Soybean Germ Plasm Evaluation for Resistance to Colletotrichum truncatum. J. B. Manandhar, Former Graduate Research Assistant, Department of Plant Pathology, University of Illinois at Urbana-Champaign, 1102 S. Goodwin Avenue, Urbana 61801. G. L. Hartman, and J. B. Sinclair. Graduate Research Assistant, and Professor, Department of Plant Pathology, University of Illinois at Urbana-Champaign, 1102 S. Goodwin Avenue, Urbana 61801.. Plant Dis. 72:56-59. Accepted for publication 29 July 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0056.

The number of conidia per square centimeter of potato-dextrose agar (PDA) disk produced by Colletotrichum truncatum, cause of soybean (Glycine max) anthracnose, and its pathogenicity on soybean seedlings varied among seven isolates. Isolate Ct-1 from soybeans produced more conidia than other isolates and was highly pathogenic on inoculated soybean seedlings and seeds. Foliar anthracnose in susceptible plants inoculated with a conidial suspension of isolate Ct-1 progressed curvilinearly with increased time in a mist chamber. Seedlings inoculated at the V1 growth stage were killed within 72 hr. Plants inoculated at the V2, V6, and R4 growth stages were defoliated within 72 hr. Necrosis in stem tips occurred most often at V2, intermediately at V6, and least at R4 growth stages. Disease development and survival of C. truncatum in soybean cultivars remained high after 0–98 hr under dark conditions but decreased with increasing periods under light conditions. None of the 414 germ plasm accessions of maturity groups 000–X inoculated at the V1 growth stage and evaluated for foliar anthracnose was immune. Several lines in maturity groups 00–IV, PI 96.860 (maturity group VI), and Tarheel Black (maturity group VII) were resistant.

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