Bio-Fabrication of ZnONPs from Alkalescent Nucleoside Antibiotic to Control Rice Blast: Impact on Pathogen (Magnaporthe grisea) and Host (Rice)

In the traditional method of the bio-fabrication of zinc oxide nanoparticles (ZnONPs), bacterial strains face metal toxicity and antimicrobial action. In the current study, an alkalescent nucleoside antibiotic was mixed with zinc hexanitrate to fabricate the ZnONPs. An integrated approach of DIAION HP-20 macroporous resin and sephadex LH-20 column chromatography was adopted to separate and purify alkalescent nucleoside AN03 from Streptomyces koyanogensis. Alkalescent nucleoside was confirmed by the Doskochilova solvent system. The bio-fabricated ZnONPs were characterized by using Fourier transform infrared (FTIR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) analyses. The XRD spectrum and the TEM images confirmed the crystallinity and the spherical shape of the ZnONPs with an average size of 22 nm. FTIR analysis showed the presence of functional groups, which confirmed the bio-fabrication of ZnONPs from alkalescent nucleoside ANO3. In-vitro studies showed that 75 μg/mL of ZnONPs had a strong inhibitory zone (28.39 mm) against the Magnaporthe grisea and significantly suppressed the spore germination. SEM and TEM observations respectively revealed that ZnONPs caused breakage in hyphae and could damage the cells of M. grisea. Greenhouse experiments revealed that the foliar spray of ZnONPs could control the rice blast disease by 98%. Results also revealed that ZnONPs had positive effects on the growth of the rice plant. The present study suggested that ZnONPs could be fabricated from microbe-derived nucleoside antibiotics without facing the problems of metal toxicity and antimicrobial action, thus overcoming the problem of pathogen resistance. This could be a potent biocontrol agent in rice blast disease management.