Nitrogen Fixation and Indole Acetic Acid Production Potential of Bacteria Isolated from Rhizosphere of Sugarcane (Saccharum officinarum L.)

Twelve bacterial strains were isolated from root and rhizosphere samples collected from different sugarcane growing areas. Of these strains, ten strains were identified as Pseudomonas and two as Azotobacter on the basis of colonyand cell-morphology. Among isolates the presence of nifH gene was detected only in two Azotobacter strains (Azoto1 and Azoto2). Acetylene reduction activity of the strains Azoto1 and Azoto2 determined in N-free medium was 1966 and 4210 nmole C H /vial/24h, respectively. All isolates showed IAA 2 4 production in growth medium containing tryptophane as a precursor. Maximum IAA production (4.49mg/L) was detected in isolate A17 where as IAA production in strains A4 and A11 was also significant. Values for IAA production by nitrogen fixing isolates Azoto1 and Azoto2 were comparatively low (0.2 and 0.1mg/L respectively). For rapid screening of bacterial isolates from sugarcane, heterologous plant host (sorghum) was used as a test plant. Most of the strains showed beneficial effects on root length, root area and plant dry weight which were comparable to those observed in treatments where confirmed PGPR were used as positive control. Beneficial effects of inoculation on sugarcane grown in pots were also observed.