Fusarium solani (Mart.) Appel. & Wollenew. and Rhizoctonia solani Kühn., are reported in this work as broad bean root-rot pathogens, but R. solani is more virulent than F. solani.
Survival percentage was significantly higher in cv. Giza 2 than cv. Ribaya-40 (R-40). Both cultivars survived best in sterilized and unsterilized soils respectively. In absence of root-rot pathogens, survival produced by the vesicular-arbuscular-mycorrhizal Glomus macrocarpum, (VAM) fungus was increased significantly more than Benlate and Mancoper. In VAM-fungicide combinations, survivals were significantly reduced if compared with VAM-fungus alone. In soils infested with F. solani or R. solani, the best survival was produced by Benlate alone or its combination with VAM-fungus, respectively. However, VAM-fungus alone increased survival significantly better than Mancoper fungicide when they were used against R. solani.
Root-rot disease severity index (DSI) was significantly higher in sterilized soil than in unsterilized soil and on cv.. R-40 than cv. Giza 2. The DSI reduced significantly by applying fungicides or VAM-fungus as well as by their combinations. The VAM-fungus alone, was effective as or better than Benlate against root-rot disease incited by R. solani on both cultivars and F. solani on cv. R-40, in unsterilized soils. The VAM-fungus, seems to be less effective against R. solani-infection developed in sterilized soil, especially on cv. R-40. However, VAM-fungicide combinations, in most cases, resulted in significant improvement in disease control if compared with VAM-fungus alone.
The intensity of VAM-colonization to roots of broad bean plants was higher, in general, on cv. R-40 than cv. Giza 2, especially in unsterilized soil. However, it was negatively affected by the tested fungicides and pathogens with few exceptions. In this respect, R. solani inhibited VAM-colonization more than F. solani, and Mancoper fungicide than Benlate fungicide. Root-rot pathogens occurred in unsterilized soil together with VAM-fungus caused greater increases in VAM-colonization compared with the later fungus alone. Increasing in VAM-colonization and reduction in root-rot incited by F. solani seems to be closely related.
Plant height and root length of plants inoculated with VAM-fungus and grown in soils infested or uninfested with root-rot pathogen, were significantly higher than those of non-inoculated plants: Fungicides alone had no effects or exhibited harmful appearance on both plant height and root length of diseased plants. When fungicides used in combination with VAM-fungus both growth characters were significantly improved.