The fungus Fusarium oxysporum Schlecht f. sp. radicis-lycopersici Jarvis and Shoemaker (FORL) causes crown and root rot in tomato (Lycopersicon esculentum Mill.), which is a serious problem for field and greenhouse production causing significant losses. The main objective of this study was to test the efficacy of two commercial bacteria strains Pseudomonas sp. ”Proradix” (DSMZ 13134) (Proradix®, Sourcon Padena, Tübingen-Germany) and Bacillus amyloliquefaciens FZB42 (RhizoVital® 42 TB, ABiTEP, Berlin, Germany) in improving mycorrhization, nutrient status and plant growth of tomato affected by FORL. Soil inoculation with P. sp. ”Proradix” and B. amyloliquefaciens FZB42 in single and combined application significantly improved root and shoot biomass production of tomato, and P, Mn and Zn shoot concentrations in pathogen-infested soil. After application of the bacteria strains, roots of tomato were healthier and showed a significantly higher colonization by arbuscular mycorrhizal fungi if the latter was inoculated too. Combined inoculationd with the bacteria strains and arbuscular mycorrhizal fungi increased the observed effects on dry matter and shoot nutrient concentrations. However, clear synergistic effects could not be detected. The results obtained suggest an important role of rhizosphere interactions for the expression of bio-control mechanisms by inoculation with effective Pseudomonas and Bacillus strains in addition to simple antagonistic effects.

An investigation was carried out on the effects of two plant growth-promoting rhizobacteria and Rhizobium on the seedling growth of Paraseriathes falcataria (l.) Nielsen and mycorrhizal development in two soils with contrasting level of pH (5 and 6) in a greenhouse. The results show that inoculation of Paraserianthes seeds with Pseudomonas sp ‘‘Proradix’’ (DSMZ 13134) and Bacillus amyloliquefaciens FZB42 in single or combined application significantly increased root and shoot dry weight, mycorrhizal root colonization, and nutrient concentration (P. Zn and Cu) in the shoots of Paraseriathes seedlings compared to untreated control. Only in the soil with pH 5, an inoculation with P. sp. ”Proradix®“ in addition to Rhizobium inoculation led to a further increase of all measured variables compared to Rhizobium inoculation alone. In all other treatments, inoculation with PGPRs in addition to Rhizobium inoculation did not lead to a significant increase of any of the measured variables. The results demonstrate that plant growth-promoting rhizobacteria have the potential to promote the indigenous arbuscular mycorrhizal fungi establishment and the growth of Paraseriathes seedlings