Rhizoplane colonisation of peas by Rhizobium leguminosarum bv. viceae and a deleterious Pseudomonas putida

Pseudomonas putida strain Å313, a deleterious rhizosphere bacterium, reduced pea nitrogen content when inoculated alone or in combination with Rhizobium leguminosarum bv. viceae on plants in the presence of soil under greenhouse conditions. When plants were grown gnotobiotically in liquid media, mixed inocula of Å313 and rhizobia gave a higher proportion of small evenly distributed nodules when compared with a single rhizobial inoculation. In addition, the rhizobial root establishment was reduced by Å313 irrespective of inoculum density, indicating that Å313 has the capacity to interact with the early rhizobial infection process. When pea seedlings were simultaneously inoculated with Å313 and rhizobia, Å313 colonised the root hairs to the same extent as the rhizobia, according to analysis by immunofluorescence microscopy. This suggests that the root hair colonisation trait of P. putida interferes with the onset of the symbiotic process.