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. 1. Introduction 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. Therefore, their use as biofertilizers or control agents for agriculture improvement has been a focus of numerous researchers for a number of years. Bacterial inoculants have been used to increase plant yields in several countries, and commercial products are currently available. For example, in India, several biofertilizers are commercially produced and employed with different crops, mostly using strains of Azotobacter, Rhizobium, Azospirillum, and Burkholderia. Several possible mechanisms have been proposed, including suppression of diseases caused by plant pathogens [1], competition with pathogenic microorganisms by colonizing roots [2], production of plant-growth-regulating substances such as indole-3-acetic acid (IAA) [3], and lowering ethylene levels in root cells. Plant-stimulatory effects exerted by plant growth promoting bacteria (PGPB) might also be due to an enhanced availability of limited plant nutrients such as nitrogen, phosphorus, B-vitamins, and amino acids in the
References
[1]
K. P. Smith, J. Handelsman, and R. M. Goodman, “Genetic basis in plants for interactions with disease-suppressive bacteria,” Proceedings of the National Academy of Sciences of the United States of America, vol. 96, no. 9, pp. 4786–4790, 1999.
[2]
L. C. Dekkers, C. C. Phoelich, L. Van Der Fits, and B. J. J. Lugtenberg, “A site-specific recombinase is required for competitive root colonization by Pseudomonas fluorescens WCS365,” Proceedings of the National Academy of Sciences of the United States of America, vol. 95, no. 12, pp. 7051–7056, 1998.
[3]
O. Steenhoudt and J. Vanderleyden, “Azospirillum, a free-living nitrogen-fixing bacterium closely associated with grasses: genetic, biochemical and ecological aspects,” FEMS Microbiology Reviews, vol. 24, no. 4, pp. 487–506, 2000.
[4]
C. S. Nautiyal, “An efficient microbiological growth medium for screening phosphate solubilizing microorganisms,” FEMS Microbiology Letters, vol. 170, no. 1, pp. 265–270, 1999.
[5]
H. Rózycki, H. Dahm, E. Strzelczyk, and C. Y. Li, “Diazotrophic bacteria in root-free soil and in the root zone of pine (Pinus sylvestris L.) and oak (Quercus robur L.),” Applied Soil Ecology, vol. 12, no. 3, pp. 239–250, 1999.
[6]
A. E. Richardson, P. A. Hadobas, and J. E. Hayes, “Extracellular secretion of Aspergillus phytase from Arabidopsis roots enables plants to obtain phosphorus from phytate,” Plant Journal, vol. 25, no. 6, pp. 641–649, 2001.
[7]
G. V. Bloemberg and B. J. J. Lugtenberg, “Molecular basis of plant growth promotion and biocontrol by rhizobacteria,” Current Opinion in Plant Biology, vol. 4, no. 4, pp. 343–350, 2001.
[8]
A. E. Richardson, P. A. Hadobas, J. E. Hayes, C. P. O'hara, and R. J. Simpson, “Utilization of phosphorus by pasture plants supplied with myo-inositol hexaphosphate is enhanced by the presence of soil micro-organisms,” Plant and Soil, vol. 229, no. 1, pp. 47–56, 2001.
[9]
M. A. Jorquera, M. T. Hernández, Z. Rengel, P. Marschner, and M. De La Luz Mora, “Isolation of culturable phosphobacteria with both phytate-mineralization and phosphate-solubilization activity from the rhizosphere of plants grown in a volcanic soil,” Biology and Fertility of Soils, vol. 44, no. 8, pp. 1025–1034, 2008.
[10]
M. A. Jorquera, D. E. Crowley, P. Marschner et al., “Identification of β-propeller phytase-encoding genes in culturable Paenibacillus and Bacillus spp. from the rhizosphere of pasture plants on volcanic soils,” FEMS Microbiology Ecology, vol. 75, no. 1, pp. 163–172, 2011.
[11]
O. A. Martínez, M. A. Jorquera, D. E. Crowley, and M. L. de la Mora, “Influence of nitrogen fertilisation on pasture culturable rhizobacteria occurrence and the role of environmental factors on their potential PGPR activities,” Biology and Fertility of Soils, vol. 47, no. 8, pp. 875–885, 2011.
[12]
B. Saharan and V. Nehra, “Plant growth promoting rhizobacteria: a critical review,” Life Science and Medicine Research, vol. 2011, pp. 1–17, 2011.
[13]
V. Kumar, P. Singh, M. A. Jorquera et al., “Isolation of phytase-producing bacteria from Himalayan soils and their effect on growth and phosphorus uptake of Indian mustard (Brassica juncea),” World Journal of Microbiology and Biotechnology, vol. 29, no. 8, pp. 1361–1369, 2013.
[14]
P. Kumar, Production and characterization of bacterial phytase and its assessment as feed additive [Ph.D. thesis], Department of Biochemistry, G. B. Pant University of Agriculture and Technology, Uttrakhand, India, 2010.
[15]
J. Kerovuo, M. Lauraeus, P. Nurminen, N. Kalkkinen, and J. Apajalahti, “Isolation, characterization, molecular gene cloning, and sequencing of a novel phytase from Bacillus subtilis,” Applied and Environmental Microbiology, vol. 64, no. 6, pp. 2079–2085, 1998.
[16]
A. J. Engelen, F. C. van der Heeft, P. H. Randsdorp, and E. L. Smit, “Simple and rapid determination of phytase activity,” Journal of AOAC International, vol. 77, no. 3, pp. 760–764, 1994.
[17]
R. I. Pikovskaya, “Mobilization of phosphorus in soil in connection with vital activity of some microbial species,” Microbiology, vol. 17, pp. 362–370, 1948.
[18]
M. Edi-Premono Moawad and P. L. G. Vleck, “Effect of phosphate solubilizing Pseudomonas putida on the growth of maize and its survival in the rhizosphere,” Indonesian Journal of Crop Science, vol. 11, pp. 13–23, 1996.
[19]
C. L. Patten and B. R. Glick, “Role of Pseudomonas putida indoleacetic acid in development of the host plant root system,” Applied and Environmental Microbiology, vol. 68, no. 8, pp. 3795–3801, 2002.
[20]
B. Schwyn and J. B. Neilands, “Universal chemical assay for the detection and determination of siderophores,” Analytical Biochemistry, vol. 160, no. 1, pp. 47–56, 1987.
[21]
A. W. Bakker and B. Schippers, “Microbial cyanide production in the rhizosphere in relation to potato yield reduction and Pseudomonas SPP-mediated plant growth-stimulation,” Soil Biology and Biochemistry, vol. 19, no. 4, pp. 451–457, 1987.
[22]
E. E. Idris, D. J. Iglesias, M. Talon, and R. Borriss, “Tryptophan-dependent production of Indole-3-Acetic Acid (IAA) affects level of plant growth promotion by Bacillus amyloliquefaciens FZB42,” Molecular Plant-Microbe Interactions, vol. 20, no. 6, pp. 619–626, 2007.
[23]
A. J. Engelen, F. C. Van Der Heeft, P. H. G. Randsdorp, W. A. C. Somers, J. Schaefer, and B. J. C. van der Vat, “Determination of phytase activity in feed by a colorimetric enzymatic method: collaborative interlaboratory study,” Journal of AOAC International, vol. 84, no. 3, pp. 629–633, 2001.
[24]
A. G. Murugesan and C. Rajakumari, “Environmental science and biotechnology theory and techniques,” Microbiology, vol. 144, pp. 1565–1573, 2006.
[25]
B. Neumann, A. Pospiech, and H. U. Schairer, “Rapid isolation of genomic DNA from gram-negative bacteria,” Trends in Genetics, vol. 8, no. 10, pp. 332–333, 1992.
[26]
R. Greiner and M. L. Alminger, “Stereospecificity of myo-inositol hexakisphosphate dephosphorylation by phytate-degrading enzymes of cereals,” Journal of Food Biochemistry, vol. 25, no. 3, pp. 229–248, 2001.
[27]
H. K. Gulati, B. S. Chadha, and H. S. Saini, “Production and characterization of thermostable alkaline phytase from Bacillus laevolacticus isolated from rhizosphere soil,” Journal of Industrial Microbiology and Biotechnology, vol. 34, no. 1, pp. 91–98, 2007.
[28]
R. Greiner, E. Haller, U. Konietzny, and K. Jany, “Purification and characterization of a phytase from Klebsiella terrigena,” Archives of Biochemistry and Biophysics, vol. 341, no. 2, pp. 201–206, 1997.
[29]
A. E. Richardson and P. A. Hadobas, “Soil isolates of Pseudomonas spp. that utilize inositol phosphates,” Canadian Journal of Microbiology, vol. 43, no. 6, pp. 509–516, 1997.
[30]
S. J. Yoon, Y. J. Choi, H. K. Min et al., “Isolation and identification of phytase-producing bacterium, Enterobacter sp. 4, and enzymatic properties of phytase enzyme,” Enzyme and Microbial Technology, vol. 18, no. 6, pp. 449–454, 1996.
[31]
E. E. Idriss, O. Makarewicz, A. Farouk et al., “Extracellular phytase activity of Bacillus amyloliquefaciens FZB45 contributes to its plant-growth-promoting effect,” Microbiology, vol. 148, no. 7, pp. 2097–2109, 2002.
[32]
H. A. Alikhani, N. Saleh-Rastin, and H. Antoun, “Phosphate solubilization activity of rhizobia native to Iranian soils,” Plant and Soil, vol. 287, no. 1-2, pp. 35–41, 2006.
[33]
P. Gyaneshwar, G. N. Kumar, L. J. Parekh, and P. S. Poole, “Role of soil microorganisms in improving P nutrition of plants,” Plant and Soil, vol. 245, no. 1, pp. 83–93, 2002.
[34]
A. J. Cattelan, P. G. Hartel, and J. J. Fuhrmann, “Screening for plant growth-promoting rhizobacteria to promote early soybean growth,” Soil Science Society of America Journal, vol. 63, no. 6, pp. 1670–1680, 1999.
[35]
A. Müller, H. Hillebrand, and E. W. Weiler, “Indole-3-acetic acid is synthesized from L-tryptophan in roots of Arabidopsis thaliana,” Planta, vol. 206, no. 3, pp. 362–369, 1998.
[36]
V. Leinhos and O. Vacek, “Biosynthesis of auxins by phosphate-solubilizing rhizobacteria from wheat (Triticum aestivum) and rye (Secale cereale),” Microbiological Research, vol. 149, no. 1, pp. 31–35, 1994.
[37]
A. R. Podile and G. K. Kishor, “Plant growth promoting rhizobacteria,” in Plant Associated Bacteria, S. S. Gnanamanickam, Ed., pp. 195–230, Springer, Dordrecht, The Netherlands, 2006.
