| Aconitum carmichaelii Debx.was cultivated over 1300 years in Sichuan Province,China,and Jiangyou is the genuine producing area.ACONITI RADIX is the seminal root processing product of A.carmichaelii,which has the functions of reviving the sun,relieving the adversity,supplementing the fire and assisting the yang,etc.ACONITI LATERALIS RADIX PRAEPARAIA is the dry mother root,which has the effects of hurricane dehumidification,warming and relieving pain.Downy mildew Aconiti is one of the most harmful diseases in the cultivation.It has the characteristics of high incidence,strong seasonality and high infection rate.The pathogen is Peronospora aconiti Yu,which is an obligate parasite.In nature,the interaction between pathogens and host plants is a ubiquitous phenomenon.When subjected to disease stress,the plant will often produce a series of changes to form a variety of defense mechanisms in order to form a strict defense system against pathogenic bacteria.Host physiological changes caused by pathogen infection may also affect the composition of rhizosphere soil and its endophytic microbial communities and their related functions.In order to further the study of P.aconiti,this research systematically determined the biological characteristics of it,and laid the foundation for further research on the downy mildew Aconiti.To explore the effects of downy mildew on the physiological and biochemical,endophytic and rhizosphere actinomycetes of A.carmichaelii,this research studied on the changes of different physiological states and their rhizosphere and endophytic actinomycetes diversity and community structure before and after susceptibility.The main results are as follows:1.Initially clarified the germination conditions of the sporangia of downy mildew AconitiThe sporangia of P.aconiti germinated in the form of germ tube.The sporangia germinated in the range of 4-25 ?,and the germination rate was the highest at 18 ?.When relative humidity was lower than 95%,sporangia did not germinate,and sporangia germination rate was the highest under 100% relative humidity.The sporangia germinated in the range of pH 5.74-8.06,the sporangia germination rate was higher than other conditions in pH 5.93,but the overall germination rate was low.The sporangia of P.aconiti was inhibited by four carbon sources: glucose,sucrose,soluble starch and glycerol,which were all lower than the germination rate in distilled water.In the inoculation experiment,A.carmichaelii leaves showed brown necrotic lesions and allergic reactions.2.The variation characteristics of physiological and biochemical indexes of A.carmichaelii under downy mildew Aconiti stress were studied.With the increase of disease grade,the chlorophyll content in P.Aconiti leaves decreased continuously.The soluble sugar content showed a "M" trend of increasing.The SOD content was lowest in the 0-grade of healthy leaves,highest in 4th-grade with the most serious disease,the difference was extremely significant among other grades(P(27)0.01).The activities of POD,PPO and PAL all showed an "N" shape change trend.MDA content increased with the increase of disease grade.Before and after the infection with downy mildew Aconiti,there were significant differences in physiological and biochemical indexes related to disease resistance.3.The variation characteristics of endophytic and rhizospheric actinomycetes in A.carmichaelii infected by downy mildew Aconiti.279 strains of actinomycetes were isolated in this study.After repeating,57 strains were obtained.Among them,10 strains belonged to the same strain,21 strains were unique to the rhizosphere soil of healthy plants,and 26 strains were unique to the rhizosphere soil of diseased plants.Compared with healthy A.carmichaelii,the rhizosphere soil of which was infected with downy mildew Aconiti contained more culturable actinomycetes.A total of 20 endophytic actinomycetes were isolated from the mother roots,seminal root,stems and leaves of healthy and diseased A.carmichaelii.Endophytic actinomycetes isolated from diseased plants were all Streptomyces.Healthy plants contained more kinds of endophytic actinomycetes than diseased plants,and they did not contain mutual strains.The structure and diversity of actinomycetes in rhizosphere and endophyte of A.carmichaelii were changed by the infection of downy mildew Aconiti.15 strains of actinomycetes with strong antagonistic activity against the tested pathogenic bacteria were screened out from the above 71 strains actinomycetes from endophytic and rhizosphere soil. |
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