The purpose of this research was to determine the efficacy of iron oxide nanoparticles (Fe₃O₄-NPs) using microalgal products as a plant growth stimulant and antifungal agent. The work was conducted with the phyco-synthesis and characterization of Fe₃O₄-NPs using 0.1 M ferric/ferrous chloride solution (2:1 ratio; 65 °C) with aqueous extract of the green microalga Chlorella K01. Protein, carbohydrate and polyphenol contents of Chlorella K01 extract were measured. The synthesized microalgal Fe₃O₄-NPs made a significant contribution to the germination and vigor index of rice, maize, mustard, green grams, and watermelons. Fe₃O₄-NPs also exhibited antifungal activity against Fusarium oxysporum, Fusarium tricinctum, Fusarium maniliforme, Rhizoctonia solani, and Phythium sp. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size analysers (PSA), and zeta potential (ZP) measurements were used to characterize these green fabricated magnetite NPs. FTIR analysis showed that the synergy of microalgal proteins, carbohydrtates and polyphenols is responsible for the biofabrication of iron nanoparticles. A spheroid dispersion of biosynthesized Fe₃O₄-NPs with an average diameter of 76.5 nm was produced in the synthetic process.

Modern agricultural management is heavily dependent on the fertilizers for promotion of crop production, but the massive use of inorganic and chemical-based fertilizers currently available may be a serious threat to human health and environment. Fertilizer research is therefore focusing on shifting to the exploitation of microbes as a more ecofriendly approach for sustainable agriculture. The biotechnological toolbox contains microorganisms such as microalgae, cyanobacteria, endo- and ecto-mycorrhizal fungi, rhizobacteria, and others that are able to live in association with higher plants. This review article focuses on the research achievements on microalgae- and cyanobacteria-based plant biofertilizers and biostimulants in the agricultural applications. The challenges to commercializing these kinds of biofertilizers are also discussed.

The scientific consensus is now on developing a biocontrol agent that can cause cellular metabolic reprogramming against agricultural pathogens. Biosynthesis of silver nanoparticles was performed by using phytopathogenic fungi (Alternaria sp.) isolated from banana cultivated soil. Alternaria sp. can grow very fast and produce high enough bioactive compounds. This study aims to biosynthesize silver nanoparticles (AgNPs) using fungal Alternaria sp.s metabolites as a safe antifungal agent against plant pathogenic fungi (Fusarium spp. and Alternaria sp.). To visualize the formation of AgNPs, analytical instruments were used, such as ultraviolet-visible (UV-Vis) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, scanning transmission electron microscopy (STEM), energy dispersive X-ray (EDX), and elemental mapping. The UV-visible spectra showed a peak at 435nm. Analysis of scanning transmission electron microscopy (STEM) micrographs evidenced that the size of synthesized silver nanoparticles ranged between 3 and 10nm. The resulting AgNPs showed distinct antifungal activity against selected plant pathogenic fungi. Synthesized AgNPs have demonstrated remarkable potential for the use of antifungal compounds to combat plant diseases.