Diversity Of Actinobacterial Community In The Planting Soil Of Panax Notoginseng

Radix notoginseng is a traditional Chinese medicine only distributing in China,with high pharmaceutical and economical values.Panax notoginseng grows in a rigorous ecological environment,including special soil properties and climate.The growth period of P.notoginseng is quite long as 3-5 years within a no-tillage soil.Another question-replanting obstacle is obvious and very difficult to overcome.Successfully replanting notoginseng needs at least 20 years interval.Changes in the soil microbiome,especially the breeding and increasing of pathogens,are considered as a primary cause for the continuous cropping obstacle.Actnio bacteria is an important taxonomic group in the soil microbio me,and play key roles in preventing and controlling diseases in agronomy.However,little is known about the actinobacteria associated with the notoginseng.Therefore,we carried out investigations on the diversity and community,together with the changes of actinobacteria in the soil planting with notoginseng using culture-and uncultured-dependent methods(MiSeq).The challenging activities against the main pathogens of notoginseng were developed using the obtained actinobacterial isolates.The effects of 10 common applied pesticides on the actinobacterial strains were also evaluated in this report.The results is helpful to understand the ecological roles of actinobacteria in the growth of notoginseng.The results obtained by MiSeq sequencing presented that actinobacteria in the bulk soil(without notoginseng plants)were assigned to 8 orders,44 families,and 115 genera.At the family level,Nocardioidaceae?Pseudonocardiaceae?unclassified group were the dominant groups,while unclassified group and Mycobacterium with high abundance at the genus level.There was no obvious change at the taxonomic levels in the bulk soil.Actinobacteria in the planting notoginseng soil were assigned to 8 orders,45 families,and 117 genera.At the family level?Nocardioidaceae?Pseudonocardiaceae?unclassified group were the dominant groups,while unclassified group and Mycobacterium with high abundance at the genus level.The abundances of Thermoleophilales and Thermoleophilaceae in notoginseng soil significantly decreased compared with that in bulk soil.The abundances of Nocardioidaceae and Streptomyceteae in the first stage soil after planting notoginseng plants was higher than that in the bulk soil,and decreased with the growth of notoginseng.The same trend was observed in the abundances of Nocardioides and Marmoricola,belonging to Nocardioidaceae,and Streptomyces belonging to Streptomycetaceae.However,the unclassified groups with high proportion increased slightly as the growth of notoginseng.Four hundred and forty six actinobacterial isolates were obtained by culture-dependent method.The isolates were assigned to 7 orders,8 families and 10 genera.Streptomyces still is the dominant group in all tested samples with a high proportion of 79%.In the pure cultures,the numbers of actinobacteria in all soil samples(plant soil and bulk soil)presented the increasing at the first stage and decreasing in the following stages,while no obvious change was observed in term of Streptomyces.The antagonistic activities of all the actinobacterial isolates against the causative pathogens were screened with Fusarium solani?Epicoccum nigrum?Phoma herbarum?F.oxysporum?F.flocciferum?Alternariapanax?Plectosphaerella cucumerina,using the confrontation culture and agar diffusion methods.Twenty eight isolates showed antagonistic activities against all the test pathogens at different degrees.Among them,isolate PH21294(Streptomyces spiroverticillatus)presented the strongest inhibition against A.panax with an inhibitory zone diameter of 40 mm,inferring its potential in the biological control of root rot of notoginseng.The effects of 10 pesticides commonly used in the notoginseng on the active isolate PH21294 were evaluated with the biomass tests.At low concentrations(0.1?g/mL),9 pesticides could promote the growth of S.spiroverticillatus PH21294,and the biomass was 6 times comparing to the control while grown in the medium with 0.1?g/mL thiophonate-methyl/mancozeb.The growth of S.spiroverticillatus PH21294 was totally inhibited at high concentrations of 7 pesticides,50 ?g/mL thiophonate-methyl/thiram,50 ?g/mL mancozeb,110 ?g/mL iprodione,110 ?g/mL methidathion,110?g/mL cypermethrin/malathion,330?g/mL polyoxins,and 330 ?g/mL thiophonate-methyl/mancozeb.However,procymidone could still promote the growth of S.spiroverticillatus PH21294 at a high concentration of 330 ?g/mL.