Impact Of Postharvest Anthracnose,Enhancement Of Disease Resistance And Quality In Ripening Dragon Fruit By Exogenous Nitric Oxide Treatment

Anthracnose is one of the most important postharvest disease of dragon fruit(Hylocereus undatus),which has seriously effect on the quality of dragon fruit.In order to effectively control postharvest diseases of the dragon fruit,the white-fleshed dragon fruit were regarded as experimental material in the present study.Fruits were treated with the NO donor,sodium nitroprusside(SNP)by the immersion method,and some of fruits inoculated with Colletothrichum gloeosporioides.The impact of nitric oxide treatment on control of anthracnose caused by C.gloeosporioides in dragon fruit,its possible mechanisms and postharvest quality were investigated.The results are as follows:1.In vitro,SNP at concentrations of 0.05-4 mM did not significantly inhibited the mycelial growth of C gloeosporioides,C.truncatum and Fusarium dimerum.But in vivo,0.1 mM SNP treatment effectively suppressed the expansion of lesion in dragon fruit inoculated with C.gloeosporioides,and reduced the postharvest natural incidence and index of dragon fruit during storage period.These results showed that the reduction of postharvest diseases in dragon fruit was induced by enhancement of fruit resistance not inhibited the pathogen mycelial growth.2.NO treatment(0,1 mM SNP)enhanced the activities of defense-related enzymes including phenylalanine ammonia lyase(PAL),peroxidase(POD),polyphenol oxidase(PPO),cinnamate-hydroxylase(C4H),4-coumarate:Co A ligase(4CL)and also promoted the accumulation of the total phenolics,lignin and flavonoids content,enhancing the disease resistance for dragon fruit.3.NO treatment(0.1 mM SNP)also increased superoxide dismutase(SOD)and catalase(CAT)activities,and enhanced antioxidant capacity for dragon fruit.4.NO treatment(0.1 mM SNP)enhanced the activities of β-1,3-glucanase(GLU)and chitinase(CHI),which induced the accumulation of pathogenesis related proteins and enhanced the disease resistance for dragon fruit.5.NO treatment(0.1 mM SNP)effectively inhibited the respiration rate of dragon fruit during storage period,NO treatment effectively delayed the changes in soluble solids content(SSC),titratable acid(TA)and soluble protein content,maintained better fruit firmness,as well as reduced weight loss,which delayed the senescence of fruit and quality deterioration,and prolonged the storage period.