Screening,antagonistic mechanism of antagonistic endophytic bacteria against root rot of Paeonia lactiflora
[Objective]This study provides microbial resources and theoretical basis for the biological control of peony root rot.[Method]The root tissues of healthy peony were collected from the growing area of peony in Luoyang,endophytic bacteria were isolated from the root tissue of healthy peony by surface disinfection method and tissue grinding method,endophytic bacteria antagonizing pathogens of peony root rot were screened by plate confrontation,and antagonistic bacteria were identified by morphological characteristics,physiological and biochemical property and molecular biological methods.PCR amplified three lipopeptide synthesis genes fenA,srfAA and ituD of the antagonist strain.Acid precipitation and methanol extraction method were used to extract liptide substances from antagonistic strains,and the effect of liptide substances on the morphology of pathogenic bacteria was observed.The expression levels of fenA,srfAA and ituD genes were analyzed by RT-QPCR when antagonistic strains confronted with pathogen of peony root rot.[Result]Endophytic bacteria H35 had a good antagonistic effect on pathogen of peony root rot,and the inhibitory rate of its fermentation liquid was 62.5% .Based on morphological characteristics and 16s DNA sequence analysis,strain H35 was identified as Bacillus velezensis.PCR amplification showed that strain H35 could amplify the corresponding lipopeptide synthesis gene,and the inhibitory rate of the extracted lipopeptides against pathogen of peony root rot was 73.8%,and lipopeptides had a strong teratogenic effects on hyphae of pathogen.The results of quantitative real-time PCR showed that the relative expressions of fenA,srfAA and ituD genes of strain H35 were up-regulated when it was co-cultured with pathogens,and the expression of ituD gene was significantly higher than that of control.[Conclusion]The strain H35,exhibiting strong antagonistic activity against peony root rot pathogen,is isolated from the root tissue of healthy peony plants and identified as B.velezensis;The strain H35 has the ability to synthesize lipopeptides and induce distortion in the mycelia of the root rot pathogen.
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