Anastomosis Group 3 Is the Major Cause of Rhizoctonia Disease of Potato in Maine. B. P. Bandy, Research Assistant, Department of Botany and Plant Pathology, University of Maine, Orono 04469. S. S. Leach, and S. M. Tavantzis. Research Plant Pathologist, USDA-ARS, Orono; Associate Professor, Department of Botany and Plant Pathology, University of Maine, Orono 04469. Plant Dis. 72:596-598. Accepted for publication 10 February 1988. 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, 1988. DOI: 10.1094/PD-72-0596.

Three hundred seven isolates of Rhizoctonia solani associated with stem and stolon canker and black scurf of potato in Maine were characterized with regard to anastomosis group (AG). The results confirmed that members of AG-3 are the major cause of Rhizoctonia disease of potato in fields surveyed. One hundred percent of the isolates from tuberborne sclerotia and 82.1% of the isolates from stem and stolon lesions were members of AG-3. The most important non-AG-3 isolates were members of AG-5, which comprised 13.4% of the cultures isolated from stem and stolon lesions. Anastomosis group 2, type 1, associated with potato in other geographic areas, was not isolated from sclerotia, nor from infected plants in Maine.