The Effect Of Pesticides On The Diversity Of Actinobacterial Community In The Cultivation Soil Of Panax Notoginseng

Sanqi(Panax notoginseng),a valuable medicinal plant in China,belonging to Panax genus,naturally lives in shade habit.In traditional Chinese medicine,it presents the functions of relaxing muscles,stimulating the blood circulation,allevating swell and pains.Due to cultivating under the shaded,warm and humid conditions with no tillage for more than two years,notoginseng plant is vulnerable to many sever diseases,especially the root disease.High doses of pesticides(fungicides)applicated in the cultivating notoginseng exacerbate the microbial imbalance.In this thesis,the unculture method – MiSeq and culture methods were employed to investigate the differences of actinobacterial communities between and within the groups treated with different fungicides.The aims were: i)to investigate the effects of fungicides on the soil actinobacterial communities;ii)to obtain the active isolates which are helpful to rich our actinobacterial library.In the detected actinobacterial sequences by MiSeq,the reads except the unclassified ones were assigned to 13 orders,25 families,34 genera.The culture-independent experimental results indicated that the actinomyces diversity index(Shannon index)were reduced in the soils treated by fungicides thiophanate-methyl/thiram,polyoxin,and mancozeb,while the index of the control(without fungicides)was increased.The microbial species richness indexes – ACE and Chao1 – presented lower trends in the fungicide-treated soils except for the mancozeb treatment.These results showed that the application of fungicides could decrease the actinobacterial diversity in the cultivation soil of Panax notoginseng.At the same time,the fungicides could affect the community and composition of bacteria in the notoginseng cultivation soil.The relative abundances of Acidothermus and Crossiella increased while those of Gaiella and Streptomyces decreased in the all soils treated with the fungicides.The number of Lysinimonas and Dactylosporangium was increased by mancozeb and decreased by thiophanatemethyl/thiram.The functional COG genes were investigated in all the soils treated with the fungicides.All detected COG gene types were similar.The relative-abundance of certain COG genes was different.For some COG genes,such as COG1309,COG1595,COG1846,etc,their relative abundances were higher than those of the control.In the soils treated with polyoxins and mancozeb,the relative abundance of COG gene types(C,E,G,I,K,M,P,R,S and T)increased comparing with the data before the experiments,and was higher than that in the control soil.In the culture-dependent experiments,the fungicides affected the colony forming units(CFUs)of actinobacteria with the lower CFUs comparing to the control.The number of actinobacterial isolates was lower at the beginning of experements treated by thiophanate-methyl/Thiram and mancozeb,and increased in the subsequent investigations.The opposite results were observed in the polyoxins-treated soils.A total of 216 actinobacterial isolates were obtained from the soil samples,and were assayed for their antagonistic activities with the pathogenic fungi –Fusarium solani,F.oxysporum,Phomaher barum and Plectosphaerella cucumerina.Twenty-seven isolates presented antimicrobial activity against at least one of tested pathogens,which is helpful for the collection of potential biocontrol microbes.Among the culturable isolates,isolate YIM PH21723 were designated a novel species of genus Umezawaea,U.notoginseng sp.nov.on the basis of the polyphasically taxanomic experiments.