ABSTRACT
Twenty-three isolates of Rhizoctonia spp. from agronomic crops and turfgrasses were characterized by cytological and pathological methods in order to establish the identity, pathogenicity, and virulence of Rhizoctonia spp. and anastomosis groups that occur on these hosts in Mississippi. Twelve isolates were identified as R. solani, including the five anastomosis groups (AGs) AG-1-IB, AG-2-2, AG-4, AG-5, and AG-13. Rhizoctonia zeae, R. oryzae, and eight binucleate Rhizoctonia sp., including R. cerealis, also were identified. R. solani AG-4 isolates were consistently the most virulent isolates on all hosts in pathogenicity evaluations. Pathogenicity of AG-2-2 and AG-5 isolates, binucleate Rhizoctonia spp., and R. oryzae varied between hosts. Two AG-2-2 isolates from bermudagrass or wheat were determined to be clonal isolates, with numerous self-anastomosis reactions. R. solani (AG-1-IB) was pathogenic on all graminaceous hosts. R. cerealis produced sharp eyespot symptoms on wheat and corn and minimal symptoms on cotton and soybean. This is a first report of R. cerealis as a pathogen of corn. R. zeae isolates were pathogenic on all hosts, including cotton and soybean. These results indicate that a diverse group of Rhizoctonia spp. occurs as pathogens on a wide variety of agronomic crops and turfgrasses in Mississippi.
