Protective role of iron oxide nanocomposites on disease index, and biochemical resistance indicators against Fusarium oxysporum induced-cucumber wilt disease: In vitro, and in vivo studies.

Recently nanocomposites have become a super-growth inducers as well as vital antifungal agents, which enhance plant growth and suppress plant diseases. A new strategy regarding the fabrication of humic acid (H) and boron (B) conjugated FeO nanocomposites was performed. FeO NP-B and FeO NP-H were synthesized in the presence of gamma-rays (as a direct reducing agent). Gamma-rays provoked reduction of metal ions due to the liberated reducing electrons, (e), in aqueous solutions which can be considered as a direct reduction. Antifungal potential against Fusarium oxysporum, the causative agent of wilt disease in cucumber was determined. Disease index percent, metabolic resistance indicators in cucumber plant as response to promotion of systemic resistance (SR) were recorded. Results illustrated that both FeO NPs-B and FeO NPs-H nanocomposites had antifungal activity against F. oxysporumin vitro as well as in vivo. Results revealed that minimum inhibitory concentrations of FeO NPs-B and FeO NPs-H nanocomposites were 0.25 and 0.125 mM, respectively. Application of FeO NPs-B (0.25 mM) and FeO NPs-H (0.125 mM) appeared highly reduced the cucumber wilt disease symptoms incidence caused by F. oxysporum, and recorded disease severity by 83.33%. FeO NPs-B was the best treatment reducing disease indexes by 20.83% and gave highly protection against wilt disease by 75.0% and came next FeO NPs-H which reduced disease indexes by 25% and gave 69.99% protection against disease. FeO NPs-B and FeO NPs-H treatments improved morphological traits, photosynthetic pigments, osmolytes, total phenol and antioxidant enzymes activities in both infected and non-infected plants. The beneficial effects of the synthesized FeO NPs-B and FeO NPs-H nanocomposites were extended to increase not only the total phenol, and total soluble protein contents but also the activities of peroxidase (POD), and polyphenol oxidase (PPO) enzymes of the healthy and infected cucumber plants in comparison with control.