Antifungal Effects Of Ramulus Cinnamomi Extracts On The Main Pathogens Of Citrus Postharvest Disease

Seventy-eight kinds of medicinal plant extracts were selected to screen potentialantifungal activity against Penicillium italicum and Penicillium digitatum, which are themain pathogens of postharvest citrus disease. Chemical fungicide sucha as prochloraz andbellkute often used in citrus postharvest, were regared as treatmeats in the research, whichwere compared with Chinese herbs extracts of the in-vitro antifungal effects. On the basis,Ramulus cinnamomi was screened to be the most effective inhibition material on the twoindicator fungus from the seventy-eight ethanol-extracts, and further study were processedon its antifungal mechanism, antifungal spectrum,extraction technology. In addition,Ramulus cinnamomi was mixed with commomly-used food additives in acidic condition,so as to achieve equal or better antifungal effects with less food additives, which were ofsignificance for the development of nuisanceless citrus fungicide and green control ofcrops disease.And the main results were as follows.1Oxford-cup tests and double broth dilution method were used to determine theantifungal activity of Chinese herbs ethanol-extracts, the result showed that Ramuluscinnamomi had remarkable inhibition effects on both Penicillium italicum and Penicilliumdigitatum, and the inhibition zones were34.57±0.78mm，31.56±0.66mm, respectively,while the minimum inhibitory concentrations (MIC) were3.13mg/mL，6.25mg/mL,respectively, the minimum fungicidal concentrations (MFC) were6.25mg/mL，12.5mg/mL, respectively. Moreover, its antifungal activities were better than1000times diluentbellkute, which the inhibition zones were17.03±0.21mm、16.07±0.21mm, respectively.And they were significantly different at the1%level by Ducan significance test.2Using ultrasonic assisted extraction technology, combined with single factorexperiment, and inhibition zones as indicators,antifungal effects of extract solventconcentration, solid-liquid ratio, extraction time and extraction temperature on Penicilliumitalicum and Penicillium digitatum were determined, the result showed that the bestextraction technology for Ramulus cinnamomi is95percent concentration of ethanol with2hours extraction time,1:10solid-liquid ratio and40℃extraction temperature. In addition,growth rate method was used to determine the antifungal activity of Ramulus cinnamomiethanol-extracts on the other fifteen kinds of phytopathogens such as Botrytis cinerea, theresult suggested that the extracts had lots of active ingredients and showed remarkableantifungal activity on the provided pathogens, so it had a broader antifungal spectrum.3Antifungal mechanism of Ramulus cinnamomi ethanol-extracts were conductedfrom four aspects, which were spore germination, cell membrane permeability, myceliummorphology, mycelium contents (soluble protein and total sugar content), the resultedshowed Ramulus cinnamomi ethanol-extracts could effectively inhibit spore germination ofthe two tested pathogens, increase its cell membrane permeability, thus leading to the leakage of mycelium contents, which had a serious impact on the growth and developmentof mycelium, then the mycelium showed different kinds of abnormal morphology, such asswelling, shrinking, breakage and so on, which could effectively achieve the fungicideeffect.4Damaging to the inoculation on Xinyu mandarin was used to study on the in vivobiological control effects of Ramulus cinnamomi ethanol-extracts, the results showed thatRamulus cinnamomi extracts can effectively inhibit the pathogens in vivo in adose-dependent manner, and had a significantly different among the treatment groups, theinhibition rates were41.18percents when the concentrations of the extracts were100mg/mL with the dealt of inoculating with the mixed spore suspension before the extracts,while inoculating the extracts before the mixed spore suspensions, the control efficiencywas better, which reached44.31percents at the same concentrations, so it made a bigdifference from the processing sequence of inoculating the plant fugicides and thepathogens on the control effects of green and blue mould in citrus.5Under certain acidic circumstance of pH3.3, the compound which contained1g/mL Ramulus cinnamomi ethanol-extracts,1%Potassium sorbate,1%Sodium benzoate,were completed according to the volume of1:1:1, and its inhibition zones on Penicilliumitalicum and Penicillium digitatum were44.40±0.44mm,41.83±0.15mm, respectively,while the inhibition zones of the Ramulus cinnamomi ethanol-extract at1g/mLconcentration were40.87±0.30mm and39.83±0.25mm,1%Sodium benzoate were43.80±0.26mm and39.17±0.45mm,1%Potassium sorbate were39.13±0.50mm and35.13±0.30mm,0.5%Potassium sorbate+0.5%Sodium benzoate were44.27±0.42mmand40.53±0.12mm,0.5%Sodium benzoate+0.5g/mL Ramulus cinnamomiethanol-extracts were44.23±0.15mm and40.67±0.23mm,0.5%Potassium sorbate+0.5g/mL Ramulus cinnamomi ethanol-extracts were43.37±0.21mm and40.40±0.20mm,Therefore, the antifungal effects of0.33%Potassium sorbate+0.33%Sodium benzoate+0.33g/mL Ramulus cinnamomi ethanol-extracts on the two pathogens were better than thesingle component and the other two compounds of them, moreover, the contents of thecompound constitutions were lower, and achieve synergy effect with less food additives.