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Influence of Temperature on Growth and Pathogenicity of Geographic Isolates of Diaporthe phaseolorum var. caulivora. B. L. Keeling, Research Plant Pathologist, USDA-ARS, Soybean Production Research, Stoneville, MS 38776. . Plant Dis. 72:220-222. Accepted for publication 27 September 1987. 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-72-0220.

The influence of temperature on the growth and pathogenicity of isolates of Diaporthe phaseolorum var. caulivora from northern and southern regions of the United States that cause stem canker disease of soybeans (Glycine max) was compared. The mycelial growth of southern isolates equaled or significantly exceeded that of the northern isolates at temperatures between 10 and 35 C. Growth of northern isolates was significantly inhibited at 30 C, whereas the southern isolates maintained maximum growth rate. Pathogenicity of a southern isolate on soybean seedlings was not affected at temperatures between 21 and 30 C. A northern isolate was almost completely nonpathogenic at 30 C. These differences in effect of temperature on growth and pathogenicity of northern and southern isolates may influence their regional distribution.