Effectiveness of Epicoccum nigrum and Silver Nanoparticles in Controlling Chocolate Spot Disease and Enhancing Growth and Yield of Faba Bean (Vicia faba L.)

Abstract

Chocolate spot disease caused by Botrytis fabae is the most common fungal disease of faba bean (Vicia faba) in all its cultivation areas. This study tested the effectiveness of Epicoccum nigrum as a biocontrol agent and silver nanoparticles (AgNPs) for controlling chocolate spot disease. The characterization of AgNPs was carried out by UV-visible spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD). A maximum absorption peak is visible in the UV-visible spectrum at 400 nm. TEM images revealed that the AgNPs have a spherical-like shape in the micrograph and their average size is 45 ± 5 nm. XRD of AgNPs shows six clear reflections in the diffractogram were observed at 38.15^o, 44.39^o, 64.55^o and 77.73, 81.71^o and 98.35^o. In in vitro studies, eleven local isolates of E. nigrum and AgNPs at different concentrations (20, 40, 80 and 100 ppm) were assessed on the mycelium growth of B. fabae in the laboratory. The antagonistic results showed that the E. nigrum fungus isolates had a high ability to inhibit the pathogen’s growth to varying degrees. AgNPs, at a concentration of 100 ppm, inhibited the pathogenic fungus B. fabae by 75.93%. Foliar applications of E. nigrum and AgNPs reduced the disease severity of chocolate spot in both greenhouse and field, with AgNPs being the most effective in reducing the disease severity compared to the control. Data also showed that all of the studied agronomic traits, including plant height (cm), number of pods per plant and weight of 100 seeds (gm) were significantly increased by the application of these treatments. In comparison to untreated plants, all treatments significantly increased total phenol contents and peroxidase enzyme activity in treated plants. From the results, we conclude that E. nigrum and AgNPs were successful in protecting faba bean plants against chocolate spot disease, as well as improving growth and yield.