Effectiveness of bimetallic ZnO-B2O3 nanoparticles produced by Streptomyces gancidicus as prospective antifungal agents and therapeutic nutrients to enhance pea plant immunity against damping off-causing Pythium irregulare: in vivo and in vitro investigations

Abstract

Pythium irregulare (P. irregulare) is one of the soil-borne pathogens that is the primary cause of damage to several plants each year. The novelty and originality of this work were the ability of Streptomyces gancidicus (S. gancidicus OR229936) to synthesize bimetallic zinc oxide-boron oxide nanoparticles (ZnO-B2O3 NPs) for reducing P. irregulare growth and safeguarding pea plant from damping off disease. The produced bimetallic ZnO-B2O3 NPs’ XRD results highlighted the ZnO diffraction peaks at 2Ɵ = 27.50°, 31.15°, 45.15°, 56.89°, 67.98°, and 75.25°, which are complemented by the standard card JCPDS number 361451 and correspond to (002), (101), (102), (110), (103), and (201) Bragg’s reflections. Along with the standard card JCPDS number 300019, they additionally include the B2O3 NP diffraction peaks at 2Ɵ = 15.25°, 28.69°, 31.99°, and 41.28°. Bimetallic ZnO-B2O3 NPs were tested against P. irregular for their antifungal activities. The findings indicated that ZnO-B2O3 NPs exhibited potential anti P. irregulare activity, with an inhibition zone of 33 mm at a concentration of 1000 µg/mL and a promising MIC of 0.01 µg/mL. Bimetallic ZnO-B2O3 NPs (0.01 ppm) application appeared to significantly lessen the severity of the pea post-emergence damaging off disease by 10% and to provide significant protection by 88%. In comparison to fungicide (difenoconazole 25%) treatments, all metabolic resistance indicators significantly enhanced after the usage of bimetallic ZnO-B2O3 NPs, ZnO NPs, and B2O3 NPs with ethyl acetate extract of S. gancidicus. The beneficial impacts of the bimetallic ZnO-B2O3 NPs, ZnO NPs, and B2O3 NPs have been broadened to increase the enzyme activities of peroxidase (POD) and polyphenol oxidase (PPO) in both healthy and infected pea plant in comparison to control. Reduction of Malondialdehyde content (MDA) in response to S. gancidius filtrate, bimetallic ZnO-B2O3 NPs, ZnO NPs, B2O3 NPs, and difenoconazole by 41.68%, 36.51%, 26.15, 26.15, and 15.25%, respectively. Also, contents of H2O2 in infected pea plant were diminished by 50%, 45%, 40%, 37.5%, and 22.5% at bimetallic ZnO-B2O3 NPs, S. gancidicus filtrate, ZnO NPs, difenoconazole, and B2O3 NPs comparing to P. irregular-infected pea plant is strong evidence to induce disease recovery. The application of bimetallic ZnO-B2O3 NPs seems to be a significant approach to relieve the toxic influences of P. irregulare on infected pea plant as green and alternative therapeutic nutrients of chemical fungicides.