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Characterization of Rhizoctonia Species Isolated from Ornamentals in Florida. A. R. Chase, Professor of Plant Pathology, University of Florida, IFAS, Central Florida Research and Education Center, Apopka 32703. Plant Dis. 75:234-238. Accepted for publication 31 July 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0234.

Rhizoctonia species were collected from Florida ornamental plants and characterized by nuclear condition and anastomosis grouping. Of 309 isolates, 126 (41%) were collected from roots, 77 (25%) from stems, and 106 (34%) from leaves. Of 129 multinucleate isolates, 43 (33%) were R. solani and 4 (3%) were R. zeae collected from roots, 30 (24%) were R. solani from stems, and 52 (40%) were R. solani from leaves. Of the isolates of R. solani, approximately 60% were from anastomosis group 4 (AG-4), 20% were AG-1 (all from leaves), and 20% could not be typed to the first four anastomosis groups. The remaining 180 isolates were binucleate organisms, 60 (34%) of which were isolated from leaves, 42 (23%) from stems, and 78 (43%) from roots. The majority of isolates of R. solani but only a small percentage of binucleate isolates were pathogenic to their hosts of origin. Isolates of R. solani AG-4 were pathogenic on a wide range of herbaceous ornamentals.