Abstract

The present study investigates the strain Kosakonia sp. ICB117, an endophytic, N₂-fixing bacterium that belongs to a genus recently described. The bacteria were isolated from sugarcane stalks (Saccharum sp. variety SP791011) and inoculated into other sugarcane plants of the same variety. The effect of inoculation on sugarcane growth was then studied in the presence or absence of nitrate supplementation (10 mM). The following plant growth parameters were analyzed: biomass, plant height and number of leaves. Furthermore, CO₂ assimilation and the C and N content of plants were also determined, as was the size of the endophytic bacteria population resulting from the inoculation. The findings showed that inoculation with bacteria (both with or without additional nitrate) led to an increase of plant biomass, CO₂ assimilation, total C and N in the roots, and the number of leaves. In addition, the polyamine putrescine and indole-3-acetic acid were actively released by the bacterium in in vitro assays and might be released in internal plant tissues as well, resulting in plant growth promotion. In conclusion, inoculation of sugarcane with Kosakonia sp. ICB117 increased the efficiency of the plant’s metabolism.

Key words: Biological N, N-fixation, Saccharum sp., growth parameters, photosynthesis, nitrate supplementation, Brazil.