Aims: To study the diversity of the Pseudomonas populations isolated from t
hree different plant rhizospheres, namely pearl millet, cotton and paddy, g
rown in saline soils along the coastline of Southern India.
Methods and Results: The Pseudomonas populations were analysed for their bi
ochemical characters and genetic diversity using molecular tools including
RAPD and PCR-RFLP. The biochemical characterization, antibiotic resistance
assay and RAPD profiles revealed a largely homogenous population. Even in P
CR-RFLP restriction studies, only two groups of isolates were seen. One gro
up was predominant in all three rhizospheres, while the other minor group c
onsisted of salt-sensitive isolates restricted to the paddy rhizosphere alo
Conclusions: It was observed that increasing salinity caused a predominant
selection of salt-tolerant species, in particular Ps. pseudoalcaligenes and
Ps. alcaligenes irrespective of the host rhizosphere.
Significance and Impact of the Study: This study has reinstated the importa
nce of the soil over the host plant with regard to rhizosphere populations.
It has also resulted in the isolation of several salt-tolerant Pseudomonas
strains, which are being screened for their biological control activity ag
ainst common plant pathogens of the coastal agri-ecosystem.