Study On Isolation, Identification And Genetic Diversity Of Pseudomonas Fluorescens

One hundred and four Pseudomonas fluorescens strains isolated from the rhizosphere of twelve plants growing at some different sites in shanghai were identificated by phenetic classification and characterized by REP-PCR, PCR-RFLP of 16SrDNA.16S rDNA PCR-RFLP cluster analysis and REP-PCR cluster analysis indicated that there is a great genotypic diversity of Pseudomonas fluorescens. Seventeen 16S rDNA genotypes(l-17)were detected, and 50% of srains were genotype 1. Among the 5 restriction enzymes used, HaeIII. and Hinf I were the most discriminating enzymes. The multiple tree can indicate more difference between specieses and strain's idiosyncrasy. At the 85% and 76% similarity level, 16S rDNA PCR-RFLP dendrogram and REP-PCR dendrogram were composed of 9 and 26 groups respectively. The strains belonged to one phenon in the 16S rDNA PCR-RFLP taxonomy distributed into several REP-PCR groups. These results showed that REP-PCR fingerprinting is an effective method to study the diversity in the interior of one species, and REP-PCR fingerprinting also had higher resolution. The dendrogram constructed using 16S rDNA PCR-RFLP and REP-PCR fingerprints grouped the strains mainly according to their geographical and cultivar origions. Inaddition, there was a great genotypic diversity among some Pseudomonas fluorescens isolated from the same geographical or cultivar origions. The result above showed that there was a great genotypic diversity and phylogenetic diversity among the isolated Pseudomonas fluorescens.In summary, the paper disclosed a great diversity of the Pseudomonas fluorescens strains in the aspects of phenotypic and genotypic characteristics. The gene stock of Pseudomonas fluorescens diversity was enriched. The Pseudomonas fluorescens resources were provided on breeding excellent strains. The base was also established on further studying taxonomic position of Pseudomonas fluorescens isolated from plants in shanghai region.