VIEW ARTICLE

Development of Phytophthora megasperma var. sojae in Soybean Roots. R. L. Slusher, Former Graduate Research Assistant, Department of Plant Pathology, University of Illinois, Urbana 61801; J. B. Sinclair, Professor, Department of Plant Pathology, University of Illinois, Urbana 61801. Phytopathology 63:1168-1171. Accepted for publication 4 April 1973. DOI: 10.1094/Phyto-63-1168.

A histological stain was developed which is differentially absorbed by oospores of Phytophthora megasperma var. sojae (PMS) in soybean root tissues. Intracellular hyphae and haustorium-like bodies were detected in PMS-infected root tissues by light-microscope studies. A sand medium favored production of oospores in root tissues of cultivars susceptible (‘Amsoy’), field tolerant (‘Wayne’) and resistant (‘Amsoy 71’) to PMS. Wayne roots had as many oospores and greater dry weight when compared with Amsoy roots. Amsoy 71 roots contained few oospores. Oospores were found in Amsoy 71 roots that overwintered in field soil.