| Phenols,a series of substances of plant secondary metabolites,are considered to be the most common resistance related substances in plants for its antibacterial,antioxidant and free radical scavenging ability.Phlorizin and ferulic acid,as component of phenolic substances,play a important role in plant disease resistance for their physiological and biochemical properties.In this study,we therefore investigated the direct inhibitory function of phlorizin and ferulic acid by cultivated B.cinerea in vitro,and the concentrations of vivo experiment were obtained by pre-test.‘Pink Lady'apple fruits were soaked in phlorizin or ferulic acid solution for 20 min,incubated for 12 h,and inoculated with 20?L of a B.cinerea conidial suspension.Distilled water was used instead of phlorizin or ferulic acid as a control.Samples were collected regularly for the measurement of disease-related-enzyme and disease-related-substance,with the incidence and diameters of lesions surrounding each wound site measured and recorded at the same time.The results showed that:1.The growth of B.cinerea can be directly inhibited by phloridzin in vitro,and with the phloridzin concentration increasing in culture medium,this kind of inhibition was also reinforced.When the phloridzin concentration reached 1.0 g/L,there is no colony formatted of B.cinerea in the culture.Thus concluded that 1.0 g/L is the smallest concentration of ferulic acid for inhibiting B.cinerea completely.2.Phlorizin treatment significantly decreased the incidence of gray mold rot in pink lady apple fruits,and effectively suppressed the expansion of lesions in vivo.Concurrently,it also changed the activity of phenylpropanoid pathway and lignin biosynthesis pathway correlate enzyme.Phenylalanine amonialyase?PAL?,trans-cinnamic acid-4-hydroxylase?C4H?and polyphenol oxidase?PPO?were higher than the control in the whole period,which effectively promoted the accumulation of total phenol and flavonoids,and had a direct inhibitory effect on the pathogen.The activity of 4-coumarate-CoA ligase?4-CL?,cinnamoyl-CoA reductase?CCR?,cinnamyl-alcohol dehydrogenase?CAD?in lignin metabolism pathway significantly increased compared with the control in the early stage,then decreased,and shown an upward trend in the end.The activity of laccase and peroxidase?POD?in the treatment group was higher than that of control,which promoted the final step of lignin biosynthesis,increased the accumulation of lignin,and hindered the further prevented of B.cinerea.Phlorizin treatment also effectively increased the contents of GSH and ASA,and reduced the content of hydrogen peroxide?H2O2?and the production rate of superoxide anion(O2·-)coincidentally,therefor the degree of membrane lipid peroxidation and cell death rate senescence of fruit were decreased,the resistance of fruits increased.3.Ferulic acid has bioactivity for the inhibition of B.cinerea growth.With the ferulic acid concentration increasing in culture medium,the inhibitory effect was more and more strong,when the concentration of ferulic acid was up to 0.80 g/L,the growth of B.cinerea was completely inhibited,and this kind of inhibiting function was directly instead of changing the growth environment of B.cinerea.4.Compared with the control,ferulic acid treatment was found to significantly increase activities of enzymes in the phenylpropanoid pathway and thus effectively improve total phenol and flavonoid accumulations.This treatment also affected the activities of enzymes in the lignin biosynthesis pathway,thereby promoting lignin production while decreasing disease incidence and lesion diameters.And the contents of GSH and ASA were increased.The production of hydrogen peroxide,superoxide radicals and malonaldehyde also decreased.On the basis of these findings,we conclude that ferulic acid treatment can augment the defense response of apple fruit by enhancing the activities of resistance-related enzymes and boosting the accumulation of resistance-related substances,thereby reducing the incidence of gray mold. |
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