Community Diversity Of Endophytic Bacteria Of Cymbidium Goeringii And Screening Of Functional Strains

In this study, the diversity of endophytic bacteria in the roots of wild Cymbidium goeringii was investigated by culture-dependent method and construction of 16S rDNA clone library. siderophore-producing and antagonist bacteria were screened from C. goeringii endophytic strains isolated in our laboratory.A total of 63 strains were isolated from the roots of the wild C. goeringii. The diversity of the culturable endophytic bacteria was analyzed by the amplified DNA restriction analysis (ARDRA) and 16S rDNA sequence analysis. The results showed that 63 strains belonged to 5 genera of proteobacteria (Betaproteobacteria, 31.75%; Gammaproteobacteria, 7.94%), Firmicutes, 60.31%); and the dominant genus was Bacillus. There may be one novel taxonomic unit.The phylogenetic analysis of 16S rDNA clone library of endophytic bacteria in the roots of wild C. goeringii revealed that 188 positive clones belonged to proteobacteria(Alphaproteobacteria, 5.85%; Betaproteobacteria, 63.30%; Gammaproteobacteria, 7.98%; Deltaproteobacteria, 1.06%), Bacteroidetes(9.57%), Firmicutes(4.79%), Actinobacteria(1.60%), Acidobacteria(0.53%), and Ktedonobacteria(1.06%). Eight clones could not be identified. The dominant phylogenetic group was proteobacteria(78.19%), Burkholderia was the dominant genus. The results suggested that the diversity of endophytic bacteria in C. goeringii roots obtained by the clone library was more abundant than it obtained by culture-dependent method.Forty-seven siderophore-producing bacteria were screened from root endophytic strains of C. goeringii by using chrome azurol S (CAS) agar plate assay. The diversity of siderophore-producing endophytic bacteria was investigated by 16S rDNA sequence analysis. Sequence analysis revealed that 47 strains belonged to 17 generas of proteobacteria (Alphaproteobacteria, 17%; Betaproteobacteria, 23.4%), Firmicutes, 17.0%, Actinobacteria, 42.6%. The dominant genera were Bacillus and Variovorax, and the strains of Variovorax produced relatively high levels of siderophore. In addition, there might be two novel taxonomic units. The results showed that there was abundant species diversity of siderophore-producing endophytic bacteria in the roots of C. goeringii. It was the first report Nocardioides, Nocardiopsis, Solirubrobacter, Sphingopyxis, Pannonibacter, and Alterierythrobacter were isolated as siderophore-producing endophytic bacteria.Among 459 endophytic strains isolated from the C. goeringii, strain gt19-1 with high activity to inhibit the Colletotrichum gloeosporioides Penz was screened by plate antagonistic method. According to morphological observation, physiological characteristics tests, and 16S rDNA sequence analysis, gt19-1 was identified as a strain of Bacillus subtilis. Both the sterile fermentation broth and crude protein of strain gt19-1 could inhibit C.gloeosporioides Penz; whether there are other antibacterial substances in the sterile fermentation broth, it is still needed to study in the future. The greenhouse control effect experiment showed that strain gt19-1 had biocontrol effect on the pepper anthracnose, the control efficacy was 22%.