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Etiology of Sorghum Sheath Blight and Pathogen Virulence on Rice. N. R. O’Neill, Research Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705. M. C. Rush, Professor, Department of Plant Pathology, Louisiana State University, Baton Rouge 70803. Plant Dis. 66:1115-1118. Accepted for publication 19 March 1982. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1982. DOI: 10.1094/PD-66-1115.

A leaf and sheath blight of sorghum (Sorghum bicolor) occurring in 1975, 1976, and 1977 in Louisiana was caused by Rhizoctonia solani. This pathogen, which belongs to anastomosis group 1, is identical to the fungus that causes aerial blight of soybean (Glycine max) and sheath blight of rice (Oryza sativa). The perfect state of the pathogen, Thanatephorus cucumeris, was found on the foliage of sorghum in several fields. Homokaryotic, single-basidiospore isolates from sorghum varied in cultural characteristics and in virulence to rice cultivars. Virulence of these isolates on sorghum and rice was generally low when compared with heterokaryotic isolates found in the field. Rice cultivars were ranked similarly in disease reaction when inoculated with single-basidiospore isolates or heterokaryotic isolates from sorghum.