Soybean Stem Canker Incited by Isolates of Diaporthe and Phomopsis spp. from Cotton in Mississippi. K. W. Roy, Associate Professor, Department of Plant Pathology and Weed Science, Mississippi State University, Mississippi State 39762. W. A. Miller, Graduate Research Assistant, Department of Plant Pathology and Weed Science, Mississippi State University, Mississippi State 39762. Plant Dis. 67:135-137. Accepted for publication 16 June 1982. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-135.

Isolates of Diaporthe and Phomopsis spp. from cotton (Gossypium hirsutum) leaves and seedlings were inoculated into soybean (Glycine max) stems in the field by using a stem-puncture technique. All isolates incited cankers by the eighth week after inoculation. Isolates differed in virulence on soybean. Girdling and nongirdling cankers ranging in length from 0.5 to 12.6 cm, internal stem necrosis, interveinal necrosis of leaves, and killing of plants were associated with infection by these isolates. Plants inoculated with Diaporthe phaseolorum var. caulivora from soybean exhibited similar symptoms. Data indicate that cotton may serve as a source of inoculum for these fungi, which are potentially capable of inciting stem canker of soybean.