Phosphate solubilizing bacteria isolated from the
rhizosphere soil and root cuttings of bush black pepper (Piper nigrum. L)
Soil Science, Indian Institute of Spices Research (Indian Council of Agricultural Research), P.B.No.1701, Marikunnu P.O, Calicut, Kerala, India, PIN-673012
#Present address
C/o Sajith.N.P, P.O. Box No.78313,
Nairobi, Kenya
Email: kavitharchand@hotmail.com
Bacterial isolates from the rhizosphere soil and root
cuttings of bush black pepper (Piper nigrum. L)(pepper raised by laterals) exhibiting high
phosphate solubilizing ability in-vitro is described in this paper. Microbial
phosphorus solubilization (MPS) trait was analyzed by determining the P
Solubilization Efficiency E (E = Diameter of bacterial growth/Diameter of
clearing zone x 100). The highest P solubilization efficiency was demonstrated
by the isolate PB-21 followed by the isolate PB-16, which was identified as Pseudomonas sp. All isolates under study released inorganic
phosphate from tricalcium phosphate (TCP) indicating the potential of these
strains to release soluble inorganic phosphates from fixed phosphate sources
for plant uptake. The isolate PIAR6-2 was able to solubilize 20.012% of P and
also fix atmospheric nitrogen, which was later identified as the nitrogen
fixing Azospirillum sp. Greenhouse trials using two systems; viz; Soil: Terracare (composted coir pith) and
Sand: Soil: FYM with three experimental sets such as rock phosphate (RP) as an
external P source, PSB isolate in combination with VAM and PSB isolate alone,
all against their respective control sets showed very clearly the growth
promoting activity of phosphate solubilizing bacteria. Field studies were also carried out
using these isolates and some promising results were obtained. Further studies
are required to analyze these strains to confirm its plant growth promoting
properties. The in-vitro
analyses and greenhouse studies of these bacteria reflect their potentiality as
efficient P solubilizer in black pepper growing soils.