Effects of culture filtrates of rhizobacteria isolated from wild lupine on germination, growth, and biological nitrogen fixation of lupine seedlings

In order to select potential Plant Growth Promoting,Rhizobacteria (PGPRs), a selection of strains from the predominant genera in the rhizosphere of four lupine species, based on genetic divergence criteria, carried out in a previous study, yielded 11 Aureobacterium (Aur), four Cellulomonas (Cell), two Arthrobacter (Arch), two Pseudomonas (Ps), and six Bacillus (Be) strains. Cell-free culture filtrates of each bacterium were assayed for effects on germination, growth, and biological nitrogen fixation (BNF) of Lupinus albus L. ev. Multolupa seeds or seedlings. Four (Aur 6, Aur 9, Aur 11, and Cell 1) of the twenty-five strains assayed promoted germination. Aureobacterium 6 and Aur 9 also increased root surface, total nitrogen content, and BNF As a result of the screening, and considering all the variables studied, Aur 6 can be considered a plant growth promoting rhizobacterium and is suitable for further field trials in other plants and in different production systems.