Effect of Soil Temperature on Infection of Soybean Roots by Sclerotia-Forming Isolates of Colletotrichum truncatum. Mahmood Khan, Department of Plant Pathology, University of Illinois at Urbana-Champaign, 1102 S. Goodwin Avenue, Urbana 61801-4709. J. B. Sinclair, Department of Plant Pathology, University of Illinois at Urbana-Champaign, 1102 S. Goodwin Avenue, Urbana 61801-4709. Plant Dis. 75:1282-1285. Accepted for publication 24 July 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-1282.

Soybean (Glycine max) cvs. A. K. (Kansas), Boone, and Williams 82 were grown in sand infested with sclerotia from two sclerotia-forming isolates of Colletotrichum truncatum in soil temperature tanks at 20, 25, 30, or 35 C and at greenhouse ambient temperature (21–28 C). Root and hypocotyl infection were recorded on all cultivars at all temperatures. Lesion size and number generally increased with an increase in soil temperature up to 30 C and then declined. Williams 82 had the highest disease rating, Boone the lowest, and A. K. (Kansas) was intermediate over all temperatures.