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Correlation of Cultural Characters and Source of Isolates with Pathogenicity of Rhizoctonia solani from Sugar Beet. E. G. Ruppel, Research Plant Pathologist, Plant Science Research Division, ARS, USDA, Crops Research Laboratory, Colorado State University, Fort Collins 80521; Phytopathology 62:202-205. Accepted for publication 1 September 1971. DOI: 10.1094/Phyto-62-202.

A crown and two foliar isolates of Rhizoctonia solani from sugar beet exhibited significantly greater growth rate in culture than did six root isolates. Root isolates were assignable to anastomosis group 2, whereas the crown and foliar isolates were associated with group 4. In pathogenicity studies, all isolates incited significant damping-off; crown and foliar isolates caused significantly more foliar blight than did root isolates, with the crown isolate being intermediate; and root isolates caused more severe root rot than did the crown or foliar isolates. Disease reactions were significantly more severe in a susceptible cultivar (GW 674-56C) as compared with a resistant selection (FC 701/2) from GW 674-56C in damping-off and root rot tests. Root isolates × lines interactions were nonsignificant, which indicated that resistance of FC 701/2 is effective against several diverse isolates of the pathogen.

Additional keywords: Beta vulgaris; crown rot.