| In recent years,the application of natural botanical fungicides from plants is considered to be a practical alternative to chemical synthetic fungicide,which has become a major focus.Cynanchum amplexicaule is one of traditional Chinese medicinal herbs.In this study it was used to separate and purify the active compound using of Penicillium digitatum and Penicillium italicum as the indicator,the antifungal mechanism of antifungal richment from C.amplexicaule was studied,then the induction mechanism of antifungal richment against citrus green mold was analyzed,at the same time,the effect of it on the storage of citrus was explored.The main research results are as follows:1.C.amplexicaule was extracted with aqueous ethanol refluxing using 50% ethanol as extractant,separation and purification of its extract were carried out by extraction,AB-8macroporous resin,silica gel column chromatography and thin layer chromatography(TLC).The activity of components were detected with oxford cup,and the component which showed the most powerful activity was selected for the next step.Finally,five components were obtained,the diameter of inhibition zone of component 1 against P.digitatum was 29.48 mm,showed that it has strong inhibitory effect on P.digitatum.Therefore,component 1 is the antifungal richment of C.amplexicaule.2.With the antibacterial circle diameter of powder the antibacterial properties were characterized examined.In this paper,it were studied that the effects of the antifungal richment of C.amplexicaule at different concentrations on antifungal activity against P.digitatum,and the minimum inhibitory concentration(MIC)and minimum bactericidal concentration(MBC)of Penicillium digitatum was determined based on these.The antifungal richment was utilized to study the antifungal activities and mechanism against P.digitatum.The spore germination,extramembrane conductivity,mycelium morphology,cell water retention and content of lipid and ergosterol were discussed to explain the potential mechanism,the stability of the antifungal enrichment was also investigated.The results showed that the antifungal richment showed higher antibacterial activity with the increasing of concentrations,the change of temperature or p H has no obvious effect on antibacterial activity.The MIC and MBC were 0.3mg/m L 、0.6mg/m L,which could prominently inhibit the spore germination of P.digitatum.In addition,electrolyte exosmosis rate increased,water retaining rate decreased obviously in the treated mycelium.The antifungal richment also could cause the decrease of lipid and ergosterol contents led to disruption of membrane integrity,an increase in the relative leakage,and thereby strongly inhibits growth and propagation of P.digitatum.3.Newhall navel orange inoculated 3mg/m L(5MBC)of the antifungal richment of C.amplexicaule,then inoculated P.digitatum.The incidence and lesion diameter were determined,and fruit quality and changes of defense-related enzymes were analyzed as well.The results showed that the lesion diameter and incidence of green mold wa s evidently lower than that of the control.Orange treated with the antifungal richment kept the content of the soluble solids,titratable acid and Vitamin C at a high level,and reduced MDA content to decrease the level of cell membrane lipid peroxidation.The activities of POD、PPO、PAL in treatment effectively improved before 72 h of incubation,and peaked at 72 h,which earlier than that in the control group(96h),and the maximum POD、PPO、PAL were 1.54、1.99、1.92 times higher than the control group respectively.The results indicated that the antifungal richment induced the increase of defense enzyme activity in advance to enhance disease resistance of the orange,thus controlling green mold.4.A compound coating agent was made by sodium alginate,other chemicals and added 0.3mg / m L(MIC)of the antifungal richment.Coating agent with and without the antifungal richment were applied to Nanfeng mandarins,changes in quality parameters and enzyme activities in mandarin with 2 kinds of coating were measured during storage at(5±1)°C.The compound coating treatment significantly reduce the number of fruit rots,the weight loss rate and MDA content,and it also could decrease the loss of total soluble solids,total phenols,total sugar and Vitamin C by inhibiting function of respiration during cold storage.The activities of POD、PPO、PAL were improved effectively at earlier storage,while the activities of POD、PAL and LOX were inhibited at later storage periods to delay senescence of Nanfeng mandarin.In anaphase storage,the effect of PPO activity was not obvious.The results indicated that coating enriched with 0.3mg/m L(MIC)of the antifungal richment had a better effect on storage and preservation of Nanfeng mandarins. |
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