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Characterization of Isolates of Rhizoctonia solani from Lima Beans Grown in New York State. Helene R. Dillard, Assistant professor, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456; Phytopathology 77:748-751. Accepted for publication 17 November 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-748.

In 1984, a pod rot was observed on lima beans grown in western New York State. Reddish brown, sunken lesions frequently developed on pods in contact with the soil surface. The seeds within the affected pods were discolored tan to reddish brown. Rhizoctonia solani was isolated from discolored seeds and pods. Inoculation of intact lima bean pods or detached seeds with sclerotial masses or with potato-dextrose agar disks colonized for 3 days by the isolates of R. solani produced lesions similar to those observed in the field. Hyphal tip cells of all isolates were multinucleate, had dolipore septa, and belonged to anastomosis groups 1 and 5. The sexual stage (Thanatephorus cucumeris) of anastomosis group 1 (microsclerotial-type) isolates was induced in the laboratory using a nutrient stepdown technique. In greenhouse studies, all isolates were pathogenic to lima bean hypocotyls and produced web blight symptoms at high relative humidities.