Study On The Growth And Prevention And Control Of Root Rot Of Panax Notoginseng By Nitrogen Nutrition And Aromatic Essential Oil

Objective:Panax notoginseng/Sanqi has been suffering from root rot,which affected the yield and quality of Sanqi and restricted the sustainable development of the Sanqi industry greatly.In order to explore a scientific nitrogen fertilizer management model,the study was focused on the growth,active ingredients and resistance indicators of Sanqi with the treatment of different nitrogen forms and pathogen infection.At the same time,we explored the inhibitory activities of essential oils on pathogens of Sanqi root rot.The"prevention"of nitrogen nutrition and the"control"of essential oil on root rot were combined to provide a theoretical basis for the prevention and control of Sanqi root rot and open up new ideas for plant pathology research.Methods:（1）We treated the two-year-old P.notoginseng with different nitrogen forms,and infected it with Fusarium oxysporum for investigating differences of the growth（chlorophyll content,disease index and biomass）and active components（saponin,soluble sugars and flavonoid）of P.notoginseng.（2）Exploring the effects of different nitrogen forms and pathogen infection on four resistant enzyme activities（Superoxide Dismutase（SOD）,Peroxidase（POD）,Polyphenol Oxidase（PPO）and Phenylalanine Ammonia Lyase（PAL））,phenols,lignin and H₂O₂content of P.notoginseng.（3）We extracted essential oils from Chinese medicine,Artemisiae argyi folium and Acori tatarinowii rhizome,by steam distillation method,identified and analyzed composition of essential oils by GC-MS.Then we evaluated inhibition rates of essential oils on the mycelium of root rot pathogens（Fusarium oxysporum,Fusarium solani and Cylindrocarpon destructans）and Colletotrichum gloeosporioides by Oxford cup method Moreover,the minimum inhibitory concentration（MIC）of essential oils and their main components were measured by 96-well plate method.Finally,we assessed the combined antifungal effects of essential oils and hymexazol by two-dimensional checkerboard method.（4）We tested the antifungal activities of essential from Pogostemonis herba and Eupatorii herba based on above methods.Furthermore,the effect of essential oils on the annual P.notoginseng infected by F.oxysporum was evaluated.Results:（1）There were no significant differences in the growth and saponins content of P.notoginseng with different nitrogen forms treatment.The disease indexes were significantly lower with ammonium to nitrate in the ratio of 0:100 and 25:75,and it increased when the ratio of ammonium to nitrogen increased.The content of soluble sugar and flavonoid had upward trend with the ratio of NH₄⁺-N increasing and decreased after infected by F.oxysporum.（2）The activities of POD,PPO and PAL had upward trend with the increase of the ratio of NH₄⁺-N.There was a slight reduction of the activity of SOD after pathogen infection.Meanwhile,phenols and lignin accumulated as activities of POD,PPO and PAL increased with the ratio of ammonium to nitrogen increase.The PAL activity and the content of phenols and lignin increased sharply when the ratio of ammonium to nitrate was25:75.（3）The main composition of essential oil from Artemisiae argyi folium were（-）-caryophyllene oxide,（-）-β-caryophyllene,cineole,camphor and myrtenal.That of Acori tatarinowii rhizome wereβ-asarone andα-asarone.Essential oils and their main components exhibited antifungal activities,and the antifungal activities of main components were generally better.The antifungal activitiesβ-asarone andα-asarone were comparable to that of hymexazol.When essential oils were compatible with hymexazol,they had an additive effect on F.oxysorum and F.solani.（4）The main composition of essential oil from Pogostemonis herba were pogostone and patchouli alcohol,and that of Eupatorii herba were thymol and（-）-β-caryophyllene.Essential oils exhibited different inhibitory activities on pathogenic fungi and the antifungal activity of essential oil from Pogostemonis herba was better.The antifungal activities of pogostone,patchouli alcohol,thymol and（-）-β-caryophyllene were stronger,especially pogostone whose antifungal activity was better than hymexazol.The mixed antifungal effects of essential oil and hymexazol on pathogenic fungi were additive.When essential oil from Eupatorii herba and hymexazin were combined,there was a synergistic effect on C.destructans.Essential oil from Pogostemonis herba and Eupatorii herba had control effect on annual P.notoginseng infected with F.oxysporum in vivo.Conclusion:There were no significant differences in the growth and saponins content of P.notoginseng with different nitrogen forms treatment.The content of soluble sugar,flavonoid had upward trend with the ratio of NH₄⁺-N increasing.The content of soluble sugar and flavonoids and SOD activity decreased,and activities of POD,PPO and PAL increased after pathogen infection.Meanwhile phenols and lignin accumulated.The disease index was the lowest when the ratio of ammonium to nitrate was 25:75,which is beneficial for P.notoginseng to resist the root rot pathogen F.oxysporum.Essential oils from Artemisiae argyi folium,Acori tatarinowii,Pogostemonis herba and Eupatorii herba and their main components exhibited different antifungal activities against pathogens of P.notoginseng root rot.The antifungal activities of main components were better.Notably,pogostone exhibit excellent antifungal activities.In addition,essential oils from Pogostemonis herba and Eupatorii herba had prevention and control effect on P.notoginseng root rot in vivo.