The arbuscular mycorrhizal (AM) fungal preparations that were used during this study were obtained from the Department of Plant Pathology, Faculty of Agriculture, Al-Azhar University (Assiut
Branch), Egypt. The G. mosseae commercial product of AM fungus was prepared by extracting the spores from soils according to Gerdemann and Nicolson (1963) and propagating them on the appropriate host onion plant (Allium cepa) as described by Khalifa (1997). G. mosseae was used at a rate of 10 g/kg soil with the top 10 cm of soil surface before inoculation with the BW pathogen. Mycorrhiza were preserved in corn (Zea mays) and onion (A. cepa) in pot culture in the greenhouse for future studies.
Based on the in vitro plant oil screening results, two oils (thyme and peppermint) were selected to further analyze their effects under greenhouse conditions against the pathogen. The selected oils were used at 1:100 v/v concentrations.