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The gradually dwindling reserves of rock phosphate, the primary material used in the manufacturing of phosphatic fertilizers, encourages researchers to look for ways to exploit the accumulated fixed P pool in soil. Phosphate solubilizing microorganisms (PSM) could be a viable option for addressing the problem at a lower cost. Keeping these in mind, the present study was undertaken to evaluate the changes in the distribution of P in soil as affected by P fertilization, phosphate solubilizing fungi (PSF) and liming vis-à-vis the contribution of these fractions toward P nutrition of a test crop soybean (Glycine max L.). A bulk surface soil sample (0–15 cm) was obtained from Negheriting tea estate of Golaghat district of Assam, India (Ultisol, pH = 4.23) and after processing, three levels of P [0, 50, and 100% of recommended dose of P (RDP)], two levels of lime [No lime, 1/10th of Lime Requirement (LR)] and two levels of PSF (No-PSF, PSF) were applied in a completely randomized design with three replications. Sequential P fractionation was done in the post-harvest soil. On an average, the abundance of different P fractions in the soil, expressed as % of total P, followed the order: residual P (67.5%)> Fe bound P (12.1%)> reductant soluble P (8.85%)> Al bound P (4.04%)> occluded P (3.79%)> Ca bound P (3.11%)> soluble and loosely bound P (0.46%). All the inorganic P fractions except the residual P, increased significantly with P fertilization. Either liming or PSF application significantly increased the soluble and loosely bound P fraction and decreased the Al bound and Fe bound P fractions in soil. Positive growth response of soybean was obtained due to the application of P, lime, and PSF. Liming increased the P uptake by 30.4% and dry matter yield of soybean by 18.5% over no liming. On the other hand, PSF inoculation increased the P uptake by 16.7% and dry matter yield by 7.77% over no inoculation. So, it is evident that in short term, either liming or PSF was able to solubilize the native soil P. Phosphorus×lime and lime×PSF interactions should also be exploited in future endeavors. [ABSTRACT FROM AUTHOR]

• Novel strategy using Meloidogyne incognita as bait could isolate parasitically potent rhizospheric Trichoderma spp. • First demonstration for nematophagous ability of T. inhamatum , T. kunmingense , T. lixii , T. neotropicale and T. yunnanense. • Elucidation of T. yunnanense as a potential and effective nematode biocontrol agent. Throughout the world Trichoderma spp. are majorly used as biocontrol agents for managing the economically important plant-parasitic nematodes. We employed a novel strategy to investigate the variety of rhizosphere dwelling Trichoderma species using the nematode Meloidogyne incognita as prey bait. Nine nematophagous Trichoderma spp., validated morphologically and molecularly, were discovered during the expedition in several agroclimatic zones of India. Molecular phylogenetic analysis of these species along with the reported Trichoderma spp. from 'Harzianum clade' from India indicated the true identity of Indian T. harzianum sensu stricto to be disputed. Nematophagous nature of the isolated species was confirmed through the presence of extracellular lytic enzymes, secondary metabolites, volatile organic compounds, Huperzine A, and tri -gene cluster variability. Besides, the most promising T. yunnanense isolate, shortlisted based on its in vitro potential against M. incognita , showed the highest levels of nematode parasitism, egg hatching inhibition and juvenile mortality compared to all other isolates and species. Expression of green fluorescent protein in T. yunnanense helped tracking its infection in the juveniles and further validated the nematode parasitizing capacity. The chosen isolate decreased the multiplication factor of M. incognita in pot culture assays and in organically produced capsicum in nematode-infected sick soil. It is interesting that the isolate also markedly increased the plant growth and yield, which was a bonus. Therefore, the performance of T. yunnanense demonstrated through various strategies instills high confidence to propose it as a prospective species for developing as commercially potent nematode biocontrol agent. [ABSTRACT FROM AUTHOR]