ABSTRACT
Synthesizing nanoparticles through a green synthesis approach is common nowadays. Cyanobacteria have attained great importance in the field of biosynthesis of nanoparticles as there is no use of toxic chemicals as reducing or capping agents for the synthesis of metal oxide nanoparticles. Micronutrient-based nano-formulations have become a topic of great interest in recent times due to their various advantageous properties and applications in agriculture. The current study aims to exploit the potential cyanobacterial strains isolated from different locations such as freshwater and soil ecosystems. The potential cyanobacterial isolates were screened based on their multiple plant growth promoting (PGP) attributes such as Indol acetic acid (IAA) production, siderophores, and phosphate solubilization. After the screening of cyanobacteria based on multiple PGP activities, the cyanobacterial strain was identified at the species level as Pseudanabaena foetida RJ1, based on microscopy and molecular characterization using 16S rRNA gene sequencing. The cyanobacterial biomass extract and cell-free extracts are utilized for the synthesis of CuO micronutrient Nanoparticles (NPs). The cyanobacterial strain Pseudanabaena foetida RJ1 possesses plant growth-promoting (PGP) attributes that provide reduction and capping for CuO NPs. The synthesized NPs were characterized and subjected to make a nano-formulation, utilizing the cyanobacteria-mediated CuO NPs along with low-cost zeolite as an adsorbent. The application of cyanobacterial biomass extract and cell-free extract provided an excellent comparative aspect in terms of micronutrient NP synthesis. The NPs in the form of formulations were applied to germinated paddy seeds (Pusa Basmati -1509) with varying concentrations (5, 10, 15 mg/l). Effects of cyanobacteria based CuO NPs on hydroponically grown paddy crops were analyzed. The application of nano-formulations has shown a significant increase in plant growth promotion in rice plants under hydroponics conditions. There is no such type of comparative investigation reported earlier, and NPs of micronutrients can be utilized as a new economic nanofertilizer and can be applied to plants for their growth promotion.