Abstract
Bacterial inoculants are known to possess plant growth promoting abilities and have potential as liquid biofertilizer application. Four phytase producing bacterial isolates (phytase activity in the range of 0.076–0.174 U/mL), identified as Advenella species (PB-05, PB-06, and PB-10) and Cellulosimicrobium sp. PB-09, were analyzed for their plant growth promoting activities like siderophore production, IAA production, HCN production, ammonia production, phosphate solubilization, and antifungal activity. All isolates were positive for the above characteristics except for HCN production. The solubilization index for phosphorus on Pikovskaya agar plates was in the range of 2–4. Significant amount of IAA (7.19 to 35.03 μg/mL) production and solubilized phosphate (189.53 to 746.84 μg/mL) was noticed by these isolates at different time intervals. Besides that, a greenhouse study was also conducted with Indian mustard to evaluate the potential of these isolates to promote plant growth. Effect of seed bacterization on various plant growth parameters and P uptake by plant were used as indicators. The plant growth promoting ability of bacterial isolates in pot experiments was correlated to IAA production, phosphate solubilization, and other in vitro tests. On the basis of present findings, isolate PB-06 was most promising in plant growth promotion with multiple growth promoting characteristics.
Highlights
It is well known that a considerable number of bacterial species, mostly those associated with the plant rhizosphere, are able to exert a beneficial effect upon plant growth
Plant-stimulatory effects exerted by plant growth promoting bacteria (PGPB) might be due to an enhanced availability of limited plant nutrients such as nitrogen, phosphorus, B-vitamins, and amino acids in the rhizosphere caused by phosphate-solubilizing and diazotrophic bacteria [4, 5]
Based on 16S rDNA gene sequences, three isolates (PB-05, PB-06, PB-10) were identified as Advenella species (GenBank accession number JN630808.1, JN630809.1, and JQ727433.1 for PB-05, PB-06, and PB-10, resp.) while the fourth isolate was identified as Cellulosimicrobium sp
Summary
It is well known that a considerable number of bacterial species, mostly those associated with the plant rhizosphere, are able to exert a beneficial effect upon plant growth Their use as biofertilizers or control agents for agriculture improvement has been a focus of numerous researchers for a number of years. Organic P forms, phytates, are predominant in most soils (10–50% of total P) and must be mineralized by phytases (myo-inositol hexakisphosphate phosphohydrolases) to be available P for plants [8] In this context, bacteria with both activities, production of organic acids to solubilise inorganic P and production of phytase to mineralize phytate, have been isolated from rhizosphere [9, 10] and proposed as potential plant growth promoting rhizobacteria (PGPR) to be used in soil with high content of organic P. A similar study was conducted with mustard using Achromobacter sp., Bacillus sp., and Tetrathiobactor sp. [13]
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