Biosynthesis of Zinc Nanoparticles Using Endophytic Fungi and Olive Mill Wastes and Its Activity against Some Plant Pathogenic Fungi

Abstract

Soil-borne fungal pathogens represent a major threat to potato cultivation, particularly under arid conditions where disease management options are limited. This study aimed to explore the dual role of endophytic fungi as both biocontrol agents and biofactories for zinc nanoparticles (ZnNPs), providing an eco-friendly approach to disease suppression. Sixty symptomatic potato plants were collected from Mut and Balat, New Valley Governorate, Egypt. Six pathogenic fungi were isolated and identified, with Fusarium oxysporum, F. moniliforme, and Rhizoctonia solani showing the highest virulence in greenhouse assays. In parallel, twenty-two endophytic fungal isolates were obtained from healthy potato plants and screened for pathogenicity. All proved non-pathogenic were further evaluated for antagonistic activity against the pathogens. Trichoderma sp. and Penicillium sp. displayed the highest inhibition rates in dual culture assays, while Fusarium spp. and Aspergillus sp. were selected for ZnNPs biosynthesis due to their moderate antagonistic potential and superior nanoparticle production capacity. ZnNPs were synthesized using both fungal biomass and olive mill
waste (OMW) and characterized via UV–Visible spectrophotometry, with absorption peaks ranging from 365 to 390 nm. In vitro assays revealed that endophyte-derived ZnNPs (EF-ZnNPs) had significantly higher antifungal activity than OMW-derived ZnNPs, especially at 150 ppm concentration. EF-ZnNPs inhibited radial growth and reduced dry mycelial weight of pathogens more effectively. Greenhouse trials confirmed that EF-ZnNPs reduced disease severity by up to 68% and decreased rhizosphere fungal load by over 50%, while also improving plant growth performance. These findings highlight the potential of endophytic fungi as a sustainable tool for disease control in potato cultivation, combining direct antagonism and nanotechnology-based intervention. Further studies on biosafety and environmental impact are recommended to support field-scale application.