monodehydroascorbate reductase?MDHAR?activities and reduced glutathione?GSH?content in pears.Moreover,postharvest ASM dipping remarkably enhanced PcSOD,PcCAT,PcAPX and PcDHAR expressions in pears.2.Applying ASM after harvest distinctly enhanced fatty acid synthetase?FAS?activity,decreased lipoxygenase?LOX?,hydroperoxide lyase?HPL?,alcohol dehydrogenase?ADH?,and alcohol acyltransferase?AAT?activities and malondialdehyde?MDA?content in pears.Meanwhile,ASM treatment distinctly inhibited PcPLD,PcLOX,PcHPL,PcAAT and PcAAT expressions in pears.3.The activities of phenylalanine ammonialyase?PAL?,4-coumarate/coenzyme A ligase?4CL?,cinnamate 4-hydroxylase?C4H?,cinnamyl alcohol dehydrogenase?CAD?,peroxidase?POD?and polyphenol oxidase?PPO?were also significantly enhanced by ASM in pears.The results also demonstrated that application of ASM postharvest accelerated the accumulation of lignin,total phenolic compounds,flavonoids and anthocyanin in pears.Expressions of the selected genes PcPAL,PcPOD,PcPPO,PcCAD and PcC4H were remarkably increased by postharvest ASM treatment.4.ASM treatment significantly inhibited respiratory rate and ethylene release,reduced weight loss,suppressed the decline of flesh firmness and ascorbic acid content,accumulation of soluble pectin,increase of a value and b value,and maintained higher propectin content and titratable acid in pears.These findings suggest that postharvest ASM treatment could significantly enhance the activities of SOD,CAT,APX,GR,MDHAR,and DHAR,GSH and H₂O₂ contents,the expressions of PcSOD,PcCAT,PcAPX,PcDHAR in ROS metabolism;inhibit the activities of LOX,HPL,AAT,and ADH,MDA content,the expressions of PcLOX,PcHPL,PcAAT,PcADH,PcPLD and enhance the activity of FAS in fatty acid metabolism;enhance the activities of PAL,4CL,C4H,PPO,POD,and CAD,the accumulation of metabolic products and the expressions of PcPAL,PcC4H,PcPPO,and PcCAD,to increase resistance against black spot.Moreover,ASM tretament could inhibit respiratory rate,ethylene release,and the degradation of pectin to delay senescence of pears.