Survival of Azospirillum brasilense flocculated cells in alginate and its inoculation effect on growth and yield of maize under water deficit conditions

Abstract The objective of this study was to compare the efficiency of Azospirillum brasilense MTCC125 flocculated cells with standard grown cells under in vitro conditions and in association with maize ( Zea mays L.) under field conditions. The results revealed that A. brasilense flocculated cells had higher survivability in alginate bead (37 × 10 6  CFU g −1 dry wt.) and disinfected soil (11 × 10 6  CFU g −1 dry wt.) after 12 months of storage in room temperature. A. brasilense flocculated cells offered a higher degree of resistance to dehydration in terms of reduction in water availability ( a w ) and their survivability was 12% higher in soil and 27% higher in alginate compared to standard grown cells. The adhesion efficiency of A. brasilense flocculated cells was 54% higher to hydrophobic polystyrene and 101% higher to maize roots when compared to standard grown A. brasilense cells. Furthermore, flocculated cells had better spermoplane survivability (48%) and spermosphere colonization (73%) along with a concomitant enhancement on the germination percentage (11%) and vigor index (23%) of maize. Field studies with A. brasilense flocculated cells conducted under normal irrigated conditions and by withholding irrigation at 25, 50, and 75% available water-holding capacity (AWHC) showed a significant increase in plant height (19%), plant dry weight (16%), grain yield (31%), stover yield (17%) and nitrogen uptake (18%) compared with standard grown cell treatment.