Screening, identification and bacteriostasic activity of antagonistic endophytic bacteria against Rosa chinensis Jacp.anthracnose

【Objective】To explore the resources of endophytic antagonistic bacteria of Rosa chinensis Jacp., and provide efficient and stable antagonistic strain resources for biocontrol of R. chinensis anthracnose. 【Method】The leaves of 20 healthy and disease-free Rosa species were used as test materials, the endophytic bacteria were isolated from the leaves by tissue homogenization method, the endophytic bacteria strains with antagonistic effect against Colletotrichum fructicola YJY-20 were screened by plate confrontation method. The antagonistic bacteria were identified according to colony morphology, physiological and biochemical characteristics and 16S rRNA sequence analysis. The antagonistic effect against C. fructicola YJY-20 of volatile organic compounds from antagonistic bacteria were determined by plate interlocking method. The inhibitory activity of sterile fermentation broth of the antagonistic bacteria on C. fructicola YJY-20 and its hyphae were determined by the Oxford cup diffusion method. The PCR was used to amplify lipopeptide biocontrol functional genes. The inhibitory activity of the crude protein and lipopeptide antibacterial substance from antagonistic bacteria against C. fructicola YJY-20 were determined by agar well diffusion method. The extracellular enzyme activity of the antagonistic bacteria were detected by plate assay method. The inhibitory activity of antagonistic bacteria against 12 different plant pathogenic fungi were determined by plate confrontation method. The control effects of fermentation broth of antagonistic bacteria against R. chinensis anthracnose caused by C. fructicola were detected by in vitro leaves experiment. 【Result】Two endophytic bacteria strains DMGSMG4 and QZM1 with strong activity against C. fructicola YJY-20 were isolated and screened from the leaves of Rosa species, and they were identified as Bacillus amyloliquefaciens and B. velezensis respectively. The inhibition rates against C. fructicola YJY-20 of strains DMGSMG4 and QZM1 volatile organic compounds were 11.72% and 30.71% respectively, and they both could reduce melanin production of C. fructicola YJY-20.The inhibition rates against C. fructicola YJY-20 of strains DMGSMG4 and QZM1 sterile fermentation broth were 60.25%and 61.24% respectively, and they could cause hyphae of C. fructicola YJY-20 breakage and distortion. The inhibition rates against C. fructicola YJY-20 of strains DMGSMG4 and QZM1 crude protein were 59.76% and 50.63% respectively, and their thermal stability was good. The inhibition rates of the strains DMGSMG4 and QZM1 lipopeptide antibacterial compounds on C. fructicola YJY-20 were 50.07% and 45.03% respectively. The two strains both could amplify lipopeptide antibacterial substance synthetic related genes such as srfAA, srfAB, fenD and bmyB. The two strains both could produce cellulase and protease, and strain DMSGMG4 could produce organic acids. The inhibition rates of two strains DMGSMG4 and QZM1 were more than 50.00% against 12 different plant pathogenic fungi, and control rates on the in vitro leaves with anthracnose were 59.35% and 20.58% respectively. 【Conclusion】The screened strains DMGSMG4 and QZM1 have strong antagonistic effect against C. fructicola, and they show potential to be biocontrol strains for R. chinensis anthracnose.