Pseudomonas strains exhibiting high TCP solubilization
in vitro differed significantly in enhancing the plant growth in the soil indicating interplay of some other growth factors besides phosphate-solubilization (Tables 2, 6, and 7). Apart from making P available to the plants, phosphate-solubilizing microorganisms improve plant health directly by the production of phytohormones . Pseudomonas strains have been reported to vary in their ability for phytohormone production [32–34]. The bacterial strains also differ in utilizing root exudates in producing biologically active substances and root colonizing ability known to influence the plant growth-promoting action of rhizobacteria . Plant-microbe interaction is a complex phenomenon with the interplay of several mechanisms and environmental factors. The decrease in soil
pH in PSB treatments indicated the production of organic acids selleck chemical by Pseudomonas strains as also reported for phosphate-solubilizing Aspergillus niger and A. tubingensis . However, less pH decline in soil during plant growth promotion experiments than phosphate solubilization in culture medium could be due to the buffering selleck inhibitor nature of soil . The inorganic acids and H+ ions of microbial origin and H+ ions released from the plant roots during ammonium assimilation are also reported to influence the soil pH [22, 30, 37]. The Emricasan purchase studies have shown potential for plant growth promotion by P. trivialis BIHB 745, P. trivialis BIHB 747, Pseudomonas sp. BIHB 756 and P. poae BIHB
808 in the presence of TCP as the phosphate source. The native phosphate-solubilizing and stress-tolerant Pseudomonas strains are expected to cohabitate as effective microbial inoculants with the crops grown in the cold deserts of Lahaul and Spiti. Conclusion The present study revealed that the innate ability of organic acid production by Pseudomonas strains is independent of their genetic relatedness. Significant difference in plant growth promotion among the efficient phosphate-solubilizing Pseudomonas strains point at the need for selecting the potential strains based on plant growth promotion in the soils supplemented with insoluble phosphates for their targeted application. The PSB strains with high potential 3-oxoacyl-(acyl-carrier-protein) reductase for TCP solubilization appear promising for application in the Ca-rich and P-deficit soils in the cold deserts of Lahaul and Spiti for which field studies are required. Acknowledgements Authors acknowledge the Director, Institute of Himalayan Bioresource Technology for providing the necessary facilities. The Council of Scientific and Industrial Research, Govt. of India, is also acknowledged for the financial support under the CSIR Network Project “”Exploitation of India’s Rich Microbial Wealth”" (NWP 006). Thanks for the technical support are due to Mr. Ramdeen Prasad in chemical analyses and Mrs. Vijaylata Pathania for HPLC operation.