Die Bodenkultur - Journal for Land Management, Food and Environment

M.M. Joe and P.K. Sivakumaar:

Role of certain cationic compounds on the enhancement of flocculation in Azospirillum brasilense MTCC-125:

Bioinoculation effect on growth of sunflower


The phenomenon of flocculation or aggregation in Azospirillum brasilense MTCC-125 was enhanced by the addition of certain cationic compounds. Among different cationic compounds studied, addition of aluminum sulphate favoured the highest aggregation percentage (80.00), and a floc yield of 1.26 gL-1 dry wt. These flocculated cells, when compared with control exhibited high levels of EPS and PHB content, while the protein content was found to be low. Flocculated cells when subjected to stress tolerance experiments exhibited a high degree of osmotic, thermal, and desiccation resistance. The survivability of these flocculated cells in different inoculant carrier material was also found to be higher, when compared with control. The treatment effect of these flocculated cells was studied for vital seedling parameters such as vigour index and germination percentage in sunflower crop followed by a pot culture study to compare the efficiency of these flocculated cells with normal cells for its phyto-stimulatory effect. It has been found that seed treatment with these flocculated cells exhibited a higher germination percentage and vigour index and a positive trend on the enhancement of certain growth parameters in sunflower crop. Key words:  Azospirillum brasilense Sp-7, aggregation, flocculation, poly-β-hydroxybutyrate (PHB), exocellular polysaccharides (EPS), tolerance, carrier material, sunflower.