Rhizosphere Microbial Diversity Of Achyranthes Bidentata And Control Of Peanut Southern Blight By Biocontrol Actinomyces

Plant rhizosphere microorganisms are a class of microorganisms colonized in plant roots.Due to the influence of plant secretions,the content of microorganisms is much higher than that in conventional soil,and the secondary metabolites have a wide variety and high biodiversity,which are important resources for screening new active substances.Peanut southern blight is a fungal disease which is caused by the pathgen Sclerotium rolfsii Sacc.,and seriously restricts the quality and yield of peanut.This paper took three pieces of Wuzhi County planting site of Achyranthes bidentata in Jiaozuo,Henan Province,rhizosphere soil samples of Achyranthes bidentata were collected by five-point sampling method;High throughput sequencing technology was used to study the rhizosphere soil microbial diversity of Achyranthes bidentata;Actinomyces rhizosphere was isolated by plate dilution method;The plate confrontation method was used to screen and identify the actinomyces that had antagonistic effect on the microkaryotes;The effect of aseptic fermentation filtrate on mycelium growth rate of sclerotinomycetes and six common pathogenic fungi was studied by mycelium growth rate method;The effect of antagonistic actinomycetes aseptic fermentation filtrate on sclerotinia formation and sclerotinia germination was observed;The control effect of antagonistic actinomycetes fermentation broth on peanut southern blight and its growth promotion effect on peanut were determined by pot experiment in greenhouse,and the growth promotion function of antagonistic actinomycetes was analyzed.The main contents and results are as follows:1.High throughput sequencing technology was used to study the rhizosphere microbial diversity of Achyranthes bidentata at three sampling sites.Among them,Achyranthes bidentata plants in sampling sites 1 and 2 were larger and had similar growth,while those in sampling sites 3 were smaller.Alpha diversity analysis showed that the rhizosphere microbial abundance and diversity in sampling sites 1 and 2 was higher than that in sampling sites 3,and Beta diversity analysis showed that the community composition was different among the three treatments.At the phylum level,Proteobacteria,Frimicutes and Actinobacteriota were the dominant bacteria in the three treatments.The relative abundance of Proteobacteria is higher in Soil₁,49.31% in Soil₂ and 71.70% in Soil₃ than in Soil₁ and Soil₂.At the genus level,relative abundance of the genus Unclassified_f<sub>Erwiniaceae in Soil₃ was 38.64%,far higher than 0.10% and 1.93% of Soil₂ and Soil₁.In Soil₁,there were 5 genera with relative abundance above 3%,in Soil₂,there were 5 genera with relative abundance above 3%,and in Soil₃,there were 3 genera with relative abundance above 3%.The results of functional analysis showed that the functions of bacteria in rhizosphere soil concentrated on chemoheterotrophy and aerobic chemoheterotrophy.2.A total of 116 strains of actinomyces were isolated from rhizosphere Soil of Achyranthes bidentata,and two dominant actinomyces soil-1-5 and soil-3-28 were selected according to the persistence of antibacterial activity and the strength of antibacterial activity through plate face-off culture with 7 plant pathogens such as Sclerotium rolfsii Sacc.The inhibition rates of the bacteria were 92.34% and 80.43%,respectively.Physiological and biochemical identification,morphological characteristics observation and molecular biological identification identified Soil-1-5as Streptomyces scabiei and Soil-3-28 as Streptomyces luteogriseus.3.Determination of antagonistic actinomycetes cell-free fermentation filtrate to Sclerotium rolfsii Sacc.mycelium growth rate,sclerotium formation,the influence of sclerotium germination,as well as the antagonistic actinomycetes cell-free fermentation filtrate bacteriostatic spectrum evaluation.The results showed that the two strains could inhibit the growth of mycelia.When the cellless fermentation filtrate was diluted 5times,the inhibition rates of Soil-1-5 and Soil-3-28 on mycelia growth were 73.67%and 57.11%,respectively.The results of sclerotium formation test showed that the cellless fermentation filtrates of Soil-1-5 and Soil-3-28 had antagonistic effect on sclerotium formation,and the inhibition rates of the number of sclerotium and the weight of sclerotium were 78.08% and 50.68%,respectively,and 41.86% and 34.68%,respectively.When the sclerotium was inoculated into the plate containing the antagonistic cellless fermentation filtrate,it was found that the germination of sclerotium was inhibited.The inhibition ratio of Soil-1-5 and Soil-3-28 on the germination of sclerotium was 34.87% and 50.19% when cultured for 24 h.The inhibition rate of the two strains on sclerotium germination increased to more than 40%,and the overall inhibition effect on sclerotium germination was first enhanced and then weakened.4.The inhibitory effect of antagonistic actinomycetes aseptic fermentation filtrate on 6 plant pathogenic fungi was determined.The results showed that the two strains of aseptic fermentation filtrate could inhibit the mycelium growth of 6 pathogenic fungi.The inhibition rate of Soil-1-5 on pathogenic fungi ranged from 84.24% to 16.67%,and the inhibition rate of Ceratobasidium graminearum was the strongest,with a bacteriostasis rate of 84.24%.Soil-3-28 had the highest inhibition rate of pathogenic fungi from 34.55% to 16.15%,and also had the strongest inhibition rate of Ceratobasidium graminearum（34.55%）.5.The control effect of antagonistic actinomycetes fermentation broth on peanut southern blight was determined by pot experiment in greenhouse.The results showed that Soil-1-5 and Soil-3-28 could reduce the incidence of peanut southern blight,and the control effects were 51.92% and 31.74%,respectively.6.The growth-promoting effect and potential activity of Soil-1-5 and Soil-3-28 fermentation liquid on peanut were determined by pot experiment under greenhouse conditions.The results showed that Soil-3-28 had significant growth promoting effect on peanut plants,and all the measured indexes were significantly higher than the control.Through exploring its growth promoting function,the results showed that Soil-3-28 had potential growth promoting activities such as phosphorus solubilization,ammonia production and IAA production.Soil-1-5 fermentation liquid irrigation had no significant effect on peanut growth.These results indicated that higher rhizosphere microbial community diversity and richness was conducive to the growth of achyranthes bidentata.Two strains of antagonistic actinomycetes isolated from rhizosphere Soil of Achyranthes bidentata showed strong inhibition on mycelium and sclerotia of Sclerotium rolfsii Sacc.,and soil-1-5 and Soil-3-28 could be used as effective strains to control peanut southern blight.