Background Biocontrol is an effective strategy in the integrated management of plant diseases, now more as a necessity than choice, in the present era of environmental and health awareness. Microbial diversity is a wonder by nature that inspires to explore and accordingly, the diversity analysis of the isolated microbes revealed their morphological and molecular differences. The DNA provides a common platform to store the microbial information in the form of databases in public domain that can be used by anyone from anywhere. Results Exploration for native microbes in the present study resulted in isolation of different isolates of Trichoderma and Bacillus. The microbes were identified using morphological traits and molecular markers and the key conserved 18S and 16S gene sequences submitted with the appropriate repositories. Nucleotide analysis indicated a close phylogenetic relationship between BIK 2 and BIK 3 (Bacillus isolates) and within all the 5 Trichoderma isolates. The percent disease reduction of Rhizoctonia solani and Xanthomonas oryzae pv. oryzae (Xoo) was more in plants treated with consortia of the Trichoderma (61.13%) and Bacillus (53.59%) isolates, respectively. Screening of plant growth promotion activities, percentage increase in root (41.00%) and shoot length (44.77%) were found to be maximum in Trichoderma consortia treated plants. Conclusions Three Bacillus and one Trichoderma strains, viz., B. velezensis, B. subtilis and B. paralicheniformis and Trichoderma asperellum, were identified and found to be effective against R. solani and Xoo pathogens of rice. In vitro and in vivo studies indicated that TAIK1 and BIK3 were found to be the most potential isolates among others isolated. Ability to improve plant growth was more pronounced by consortia of microbes.

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Rhizosphere essentially harbours native bioagents that are beneficial to plants growth and development, stress tolerance and competitive advantage over its rivals. The bioagents often exhibits multiple mechanisms including secretion of secondary metabolites, phytohormones and defense enzymes to offer such advantages to the host plants. Stem rot and false smut caused by Sclerotium hydrophilumand Ustilaginoidea virensrespectively, are two major constraints in India and other countries where rice is cultivated. There are reports on the critical role of microbial phytohormones viz., ABA and SA, IAA, GA, zeatin on growth and stress of plants. They play a role in the regulation of plant immune responses by eliciting induced systemic resistance (ISR) in host plants against invading pathogens. Accordingly, we studied the activity of native bioagents viz., Trichoderma asperellum strain TAIK 1, Bacillus cabrialesii strain BIK3, Pseudomonas putida strain PIK1 and Pseudomonas otitidis strain POPS1 on enhancement of plant growth, increase in defence enzymes and reduction in severity of stem rot and false smut diseases of rice. We followed the Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometric (LC-ESI-MS/MS) method for the analysis of the phytohormones viz., IAA, GA, Zeatin, SA and ABA released by the bioagents. Bioagents treated plants showed 100% germination, enhanced plant growth parameters and reduction in percent disease index like 20.98% (stem rot), 23.14% (false smut) over the control plants (70.01% for stem rot and 75.24% for false smut). Our study indicated a direct relationship between the number and intensity of phytohormones released by the bioagents and the plant growth and disease suppression in rice.

Soil is a crucial component for plant growth, as it provides water, nutrients, and mechanical support. Various factors, such as crop cultivation, microflora, nutrient addition, and water availability, significantly affect soil properties. Maintaining soil health is important, and one approach is the introduction of native organisms with multifaceted activities. In this study, the effects of four native microbes (Trichoderma asperellum strain TAIK 1, Bacillus cabrialesii strain BIK3, Pseudomonas putida strain PIK1, and Pseudomonas otitidis strain POPS1) and their consortia on soil health, plant growth, and the incidence of stem rot disease caused by Sclerotium oryzae in rice are evaluated. Upon bioagent treatment of soil through seed treatment or soil application, variations in chemical properties of the soil were observed, viz., pH, Electrical Conductivity (EC), Organic Carbon (OC), available Soil Nitrogen (SN), Soil Phosphorus (SP), Soil Potassium (SK), and soil enzymes (urease, acid and alkaline phosphatase, dehydrogenase), compared to untreated soils. The treated seeds with the consortia of four native bioagents resulted in a significant increase in plant height (39.16%), number of panicles (30.29%), and average grain yield (41.36%) over control plants. Under controlled conditions, the bioagents-treated plants showed a 69.37% reduction in stem rot disease. The findings of this study indicate a positive correlation between soil properties and plant growth as well as a highly negative association with stem rot disease severity. The results suggest that using native bioagents as a management strategy can control stem rot disease and enhance crop productivity while reducing reliance on chemical interventions. These findings provide valuable insights for the development of sustainable agricultural practices that promote soil health, plant growth, and disease management.

Bg_9562 is a potential broad-spectrum antifungal effector protein derived from the bacteria Burkholderia gladioli strain NGJ1 and is effective against Rhizoctonia solani, the causal agent of sheath blight in rice. In the present study, in vitro antifungal assays showed that Bg_9562 was efficient at 35 °C and 45 °C and ineffective either at high acidic pH (3.0) or alkaline pH (9.5) conditions. Compatibility studies between the native bioagents Trichoderma asperellum TAIK1 and Bacillus subtilis BIK3 indicated that Bg_9562 was compatible with the bioagents. A field study using foliar spray of the Bg_9562 protein indicated the need of formulating the protein before its application. In silico analysis predicted that Bg_9562 possess 111 amino acid residues (46 hydrophobic residues, 12 positive and 8 negative residues) with the high aliphatic index of 89.92, attributing to its thermostability with a half-life of 30 h. Bg_9562 (C491H813N137O166S5) possessed a protein binding potential of 1.27 kcal/mol with a better possibility of interacting and perturbing the membrane, the main target for antimicrobial proteins. The secondary structure revealed the predominance of random coils in its structure, and the best 3D model of Bg_9562 was predicted using an ab initio method with Robetta and AlphaFold 2. The predicted binding ligands were nucleic acids and zinc with confidence scores of 0.07 and 0.05, respectively. The N-terminal region (1–14 residues) and C-terminal region (101 to 111) of Bg_9562 residues were predicted to be disordered regions. Stability and binding properties of the protein from the above studies would help to encapsulate Bg_9562 using a suitable carrier to maintain efficiency and improve delivery against Rhizoctonia solani in the most challenging rice ecosphere.