Endophytic Pseudomonas spp. populations of pathogen-infected potato plants analysed by 16S rDNA- and 16S rRNA-based denaturating gradient gel electrophoresis

The diversity of abundant and metabolically active pseudomonads in potato plants was analysed using a culture-independent approach. The effect of two plant varieties, Agria and Bionta, as well as the presence of a plant pathogen Erwinia carotovora ssp. atroseptica on this bacterial group was tested. A combination of Pseudomonas-specific PCR, DGGE analysis, cloning and sequencing of partial 16S rDNA genes was performed using DNA and RNA extracted from potato stem tissue. Sequence analysis revealed a high species diversity, with the most prominent ones being Pseudomonas stutzeri and Pseudomonas gingeri. Some species showed high rRNA contents indicating high metabolic activity. Both, highly abundant and metabolically active Pseudomonas populations were more affected by the plant genotype than by the presence of E. carotovora.