Alleviation of Rhizoctonia root rot damage in common bean by some arbuscular mycorrhizal fungi

Rhizoctonia root rot of common bean (Phaseolus vulgaris) caused by Rhizoctonia solani is among the most important soil-borne fungal diseases worldwide. In this study, nine arbuscular mycorrhizal fungi (AMF) including Acaulospora longula, Funneliformis mosseae, Gigaspora margarita, Glomus caledonium, G. claroideum, G. etunicatum, G. fasciculatum, G. versiform and Rhizophagus irregularis were evaluated for their effect on some growth traits and inhibition of R. solani in bean plants under greenhouse conditions. Six AMF species (F. mosseae, G. claroideum, G. etunicatum, G. margarita, G. caledonium and G. versiform) significantly reduced the disease severity index and the first four of these also reduced the incidence of disease compared with the infected control. The lowest disease severity and incidence were obtained by F. mosseae and G. claroideum, respectively. Compared with the infected control, the root length was significantly improved by all AMF. The other growth traits were also significantly improved by all AMF species with some exceptions as follows: root wet and dry weights (except G. fasciculatum), shoot wet weight (excep G. versiform), shoot length (except G. claroideum, G. versiform and G. etunicatum) and shoot dry weight (except G. etunicatum, G. fasciculatum, G. caledonium and G. margarita). Glomus fasciculatum had the highest root colonization. According to the results of this study, many AMF fungi improved plant growth and partially compensated for Rhizoctonia root rot on common bean, and they could be considered as good candidates for studying the biological control of this disease under field conditions.