Helper bacteria associated with Casuarina cunninghamiana-Frankia symbiosis: Selection of isolates for their effects on plant growth in axenic conditions

Abstract

The formation of Casuarina actinorhizae in axenic conditions remains a challenge hindering research program. To explore the putative role of helper bacteria favouring actinorhizae formation, 50 bacteria were tested in an original selection scheme for their effects on C. cunninghamiana growth in the presence of Frankia. Two strains FAB1 and FAB2 were identified as having a significant promoting effect on C. cunninghamiana growth in the presence of Frankia. Actinorhizae formation was never observed in these strictly axenic conditions. The comparison of 16S rDNA sequences shows similarity of 99% for FAB1 with Bacillus sp. and of 99% for FAB2 with Ochrobactrum sp. © 2004, Taylor & Francis Group, LLC.