Effect Of Postharvest Sodium Nitroprusside Treatment On The Quality,Shikimate And Phenylpropanoid Pathway Of Apple Fruit

Senescence and decay are the important reasons that leading to quality deterioration and erosion of apples after harvest.Sodium nitroprusside(SNP)is a donor of exogenous nitric oxide(NO)which can be released by reduction and decomposition.Therefore,SNP is an important carrier for studying the characteristics and functions of NO.Apple fruit(cv.Fuji)were treated with 1.0 mmol /L SNP to study its effects on quality,sucrose metabolism,shikimate and phenylpropanoid pathway of apple fruit during storage at room temperature.The main results were as following:1.Postharvest SNP treatment significantly delayed the peaking time of respiratory intensity,reduced the respiratory intensity of apple fruit,maintained a high level of flesh firmness,the content of titratable acid(TA)and ascorbic acid(AsA)of apple fruit,reduced the consumption of soluble solids content(SSC)and delayed the increase of malondialdehyde(MDA)and soluble sugar content of apple fruit.However,SNP did not significantly affect weight loss of apple fruit during storage.2.Postharvest SNP treatment significantly suppressed the activity of sucrose synthase-cleavage(SS-c)and invertase enzyme,enhanced the activity of sucrose phosphate synthase(SPS)and sucrose synthase-synthesis(SS-s),and increased the net activity of sucrose metabolic enzyme of apple fruit.The expression of MdSPS,MdSS,MdNI,hexokinase(MdHK)and fructokinase(MdFK)genes of apple fruit were also up-regulated by SNP treatment.3.Postharvest SNP treatment significantly inhibited lesion development of apple fruit inoculated with Penicillium expansum,enhanced the expression of 3-dehydroquinate dehydratase(MdDHQS),shikimate dehydrogenase(MdSKDH),shikimate kinase(MdSK)and 5-enolpyruvylshikimate 3-phosphate synthase(MdEPSPS)genes in shikimate pathway,increased shikimic acid and tryptophan contents during early period of storage,and enhanced the content of tyrosine and phenylalanine of apple fruit during the entire storage period.4.Postharvest SNP treatment significantly enhanced the expression of phenylalanine ammonia lyase(MdPAL),cinnamate-4-hydroxylase(MdC4H),4-coumarate: coenzyme A ligase(Md4CL)and chalcone isomerase(MdCHI)genes,and enhanced the content of lignin,total phenolic compounds and flavonoids in phenylpropanoid pathway of apple fruit during the entire storage periodThese results suggest that postharvest SNP treatment could modulate the activity of enzymes and genes in expression sucrose metabolism to delay quality breakdown of apple fruit during room temperature storage,and regulate the shikimate and phenylpropanoid pathways to enhance disease resistance against blue mould of apple fruit.