A novel method of management of maize pathogens in vitro and in vivo using newly synthesized copper nanoparticles (CuNPs) has been documented in this study. CuNPs have been synthesized using CuSO4 as a precursor, NaBH4 and ascorbic acid as a reducing agent, and polyethylene glycol 8000 (PEG-8000) as a stabilizing agent. Characterization of CuNPs using a Transmission Electron Microscope (TEM) confirmed the nanoparticles' size range of 35–70 nm. Fourier transform infrared spectroscopy (FTIR) revealed the association of alcohol groups and allyl halides group with CuNPs. The synthesized CuNPs exhibited significant inhibition at 20 ppm of three pathogenic fungi namely Macrophomina phaseolina, Bipolaris maydis, and Fusarium verticillioides, and at 50 ppm against Rhizoctonia solani. Bactericidal property of CuNPs was evidenced against Erwinia carotovora and Ralstonia solanacearum at 30 ppm. Evaluation of CuNPs in vivo against two diseases viz., maydis leaf blight (MLB) and banded leaf and sheath blight (BLSB) culminated in a reduction in percent disease index (PDI). Seed treatment together with foliar spray @ 300 ppm of CuNPs resulted in a significant reduction of MLB. However, BLSB disease was reduced relatively less at the same aforesaid concentration nevertheless; it was evinced best in controlling BLSB disease. CuNPs were found inimical against beneficial fungi and bacteria. However, a positive effect was observed on soil enzyme activities namely dehydrogenase, urease, and alkaline phosphatase and maize seedling characters viz., shoot length, root length, number of roots per seedlings, fresh and dry weight.

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.

Demand for food, fibre and medicines has been boosted tremendously for the explosive population, which has certainly built pressure on the agriculture-based sector to meet the requirements by various means. Nano-fungicides are fungicidal formulation that contains fungicide particle size 10−9. These nano-fungicides contain antimicrobial properties, which could be utilized against plant pathogens such as fungi and bacteria as a potent pesticide. Nanoparticles of fungicidal properties can be synthesized using different metals via. copper, silver, etc. Recent reports suggest that nanoparticles can also be synthesized using biological means such as fungi which pose effective fungicidal actions. Nanopesticides have their application in various areas such as agriculture, food, medical industries, storage packaging of food, etc. The present chapter will light upon the types and methods of nanoparticle synthesis and their applications. Categories of nano pesticides based on their nature application and source of synthesis will also be covered. Inventions in nano pesticides could lead us to less dependence upon conventional chemical pesticides which have adverse effects on climate, animal and human health.

Nanoscience has opened new vistas to manage phytopathogens, improve crop productivity by the development of new varieties, and control infectious diseases in humans. Silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) are highly acclaimed for their wide potential application in various fields. Chemical and physical methods of synthesis of AgNPs and AuNPs are widely used; however, such methods possess numerous setbacks, such as the production of toxic residues and indispensable need for high energy. Biosynthesis of nanoparticles is a cost-effective and environmentally friendly method. A plethora of species of plant, bacteria, fungi, etc. is available with potential biosynthesis ability. Fungi are a highly preferred organism owing to the ability to secrete a large number of extracellular enzymes, metal toxicity tolerance and bioaccumulation ability, and ease of handling of its biomass. Extracellular enzymes act both as reducing as well as capping agents. Two different methods are used by fungi for synthesis viz., intercellular and extracellular synthesis. Extracellular synthesis is preferred over intercellular as it bypasses several down streaming processes. During the reduction process, the metal ions (Ag2+ and Au3+) are converted to an elemental state (Ag0 and Au0 ) which is in the nano range. Due to their large surface-to-volume ratio and other properties, they become very effective against other pathogens. There is an excellent prospect of the use of nanoparticles in the field of agriculture and health and nanoparticles synthesized using a biological method involving fungi could be a boon.

No abstract