Sustainable food production is necessary to meet the demand of the incessantly growing human population. Phytopathogens pose a major constraint in food production, and the use of conventional fungicides to manage them is under the purview of criticism due to their numerous setbacks. In the present study, essential oil-grafted copper nanoparticles (EGC) were generated, characterized, and evaluated against the maize fungal pathogens, viz., Bipolaris maydis, Rhizoctonia solani f. sp. sasakii, Macrophomina phaseolina, Fusarium verticillioides, and Sclerotium rolfsii. The ED₅₀ for the fungi under study ranged from 43 to 56 μg ml⁻¹, and a significant inhibition was observed at a low dose of 20 μg ml⁻¹ under in vitro conditions. Under net house conditions, seed treatment + foliar spray at 250 and 500 mg L⁻¹ of EGC performed remarkably against maydis leaf blight (MLB), with reduced percent disease index (PDI) by 27.116 and 25.292%, respectively, in two Kharif seasons (May-Sep, 2021, 2022). The activity of enzymatic antioxidants, viz., β-1, 3-glucanase, PAL, POX, and PPO, and a non-enzymatic antioxidant (total phenolics) was increased in treated maize plants, indicating host defense was triggered. The optimum concentrations of EGC (250 mg L⁻¹ and 500 mg L⁻¹) exhibited improved physiological characteristics such as photosynthetic activity, shoot biomass, plant height, germination percentage, vigor index, and root system traits. However, higher concentrations of 1,000 mg L⁻¹ rendered phytotoxicity, reducing growth, biomass, and copper bioaccumulation to high toxic levels, mainly in the foliar-sprayed maize leaves. In addition, EGC and copper nanoparticles (CuNPs) at 1,000 mg L⁻¹ reduced the absorption and concentration of manganese and zinc indicating a negative correlation between Cu and Mn/Zn. Our study proposes that the CuNPs combined with EO (Clove oil) exhibit astounding synergistic efficacy against maize fungal pathogens and optimized concentrations can be used as an alternative to commercial fungicides without any serious impact on environmental health.

Plant growth-promoting endophytic microbes have drawn the attention of researchers owing to their ability to confer fitness benefits in many plant species. Here, we report agriculturally beneficial traits of rice-leaf-adapted endophytic Microbacterium testaceum. Our polyphasic taxonomic investigations revealed its identity as M. testaceum. The bacterium displayed typical endophytism in rice leaves, indicated by the green fluorescence of GFP-tagged M. testaceum in confocal laser scanning microscopy. Furthermore, the bacterium showed mineral solubilization and production of IAA, ammonia, and hydrolytic enzymes. Tobacco leaf infiltration assay confirmed its non-pathogenic nature on plants. The bacterium showed antifungal activity on Magnaporthe oryzae, as exemplified by secreted and volatile organic metabolome-mediated mycelial growth inhibition. GC-MS analysis of the volatilome of M. testaceum indicated the abundance of antimicrobial compounds. Bacterization of rice seedlings showed phenotypic traits of MAMP-triggered immunity (MTI), over-expression of OsNPR1 and OsCERK, and the consequent blast suppressive activity. Strikingly, M. testaceum induced the transcriptional tradeoff between physiological growth and host defense pathways as indicated by up- and downregulated DEGs. Coupled with its plant probiotic features and the defense elicitation activity, the present study paves the way for developing Microbacterium testaceum-mediated bioformulation for sustainably managing rice blast disease.

Since time immemorial organic amendments have been an important strategy for improving soil fertility and suppressing a wide range of soil-borne pathogens. Biochar, a charcoal-like amendment has true potential in managing phytopathogens with an eco-friendly approach. It is produced by subjecting plant materials and agricultural waste to high temperatures of around 900°C in limited oxygen conditions. Biochar is considered to be an excellent carbon sequester and has an undeniably imperative role in improving soil properties. Biochar has innumerable applications in the remediation of environmental pollutants by immobilizing heavy metals such as Cadmium and Arsenic and degradation of dyes and pesticides. One of the most significant advantages of biochar in addition to mitigating environmental pollution is effectively managing plant pathogens by altering soil physical and chemical properties and promoting antagonistic microorganisms. Biochar directly suppresses plant pathogens by priming plant defense mechanisms. For instance, sugarcane bagasse biochar remediates Cd from contaminated soil, and citrus wood biochar induces systemic resistance against Botrytis cinerea in host-Lycopersicon esculentum, Capsicum annuum L. cv. Maccabi and Fragaria ananassa. Nevertheless, it is essential to acknowledge its limitations, such as the potential to absorb and enhance the residual activity of harmful chemicals. Further research is needed to develop a deeper understanding of biochar’s properties and mechanisms for more effective results. Advanced techniques like meta-transcriptomics and metaproteomics hold the potential to provide invaluable insights into this field. The review provides a comprehensive overview of current information regarding biochar, covering its production techniques and highlighting its agricultural benefits, with a particular focus on its role in plant disease management. Furthermore, the associated risks and concerns are also discussed.