Organic acid production in vitro and plant growth promotion in maize under controlled environment by phosphate-solubilizing fluorescent Pseudomonas

Abstract

BackgroundPhosphorus deficiency is a major constraint to crop production due to rapid binding of the applied phosphorus into fixed forms not available to the plants. Microbial solubilization of inorganic phosphates has been attributed mainly to the production of organic acids. Phosphate-solubilizing microorganisms enhance plant growth under conditions of poor phosphorus availability by solubilizing insoluble phosphates in the soil. This paper describes the production of organic acids during inorganic phosphate solubilization and influence on plant growth as a function of phosphate solubilization by fluorescent Pseudomonas.ResultsNineteen phosphate-solubilizing fluorescent Pseudomonas strains of P. fluorescens, P. poae, P. trivialis, and Pseudomonas spp. produced gluconic acid, oxalic acid, 2-ketogluconic acid, lactic acid, succinic acid, formic acid, citric acid and malic acid in the culture filtrates during the solubilization of tricalcium phosphate, Mussoorie rock phosphate, Udaipur rock phosphate and North Carolina rock phosphate. The strains differed quantitatively and qualitatively in the production of organic acids during solubilization of phosphate substrates. Cluster analysis based on organic acid profiling revealed inter-species and intra-species variation in organic acids produced by Pseudomonas strains. The phosphate-solubilizing bacterial treatments P. trivialis BIHB 745, P. trivialis BIHB 747, Pseudomonas sp. BIHB 756 and P. poae BIHB 808 resulted in significantly higher or statistically at par growth and total N, P and K content over single super phosphate treatment in maize. These treatments also significantly affected pH, organic matter, and N, P, and K content of the soil.ConclusionThe results implied that organic acid production by Pseudomonas strains is independent of their genetic relatedness and each strain has its own ability of producing organic acids during the solubilization of inorganic phosphates. Significant difference in plant growth promotion by efficient phosphate-solubilizing Pseudomonas strains point at the need for selecting potential strains in plant growth promotion experiments in conjunction with various phosphate substrates for their targeted application as bioinoculants.

Phosphate solubilization and multiple plant growth promoting properties of rhizobacteria isolated from chickpea (Cicer aeritinum L.) producing areas of Ethiopia

“…These results are consistent with the report of earlier studies (Illmer and Schinner, 1995;Whitelaw, 2000;Naik et al, 2008;Vyas and Gulati, 2009) which showed that solubilization of insoluble phosphate sources were mediated specifically by the decreasing pH of the medium. It has been well documented that mineral phosphate solubilization by phosphate solubilizing bacteria strains results from the release of low molecular weight organic acids (Illmer and Schinner, 1995;Kim et al, 1997;Vyas and Gulati, 2009), probably as an interacting effect of their hydroxyl or carboxyl groups that may chelate the cations bound to the phosphate, thereby converting it into soluble forms (Kpomblekou and Tabatabi, 1994;Kim et al, 1997). Gram negative isolates displayed better performance in solubilization of different insoluble inorganic P sources compared to Gram positive phosphate solubilizing bacterial isolates in the study which is in line with the results of previous studies (Muleta et al, 2013;Tripura et al, 2007).…”

“…Several studies indicated that the drop in pH is due to the production of organic acids during bacterial growth (Chen et al, 2006;Muleta et al, 2013;Vyas and Gulati, 2009). The decreasing pH and the production of organic acids resulted in solubilization of a considerable amount of soluble P (Chen et al, 2006).…”

“…Phosphate solubilization that makes the P available in soil for plant growth is considered as one of the important attributes of PGPR (Chen et al, 2006), since phosphate solubilizing bacteria (PSB) are capable of converting insoluble phosphate to soluble orthophosphate ions which can be taken up and utilized by plants (Pal, 1998;Rodriguez and Fraga 1999;Chen et al, 2006;Vyas and Gulati, 2009). Previous studies already showed the presence of phosphate solubilizing bacteria (PSB) in the rhizosphere of different agriculturally important crops and their pivotal role in converting of insoluble P to the orthophosphate (Pal, 1998;Peix et al, 2001a;Rajapaksha and Senanayake, 2011).…”

Phosphate solubilizing bacteria: Assessment of their effect on growth promotion and phosphorous uptake of mung bean (Vigna radiata [L.] R. Wilczek)

“…A positive and significant correlation between phosphate solubilizing microorganisms and soil organic matter content was previously reported by Venkateswarlu et al (1984). Other researchers (Vyas and Gulati, 2009) also reported decreased soil pH in PSB-inoculated soil and indicated organic acid production of both strains. Soil pH reduction was found to be much lower than in the culture medium (Table 1), which could be due to the buffering nature of the soil used in the experiment (Gyaneshwar et al, 1998).…”

Citric Acid Production from Sugarcane Bagasse through Solid State Fermentation Method Using Aspergillus niger Mold and Optimization of Citric Acid Production by Taguchi Method

“…On the other hand, the high level of sugarcane bagasse production after the completion of Khuzestan province projects (three million tons per year) and the problems caused due to its storage require a comprehensive measurement in the direction of its optimized utilization and citric acid production (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16).…”