Charcoal rot and root-knot nematode control on faba bean by photosynthesized colloidal silver nanoparticles using bioactive compounds from Moringa oleifera leaf extract

In Egypt, faba bean plants are severely damaged by charcoal rot, caused by Macrophomina phaseolina and root-knot, caused by Meloidogyne incognita. The current study was aimed to control these diseases using silver nanoparticles that were biologically synthesized from Moringa oleifera leaf extract. In this work, silver nanoparticles (AgNPs) were prepared with trisodium citrate as a reducing agent to produce chemo-AgNPs and, using an environmentally eco-friendly method, an aqueous extract of M. oleifera leaves under visible light radiation to produce bio-AgNPs. The obtained colloidal solutions of AgNPs were identified by UV-Visible (UV-Vis) spectral analysis and Transmission Electron Microscopy (TEM) analyses. The antifungal and anti-nematode activities of chemo-and bio-AgNPs as well as an aqueous extract of M. oleifera leaves were checked in vitro against M. phaseolina and M. incognita. The obtained results showed that bio-AgNPs were more effective than chemo-AgNPs. Under greenhouse conditions, bio-AgNPs showed a significant reduction in the incidence of damping-off and charcoal rot caused by M. phaseolina. This treatment also reduced the number of juveniles in the soil, the number of galls and the number of egg-masses of M. incognita in comparison to plants treated with nematodes. Moreover, the protein profile using SDS-PAGE was performed for determining the effect of the studied treatments on the expression of some genes compared with untreated plants the alteration in gene expression led to the formation of different proteins and the loss of others. The proteins which were formed or lost caused a significant variation in all growth and physiological parameters such as photosynthetic pigments, proline content and antioxidant enzymes of faba bean plants.