Studies On Antimicrobal Activity Of Two Strains Of Endophytic Fungi From Ginkgo Biloba

The purpose of this experiment is to screen active endophytic fungi strains fromthe Ginkgo biloba which have practical value.This will provide material for furtherextraction of active secondary metabolites, and establish a basis for the developmentand utilization of the active endophytic fungi. The main results are as follows:1)451endophytic fungi were isolated from different parts of the ginkgo such asthe roots, branches and leaves,99strains isolated from roots,245from branches,117from leaves.9pathogenic bacteria and12fungal pathogens in agriculture were as thetest target strains to screen active endophytic fungi. A total of33endophytic funguswith antimicrobial activity was screened. M13and M50were obtained ultimatelyfrom the further screening of33endophytic fungal fermentation. M13and M50haverespectively broad-spectrum inhibition for pathogenic bacteria and pathogenic fungi.2) The fermentation broth of M13strain has great and stable antimicrobialactivity. Salmonella typhi18mm, Bacillus subtilis30mm, Erwinia amylovora26mm,Staphyloccocus aureus18mm, Pseudomonas solanacearum18mm, Acidovoraxavenae18mm, and Escherichia coli22mm. Among those pathogenic bacteria, theinhibition for Bacillus subtilis was the best, which inhibition zone diameter was up to30mm.3) The fermentation broth of M50strains has wide antifungal range,includingRhizoctonia solani, Sclerotinia sclerotiorum, Magnaporthe oryzae, Alternarialongipes, Fusarium graminearum, Sclerotium rolfsii, Botrytis cinerea, Fusariumsolani, Colletotrichum micotianae, Colletotrichum higginsianum, Phytophthorainfestans.The inhibition rate were91.2%,91.6%,100%,71.4%,80.9%,63.2%,82.6%,45.5%,84.4%,77.1%and58.3%, respectively. The inhibition rate of the lowest was45.5%up to100%, the highest was100%. The inhibition effect was significant.4) M13crude extract (1mg/mL) has inhibition activity for Escherichia coli,Bacillus subtilis, Erwinia amylovora and Staphyloccocus aureus. Their inhibitionzone sizes were respectively18mm,32mm,31mm,32mm. The relativechloramphenicol biological potency of M13fermentation broth used Staphylococcusaureus as reference bacteria was4.01mg/ml.5) The inhibition effect of M50crude extract (10mg/mL) was good against thetested pathogenic fungi. It has different degrees of inhibition for Rhizoctonia solani,Sclerotinia sclerotiorum, Magnaporthe oryzae, Phytophthora infestans, Fusarium graminearum, Sclerotium rolfsii, Botrytis cinerea, Fusarium solani, Colletotrichummicotianae, Colletotrichum higginsianum, Alternaria longipes. Compared with thetwo positive control of the Actidione and Kresoxim, M50crude extract had a strongerantibacterial activity for Magnaporthe oryzae, Alternaria longipes, Colletotrichumhigginsianum, Phytophthora infestans, Sclerotium rolfsii, Sclerotinia sclerotiorum,Rhizoctonia solani. The range of crude extract is consistent with of fermentationbroth.6) Combined with the results of morphological identification and18S rDNAand ITS molecular identification to determine the taxonomic status of the M13, M13was identified as, Imperfecti fungi, Moniliales, Tuberculariaceae, Fusarium,Fusarium oxysporum.7) Conidia morphology of M50was broom. M50can not be determined from18S rDNA and ITS sequences and Morphological characteristics. M50may be a newspecies, but needs further study.