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A screening for Plant Growth Promoting Rhizobacteria (PGPR) was carried out in the rhizosphere of wild populations of Nicotiana glauca Graham in south-eastern Spain. Nine hundred and sixty strains were isolated and grouped in four parataxonomic groups: Gram positive endospore forming bacilli, Gram positive non-endospore forming bacilli, Gram negative bacilli and others. Two groups were selected to continue the study: Gram negative bacilli since it was the most abundant, and Gram positive sporulated bacilli, seeking their sporulating capacity as an advantage for inoculants formulation. The ability of these to release siderophores and chitinases in vitro was evaluated. Ninety six isolates were siderophore producers, and 56 of them were also able to produce chitinases. Fifty percent of these were tested for growth promotion in tomato. The best results were obtained with 5 Gram negative bacilli and one Gram positive sporulated bacilli; 5 strains increased all growth parameters while one of them, N21.4, severely compromised plant growth. The ability of these 6 strains to induce systemic resistance against the leaf pathogen Xanthomonas campestris in tomato was evaluated. Five of them effectively reduced disease symptoms (up to 50%). The six strains were identified by 16s rDNA sequencing resulting in 3 Pseudomonas, 1 Bacillus and 2 Stenotrophomonas; it's striking that 2 Pseudomonas protected up to 50% while the other increased disease incidence. This indicates that systemic induction is strain specific and not necessarily related to production of siderophores and chitinases.

Nine plant growth-promoting rhizobacteria from different backgrounds were assayed on Glycine max var. Osumi to evaluate their potential as biotic elicitors to increase isoflavone (IF) levels. Strains were inoculated on 2 day old pregerminated seeds. Six days after inoculation, the seedlings were harvested. Biometric parameters were registered, and IFs were determined. Although only one strain (N21.4) increased total IF contents and only one (M84) caused significant decreases in total IF, five different behaviors were detected when the daidzein and genistein families were analyzed separately. All strains triggered IF metabolism so further studies have to be developed since the different beneficial effects of IF through the diet may be due to the different IF profiles. These are encouraging results from two points of view: (1) N21.4 increases IF in seedlings, and (2) all other beneficial strains trigger IF metabolism differentially; hence, both facts could be used to prepare food supplements or as enriched standardized foods after full development of the biotechnological procedure.

Aims: A structural and functional study has been carried out in the rice production area of the Guadalquivir marshes in southern Spain aiming to increase knowledge of rice rhizosphere structure and function for further application on integrated management practices. Methods and Results: Rhizosphere bacterial structure (analysis of 16S rRNA partial sequences from total soil DNA), metabolic diversity (analysed by Biolog FF for fungal community and GN for microbial community) and a screening for putative plant growth-promoting rhizobacteria (PGPR) to identify potential isolates for development of local biofertilizers, and biodiversity of culturable micro-organisms (analysis of 16S rRNA partial sequences) from four areas differing in salinity and Magnaporthe oryzae incidence in two moments of the crop cycle were studied. Results indicate that the dominant taxon in libraries from the four areas was Proteobacteria. Metabolic diversity was higher in areas affected only by salinity or incidence of Magnaporthe than in the control or area affected by both stresses. It seems that rice plants selected, in their rhizosphere, micro-organisms able to affect plant hormonal balance under all conditions, and this activity relied in different bacterial genera depending on the environmental stress. Conclusions: Bacterial genera for each stress, as well as generalist strains, were found present in all the studied areas. Potential molecular markers and taxonomic markers (Sphingobacteria for salt and Thermococci for Magnaporthe) of the different stress situations have been highlighted, and Class