Silver nanoparticles for control of foliar pathogens in passion fruit (Passiflora edulis) crops

Sustainable management of phytopathogens has driven the use of metallic nanoparticles due to their high antimicrobial efficacy, stability and environmental compatibility. In this work, we investigate the antimicrobial action of silver nanoparticles mycosynthesized against pathogens of yellow passion fruits (Passiflora edulis). Pathogen selection involved field sampling, isolation, and reinfection assays, confirming the presence of Cladosporium cladosporioides and Colletotrichum theobromicola. as well as investigated the bacterium Xanthomonas axonopodis pv. passiflorae. The AgNPs were mycosynthesized using the endophytic extract of Aspergillus brasiliensis and co-stabilized by carboxymethyl cellulose, and characterized by structural, morphological and interfaces techniques, exhibiting important physicochemical characteristics as diameter of 18.78 nm, and zeta potential of −23.41 mV. The in vitro assays demonstrated the inhibitory effect of AgNPs for mycelial growth of C. cladosporioides and C. theobromicola, with dose-dependent response, reaching inhibition exceeding 80 % for 60–100 μg mL⁻¹. Concentrations above 20 μg mL⁻¹ effectively inhibited the conidial germination. Electron microscopies revealed structural damage to hyphae and cell wall fungi. For Xanthomonas axonopodis pv. passiflorae, the minimum inhibitory concentration (MIC) was 20 μg mL⁻¹, and the minimum bactericidal concentration (MBC) was 60 μg mL⁻¹. These results underscore the potential of mycosynthesized nanoparticles as antimicrobial agents, presenting a promising alternative for the management of passion fruit diseases. The importance of in vitro studies is also highlighted as a methodology for understanding the action of nanoparticles under controlled conditions, allowing the pre-selection of candidates and the definition of boundary conditions, improving the design of in vivo experiments.