Isotope dilution analysis indicated that epi-GA 1 was an arte-The plant-growth-promoting rhizobacteria (PGPR), Bacillus pumilus and Bacillus licheniformis, isolated from the rhizo-fact. Likewise, iso-GA 3 is also probably an artifact spontaneously formed during extraction and/or analysis. In both sphere of alder (Alnus glutinosa [L.] Gaertn.) have a strong growth-promoting activity. Bioassay data showed that the culture media, GA 1 was present in higher concentrations (130-150 ng ml − 1 ) than GA 3 (50-60 ng ml − 1 ), GA 4 (8-12 dwarf phenotype induced in alder seedlings by paclobutrazol (an inhibitor of gibberellin [GA] biosynthesis) was effectively ng ml − 1 ) and GA 20 (2-3 ng ml − 1 ). The data indicated that culture of both bacteria accumulate bioactive C 19 -gibberellins reversed by applications of extracts from media incubated with both bacteria and also by exogenous GA 3 . Full-scan gas in relative high amounts and that these GAs appear to be physiologically active in the host plant. The evidence suggests chromatography-mass spectrometry analyses on extracts of these media showed the presence of GA 1 , GA 3 , GA 4 and that the promotion of stem elongation induced by the PGPR GA 20 , in addition to the isomers 3-epi-GA 1 and iso-GA 3 . could be mediated by bacterial GAs.

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The effect of co-inoculation with Pisolithus tinctorius and a PGPR belonging to the genus Bacillus (Bacillus licheniformis CECT 5106 and Bacillus pumilus CECT 5105) in enhancing growth of Pinus pinea plants and the changes that occurred in rhizosphere microbial communities and the degree of mycorrhization were evaluated. Both bacterial strains of Bacillus promote the growth of Pinus pinea seedlings, but this biological effect does not imply a synergic effect with mycorrhizal infection. However, the positive response to mycorrhiza in a longer-term experiment it could be expected. The introduction of both inocula causes an alteration in the microbial rhizosphere composition, despite the low levels of inocula that were found at the end of the assay.

The ability of six putative plant growth promoting rhizobacteria, isolated from the rhizosphere of Nicotiana glauca L., to stimulate growth and induce systemic resistance against Xanthomonas campestris CECT 95 in Arabidopsis thaliana L. Col-0 was evaluated. The six bacterial strains significantly reduced the disease symptoms caused by the pathogen compared to the controls, with the best results obtained with the Bacillus strain N11.37 and the Stenotrophomonas strain N6.8. These two strains were tested on A. thaliana NahG plants and jar1-1 and etr1-1 mutants, to elucidate whether the salicylic acid (SA)-dependent or SA-independent pathway was involved in the induction of systemic resistance. The results indicate that N6.8 induces the SA-dependent pathway. For N11.37 it is as yet not clear as in the etr1-1 mutants and NahG plants ISR is not expressed, while in jar1-1 it is. In addition, levels of SA were measured in Col-0 plants treated with N6.8 and N11.37 to confirm whether or not the two strains produced an increased level of SA. N6.8-and N11.37-induced plants showed higher levels of SA than the controls. It is concluded that N6.8 induces a SA-dependent pathway while N11.37 induces a pathway that is both ethylene (ET)-and SA-dependent.