Construction Of Astragalus Root Artificial Microflora And Its Potential For Controlling Root Rot

Astragalus membranaceus(Fisch.)Bge.var.mongholicus(Bge)Hsiao is a kind of bulk Chinese herbal medicine with a large market demand,but in the process of artificial cultivation,it is easy to be infected with various diseases,among which root rot is particularly serious.In order to control the incidence of Astragalus mongholicus Bunge root rot and improve its medicinal quality,we first analyzed the diversity of Astragalus mongholicus Bunge roots microbes.Then based on the healthy and diseased Astragalus mongholicus Bunge roots' differential microorganisms and key microorganisms,we constructed a synthetic flora and explored the effect of the synthetic flora on the prevention of Astragalus mongholicus Bunge root rot.The main results are as follows:(1)A total of 694 strains of bacteria were isolated from Astragalus mongholicus Bunge root and rhizosphere soil.After 16 S r DNA gene sequence analysis,the same strains were combined to obtain 423 strains,belonging to 74 genera,of which Pseudomonas(12.09%),Microbacterium(11.85%),Bacillus(11.14%),Rhizobium(6.40%),Streptomyces(6.16%)accounted for a large proportion.53 fungi were isolated from the roots of Astragalus mongholicus Bunge,and ITS gene sequence analysis showed that 53 fungi came from 16 genera,of which Aspergillus(20.75%),Fusarium(16.98%),and Talaromyces(11.32%)accounted for a large proportion.(2)Among the 53 fungi,there are 11 potential plant pathogens.Inoculated these 11 strains into Astragalus mongholicus Bunge and found that the plants inoculated with Fusarium oxysporum had a higher incidence of 77.00%.Fusarium oxysporum was considered to be the pathogenic fungus of Astragalus mongholicus Bunge root rot.Taking Fusarium oxysporum as the indicator bacteria,34 strains with antagonistic effect on Fusarium oxysporum were screened through the plate confrontation experiment,of which 9 strains had very significant antagonistic effects on pathogenic bacteria.These 9 strains were inoculated into Astragalus mongholicus Bunge to explore their control effect on Astragalus mongholicus Bunge root rot.The strain J-1(Bacillus velezensis)was found to reduce the morbidity and lethality of Astragalus mongholicus Bunge root rot by 34.15% and 59.06%,with the best disease resistance.(3)We conducted high-throughput sequencing of the microbial community in the Astragalus mongholicus Bunge root area.Through analysis of the sequencing data,it was found that the abundance of Microbacterium?Sphingopyxis and other genus bacteria in the surrounding soil of diseased Astragalus mongholicus Bunge root was significantly increased.In rhizosphere soil,the abundance of bacteria genus Flavobacterium?Tumebacillus?Pseudomonas? Sphingobium was significantly increased,and in the root,the abundance of strains of genus Achromobacter?Flavobacterium? Phyllobacterium?Pseudomonas etc.was significantly increased.The characteristics of phosphorus dissolution and potassium dissolution and IAA production of 422 isolates were measured respectively.With the help of microbial diversity data,two synthetic bacterial groups were constructed,namely,flora 1(Microflora with significantly increased abundance in the root area of diseased Astragalus mongholicus Bunge.)and flora 2(Microflora with significantly decreased abundance in the root area of diseased Astragalus mongholicus Bunge).Inoculate the Astragalus mongholicus Bunge with flora 1 and flora 2 respectively,and compare the growth promotion and disease resistance characteristics of the two synthetic bacteria groups to Astragalus mongholicus Bunge.The results showed that the root length and plant height of Astragalus mongholicus Bunge in the treatment flora 1 were significantly higher than those in the treatment flora 2 and the blank control group,and the root lengths were 54.33% and 70.50% higher than those of the other two groups,and the plant heights were 20.56% and 34.48% higher.The morbidity of Astragalus mongholicus Bunge in the treatment flora 1 was also significantly lower than that in the other two groups,which were 34.31% and 26.32% lower than those in the treatment flora 2 and control group,respectively.(4)Select the flora 1 and the single-infected bacteria J-1,inoculate into Astragalus mongholicus Bunge.The results showed that the morbidity of the treatment flora 1 were significantly lower than that of the single-inoculation J-1,which was 7.41% lower than that of the J-1 treatment group.The root length and plant height of the treatment flora 1 were 36.04% and 44.65% higher than those of single inoculation J-1,indicating that the bacterial flora 1 we constructed has good growth promotion and disease resistance effects on Astragalus mongholicus Bunge..