Interaction Between a Va Mycorrhiza and Azotobacter and Their Effects on Rhizosphere Microflora and Plant Growth

SUMMARY Larger populations of bacteria and actinomycetes were recovered from the rhizospheres of tomato plants inoculated with the mycorrhizal fungus Glomus fasciculatus and Azotobacter chroococcum , either individually or together, than from those of non‐inoculated plants. Plants inoculated with both Glomus fasciculatus and Azotobacter chroococcum had greater numbers of bacteria and actinomycetes in the rhizosphere than plants inoculated with either Glomus fasciculatus or Azotobacter chroococcum alone. The fungal population of the rhizosphere was unaffected by inoculation with Glomus fasciculatus but reduced by inoculation with Azotobacter chroococcum. Inoculation of tomato with Glomus fasciculatus increased the Azotobacter chroococcum population in the rhizosphere which was maintained at a high level for a longer time. Inoculation of tomato roots with A. chroococcum enhanced infection and spore production by Glomus fasciculatus. The dry weights of tomato plants inoculated with both G. fasciculatus and Azotobacter chroococcum were significantly (62%) greater than non‐inoculated plants. These results suggest a synergistic or additive interaction between Glomus fasciculatus and Azotobacter chroococcum.