UTILIZATION OF ROOT NODULATING BACTERIA (RNB) AS POTENTIAL PLANT GROWTH PROMOTING RHIZOBACTERIA (PGPR) FOR NON-LEGUMINOUS CROPS
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Date
2009-09-09
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University of Agricultural Sciences GKVK, Bangalore
Abstract
The beneficial effect of Rhizobium and Bradyrhizobium on legumes in terms of nitrogen fixation are well known. However, recent reports indicate that these symbiotic bacteria may have a potential to perform as PGPR with non-legumes. Four root nodulating bacteria were isolated from cowpea, pigeonpea, chickpea and soybean which were short rods and gram negative. All four isolates showed positive for the Rhizobium in plant infection test. Bradyrhizobium japonicum and Bradyrhizobium sp (c) produced maximum water and alkali stable polysaccharides. Bradyrhizobium japonicum and Bradyrhizobium sp (c) solubilized phosphorous in both Sperber’s and Pikovskaya’s medium. Bradyrhizobium japonicum and Bradyrhizobium sp (c) produced HCN on YEMA with picric acid and none of the cultures produced siderophores on CAS agar. Bradyrhizobium japonicum and Bradyrhizobium sp (c) produced maximum amounts of IAA, Zeatin and GA. Only Mesorhizobium (Cicer) produced ABA. Greenhouse experiments revealed that maximum biomass, root and shoot P and more of chlorophyll content were observed in seeds inoculated with Bradyrhizobium strains which was statistically on par to inoculation effects of Pseudomonas fluorescens. Among three carrier materials used liquid formulations performed better than lignite and broth. The presence of nutrients shown superior results than the absence of nutrients. Field experiments revealed that inoculation of Bradyrhizobium strains also produced the same effect as inoculation of standard PGPR Pseudomonas fluorescens in terms of shoot N and P concentrations and grain yield in ragi and sunflower and fruit yield in tomato. The results of these studies indicated that Bradyrhizobium strains may be used as PGPR for growth and enhanced production of non-legumes. Statistically, results obtained from rhizobial inoculation were on par with standard PGPR i. e Pseudomonas fluorescens. Among the inoculant formulations liquid formulation, was better than lignite and broth.
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