Nine isolates of Trichoderma were collected from Assiut Governorate, Egypt, as leaf surface and endophytic fungi associated with onion flora stalks. Four isolates were identified as Trichoderma harzianum, while five isolates were belonging to Trichoderma longibrachiatum. The antagonistic activity of these isolates against onion purple blotch pathogen Alternaria porri was studied in vitro using dual culture assay. All tested Trichoderma isolates showed mycoparasitic activity and competitive capability against the mycelial growth of A. porri. Mycoparastic activity of Trichoderma was manifested morphologically by the overgrowth upon the mycelial growth of the pathogen and microscopically by production of coiling hyphae around pathogen hyphae. Isolates of T. harzianum exhibited high ability to compete on potato dextrose agar (PDA) medium causing the maximum rate of pathogen inhibition (73.12%), while isolates of T. longibrachiatum showed inhibition rate equalling 70.3%. Chitinase activity of Trichoderma was assayed, and T. harzianum Th‐3013 showed the maximum value contributing 2.69 U/min. Application of T. harzianum Th‐3013 to control purple blotch disease in vivo under greenhouse conditions caused disease reduction up to 52.3 and 79.9% before and after 48 h of pathogen inoculation, respectively, while the fungicide Ridomil Gold Plus caused disease reduction comprising 56.5 and 71.7%, respectively. This study proved that T. harzianum Th‐3013 as a biocontrol agent showed significant reduction in onion purple blotch disease compared with the tested fungicide.

Mycogenic synthesis of silver nanoparticles (AgNPs) was carried out in the present investigation using an aqueous extract of endophytic non-pathogenic Alternaria solani F10 (KT721914). The mycosynthesized AgNPs were characterized by means of spectroscopic and microscopic techniques. The surface plasmon resonance found at 430 nm confirmed the formation of stable AgNPs for several weeks at room temperature. Also, the results revealed the formation of spherical and monodispersed AgNPs with an average size of 14.8 ± 1.2 nm. The FT-IR spectrum suggested that the fungal extracellular proteins and secondary metabolites had the role in Ag reduction and AgNPs capping of which protein Ag nanoconjugates were formed. Furthermore, the mycosynthesized AgNPs exhibited potent antifungal activity against different pathogenic isolates of the same Alternaria solani fungus, the causal pathogen of tomato early blight disease. The antifungal efficiency of the AgNPs at 1, 5 and 10 ppm were evaluated for 8 days after incubation by measuring the inhibition rate of fungal radial growth. The results were further supported by investigating fungal hyphae morphology alteration by scanning and transmission electron microscopy. Treated fungal hyphae showed formation of pits and pores. Also, the mycosynthesized AgNPs were able to pass and distribute throughout the fungal cell area and interact with the cell components.

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The present study is dealing with an ecofriendly and green biological route for extracellular biosynthesis of silver nanoparticles (AgNPs) using the endophytic fungus Cladosporium sphaerospermum F16 (KU199685). The biosynthesised AgNPs were characterised using ultraviolet-visible spectroscopy (UV-vis), transmission electron microscopy (TEM), dynamic light scattering (DLS), energy-dispersive X-ray analysis (EDX) and X-ray diffraction (XRD). The results showed the formation of stable, well-dispersed and spherical crystalline AgNPs with an average size 15.1 ± 1.0 nm and zeta potential of about −41.2 ± 0.5 mV. Optimisation of AgNPs synthesis prepared under different reaction conditions such as: pH, temperature, silver nitrate concentration and time of synthesis reaction to increase the AgNPs production. Meanwhile, the optimum conditions for maximum AgNPs production were pH (7), silver nitrate (5 mM) and incubation time (5-7 days). Interestingly, the fungal exo-metabolities were found to reduce silver ions into AgNPs within10 min after heating the reaction mixture (50-70 °C) as indicated by the developed reddish brown color compared to 30 min under room temperature.

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