Screening And Identification Of Seven Antagonistic Strains Against Phytopathogens Of Panax Ginseng And Preliminary Evaluation Of Their Antifungal Effect

Panax ginseng C.A.Meyer belongs to the Araliaceae family and is one of the most valuable traditional Chinese herbal medicines.Ginseng cultivation in our country gets the first place around the world and Changbai Mountains,Jilin province is the main ginseng production region in China.One ginseng cultivation cycle generally needs 5 to 6 years.Long time monoculture of P.ginseng resulted in problems including the degradation of soil physical and chemical characteristics,the change of microbial community,multiple diseases etc.Serious diseases problems have influence on the yield and quality significantly,traditional chemical control strategy usually resulted in the excessive pesticide residues,which have threaten to environment,ecology,and the healthy of human and stocks around.Biological control has many advantages,such as environmental friendly,fast control effect and lasting etc.,and without pesticide residues.In the present work,strains shown significant antagonistic activity against pathogens of P.ginseng were isolated from ginseng cultivating soil and commercial biocontrol agents.Taxonomies of these strains were identified through ribosomal DNA-ITS sequencing,morphology observation and physiological and biochemical indexes analysis.Furthermore,the controlling effects of these antagonistic strains were evaluated by the field cultivation test,Preliminary studies and reasonable interpretation on the antagonist mechanism of them via laboratory research,which provided good foundation for the development of microbial agents and further antagonistic mechanism research.All the results were listed as following:1.In total,83 stains were isolated.66 strains out of them were from ginseng cultivated soil,while 17 strains out of them were from commercial microbial agents.Among of them,strains QM,BM2,HZ3,GG,X,HC and DD have antagonistic activity against pathogens of P.ginseng,Fusarium solani,Cylindrocarpon destructans,Alternaria panax and Botrytis cinerea.Based on homology analysis,microscopic observation,and physiological and biochemical indexes determination,strains QM,BM2 and HZ3 were identified as Bacillus methylotrophicus,GG was identified as B.subtilis,X was identified as B.amyloliquefaciens,HC was identified as Trichoderma asperellum and DD was identified as T.effusum.2.In total,12 treatments including single strain,5 bacteria mixture,2 fungi mixture,7 strains mixture and controls were set in the field experiment.We found that,except for BM2,the ginseng emergence rate of each treatment was higher than positive control of pesticide carbendazol and negative control of H2O.The ginseng seedling survive rate of each strain treatment was similar to positive control of pesticide carbendazol and higher than negative control of H2O.Seven strains had shown no harmful to the growth of ginseng seedlings.3.When confront culture 7 strains with pathogens of P.ginseng,obvious inhibition zone were generated.Through optical microscope and electron microscope observation we found that,mycelia of pathogens confront cultured with antagonists shown abnormal growth compared with control,and which were closely related to the antagonistic effects of 7 strains.4.The fermentation broth and the fermentation supernatant of QM,BM2 and HZ3 inhibit the growth of ginseng pathogens significantly.Active substances in the supernatant were extracted respectively and we found that crude lipopeptid,crude protein and water-saturated-butanol extracts shown antagonistic activity at different levels,which suggest that there are various antagonistics in extracellular secretions,and these active substances inhibited the growth of pathogens of P.ginseng individually or synergistically.