Effects of soil infestation with vesicular arbuscular mycorrhizal (VAM) fungi, i.e. Glomus macrocarpum and G. australe, each alone or in combination with the root-rot infecting fungi, i.e. Fusarium solani (Mart) Appel & Wollenav. or Rhizoctonia solani Kuhn, in sterilized and unsterilized soils, on percentage of survived plants, root-rot disease severity index (DSI) and some growth characters of broad bean (Vicia faba L.) cultivars Giza 2 and Ribaya-40 (R-40), were investigated wider greenhouse conditions. Mycorrhizal plants grown in soils infested with F. solani or R solani showed significant increases in percentage of survived plants and reductions in root-rot disease incidence compared with the non- mycorrhizal plants grown with pathogens only. The VAM-fungus, G. macrocarpum was more effective, in this respect, than G. australe and broad bean cultivarR-40 responded better than Giza 2 one especially in unsterilized soil. Root-rot disease incited by F. solani on cv. Giza 2 and R. solani on cv. R-40 were slightly but significantly reduced by introducing G. australe into soils infested with these pathogens. However, double infestation of unsterilized soil with both G. australe and R solani resulted in significant increase in DSI on cv. Giza 2 compared with R. solani alone. Fusarium solani caused considerable increase in colonization intensity of roots by the VAM-fungus G. australe but not G. macrocarpum, while R. solani, in general decreased colonization indexes of both VAM-fungi. Inversed relationships were detected between colonization index of G. macrocarpum only and DSI particularly of F. solani. The lowest values of DSI of F. solani or R. solani and highest colonization index of G. macrocarpum were associated with mycorrhizal plants of cv. R- 40 in unsterilized soil. Soil infestation with G. australe and F. solani or R. solani showed significant higher plant height, root length, shoot and root dry weight than in case of pathogen only. Height and root length of F. solani infected plants, in both soil types were not significantly different from those inoculated with both G. macrocarpum and F. solani Results of this investigation indicate that, soil infestation with VAM-fungi could be promising for controlling root-rot diseases and/or improved growth of broad bean plants. |
