Diversity of pseudomonads isolated from three different plant rhizospheres

Abstract

Aims: To study the diversity of the Pseudomonas populations isolated from three different plant rhizospheres, namely pearl millet, cotton and paddy, grown in saline soils along the coastline of Southern India. Methods and Results: The Pseudomonas populations were analysed for their biochemical characters and genetic diversity using molecular tools including RAPD and PCR-RFLP. The biochemical characterization, antibiotic resistance assay and RAPD pro®les revealed a largely homogenous population. Even in PCR-RFLP restriction studies, only two groups of isolates were seen. One group was predominant in all three rhizospheres, while the other minor group consisted of salt-sensitive isolates restricted to the paddy rhizosphere alone. Conclusions: It was observed that increasing salinity caused a predominant selection of salttolerant species, in particular Ps. pseudoalcaligenes and Ps. alcaligenes, irrespective of the host rhizosphere. Signi®cance and Impact of the Study: This study has reinstated the importance 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 against common plant pathogens of the coastal agri-ecosystem.

Biodiversity of phosphate solubilizing bacteria in rhizosphere of chickpea, mustard and wheat grown in different regions of Haryana

“…The results show that the IAR of different isolates is not confi ned to any particular crop or region of Haryana. Diversity in soil bacteria using IAR pattern has been demonstrated in earlier studies [31,32] also.…”

Nature and role of root exudates: Efficacy in bioremediation

“…Beside these abiotic factors, few others such as moisture, humidity, wind speed and light intensity, elevated CO 2 pesticides, available space, atmosphereic nitrogen deposition, ozone, physical disturbance, fire, irrigation, erosion, altitude and latitude are also influencing the exudation (Torsivik et al, 1996). Some soil abiotic factors resembling compaction, soil type, salinity, soil pH, metal toxicity, water availability, organic matter, cation and anion exchange, drainage, aeration, rooting depth, soil texture, soil structure and redox-potential influence the release of organic chemical from plant root (Ross et al, 2000;Rangarajan et al, 2001). …”

Molecular characterization and Antagonistic Potential of phenazine-1-carboxylic acid producing Pseudomonas fluorescens isolates from economically important crops in South India

“…Pseudomonas fluorescens is a plant growth promoting rhizobacteria which stimulate growth to the plant bacteria is mainly because of the production of indole-3-acetic acid (IAA) [1,2] and it has a capability to suppress soil borne pathogens in various crops [3] with respect to production of secondary metabolites such as Hydrogen cyanide (HCN), Phytohormones, Siderophores, Antibiotics like 2,4-Diacetylphloroglucinol, Phenazine-1-Carboxylic Acid, Pyocyanin, Pyrrolnitrin, Pyoluteorin [4,5,6,7,8]. P. fluorescens also produce antifungal metabolites which suppresses the soil borne fungal pathogens [9,10,11].…”