Interaction of plant growth promoting microorganisms (PGPMs) with plants involves interplay at physical, physiological and molecular levels. Proliferation and root colonization of PGPMs manipulate the rhizosphere to optimize plant functions. This benefits plant by nutrient enrichment and induction of plant vigor and defense system. The present work aims to decipher the rhizosphere modulations promoted under different fertilization regimes by an organic acid producing Trichoderma koningiopsis strain (NBRI-PR5). Chickpea was selected as the host plant for the study since it responds well to the application of in/organic fertilizers and PGPMs. Microbial communities associated with the rhizosphere were studied by determining culturable population of heterogeneous microflora, and rhizosphere functions were studied by determining the soil enzyme activities and HPLC profiles of organic acids in root exudates. Application of NBRI-PR5 induced changes in rhizosphere in consent with the amendments. The changes observed in microbial populations were found to be associated with the rhizosphere enzymes. The inhibitory effect of chemical fertilizers on rhizosphere microflora was evident from least bacterial CFU observed in the NPK treatments. No detection of alkaline phosphatase enzyme in all the treatments with NBRI-PR5, with organic or inorganic amendments evidently represents the acidified rhizosphere. Similarly, an opposite trend in DHA and protease enzyme activities in the rhizosphere of FYM and FYM+PR5 treated plants showed that NBRI-PR5 had reframed microbial activities to facilitate nutrient uptake in plants rather than fix in the microbes. It is concluded from the study that NBRI-PR5 fatefully modulates rhizosphere activities, specific to different fertilization regimes by varying the enzyme activities to maximize the utilization of available nutrients.
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