A STUDY ON OPTIMIZATION OF PHOSPHATE SOLUBILIZING POTENTIAL OF BACTERIA AND THEIR EFFECT ON PLANT GROWTH WHEN APPLIED INDIVIDUALLY AND IN A CONSORTIUM

Abstract

The insoluble nature of a large portion of phosphorus present in soil restricts its uptake by plants. This often leads to
plant abnormalities associated with phosphate deficiency, in spite of its ample concentration in soil. Nature amends this
impediment with the help of phosphate solubilizing microorganisms that assist in making the phosphorus available to
plants. In the current study, eighteen potential phosphate solubilizing bacteria (PSB) were isolated from rhizosphere soil
of Maharashtra and Tamil Nadu (India). Among these isolates, P2 and P13 showed considerable solubilizing index of 2.35
and 3.06 corresponding to 16.47ppm and 17.88ppm phosphatesolubilization, respectively, in 48h. These isolates were
identified as Burkholderia cenocepacia (P2) and Enterobacter cloaceae (P13) by cultural, morphological, biochemical and 16S
rRNA sequence analysis. The optimum solubilization of phosphates was observed in NBRIP medium with 1% ammonium
sulphate, 0.4 O.D540nm, pH6-7 and temperature 28˚C -37˚C in 120h under shaker conditions by both isolates. Galactose
and sucrose were effective carbon sources forthe activity of E. cloaceae and B. cenocepacia niraar respectively. Under
optimized conditions, the consortium of PSB solubilized 59.52ppm phosphorus. The biofertilizer potential was also
observed on wheat (Triticum aestivum) and mustard (Brassica juncea) seeds by individual cultures as well as its consortia.
Significant enhancement of shoot length was observed on inoculation of test cultures in the soil. Further improvement
was observed on addition of tricalcium phosphate (TCP) along with test cultures. However, the highest growth
performance was observed in presence of the bacterial consortium and TCP.