Primary research on the isolation method of root endophytic bacteria of Cymbidium goeringii

This paper studies the optimal surface sterilization condition of Cymbidium goeringii Rchb.f.roots and their effect on endophytic bacteria isolated by eight media.The 8 media include Modified czapek agar,Starch-ammonium nutrient agar,YG medium,R2A medium,Luria-Bertani medium(LB),King's medium B(KMB),Tryptic Soy Agar(TSA) and Root exudate medium.The results indicate that conditions for best surface sterilization were: roots washed with 75% ethanol for 3 min,immersed in fresh sodium hypochlorite solution(3% available Cl-) for 2 min,rinsed with 75% ethanol for 30 s,and finally washed with sterile distilled water.There were certain differences among the endophytic bacteria isolated by using different media.CFU on R2A medium and root exudate medium outnumbered that on the other media,and the most kinds of endophytic bacteria were found on YG and R2A media.16S rDNA sequences of representative strains from different media showed high similarity with Rhizobium spp.,suggesting that the eight media had the same effect on the isolated dominant endophytic group.The results may contribute to isolation of orchid endophytic bacteria by using proper medium.