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Histopathology of Cercospora sojina in Soybean Seeds. Tribhuwan Singh, Assistant professor of botany and visiting research associate, Department of Plant Pathology, University of Illinois at Urbana-Champaign (UIUC), Urbana 61801, Department of Botany, University of Rajasthan, Jaipur, 302004, India; J. B. Sinclair, Professor of plant pathology, Department of Plant Pathology, University of Illinois at Urbana-Champaign (UIUC), Urbana 61801. Phytopathology 75:185-189. Accepted for publication 6 September 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-185.

Soybean seeds were collected from plants either uninoculated or inoculated separately with one of eight isolates of Cercospora sojina. Seeds infected by C. sojina were discolored gray to dark brown. Histopathological and scanning electron microscope studies showed the presence of hyphae of C. sojina within the seed coat tissues of seeds from plants inoculated with all but one isolate. The fungus penetrated seeds both indirectly through pores and cracks in the seed coat and directly through hilar tracheids. In seeds inoculated with four of the isolates and in infected seeds from naturally inoculated plants, hyphal mats in parenchymatous seed coat tissues as well as hyphal aggregates, which varied in size and number, were associated with fungal hyphae. Hyphal aggregates were abundant in the hilar region, moderately common in the seed coat layers, found occasionally on the seed surface and in the space between the seed coat and embryo, and rarely observed in the hypocotyl-radicle axis. Fungal infection was not found in the cotyledons. Hyphae without hyphal aggregates were found in seeds from plants inoculated with three of the isolates.

Additional keywords: Cercospora kikuchii, Glycine max, Phomopsis spp.