Abstract

HERBICIDE RESISTANCE AND PHOSPHATASE ENZYME ACTIVITY OF PHOSPHATE SOLUBILIZING BACTERIA IN RHIZOSPHERE SOIL

Murugan Karuppasamy*

Abstract

Phosphate solubilizing microbes plays an important role in plant nutrition through increase in phosphate uptake buy plants and used as biofertilizers of agricultural crops. Phosphate is one of the most vital macronutrient required for the growth and development of plants. A large number of microorganisms present in the rhizosphere are known to solubilizer and make available the insoluble phosphorus in the available form to the plants. Plant growth promoting rhizobacteria (PGPR) mediate the soil processes such as decomposition, nutrient mobilization, mineralization, solubilization, nitrogen fixation and growth hormone production. Rhizosphere soil of Oryza sativa (paddy plant) was collected from cultivated crop field and enumerated for total heterotrophic and phosphate solubilizing bacterial population. In this study, twenty five strains of phosphate solubilizing bacteria (PSB) were isolated by plate assay and characterized biochemically. Mineral phosphate solubilizing (MPS) activities of all isolates were tested on tricalcium phosphate of Pikovskaya‟s agar medium by analyzing the soluble phosphate content after 24 hours of incubation at 370C. The aim of the present study was to screen the phosphatase enzymes of phosphate solubilizing bacteria and to access their potential tolerance to herbicides (one shot). The heterotrophic bacterial load was found in the order of 10 CFU/gm and the phosphate solubilizer of 10 CFU/gm. The phosphate solubilizing bacteria was composed of Bacillus sp. and Micrococcus sp. with a lone of Pseudomonas sp. Both Bacillus sp. and Micrococcus sp. were noted to produce phosphatase at neutral pH and at 450C with the exception of Bacillus sp. phosphate solubilizer (PS) 25. Probably this bacterium is secreting alkaline phosphatase that has temperature optima at 35°C. None of the three representative bacterial strains were found to tolerate the most commonly used herbicide (one shot) at the concentration of 20 ppm. Only Pseudomonas sp. was recorded to tolerate this herbicide at 10 ppm. Further understandings on the nature of the enzyme, optimization on its activity would provide basic data for the commercial production of these enzymes.

Keywords: Rhizosphere soil, Pikovskaya's agar medium, Griseofulvin, Phosphatase enzyme, Phenolphthalein diphosphate and Herbicide.