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Virulence of Cephalosporium gregatum and Verticillium dahliae in Soybeans. H. Tachibana, Research Plant Pathologist, Crops Research Division, ARS, USDA, Department of Botany and Plant Pathology, Iowa State University, Ames 50010; Phytopathology 61:565-568. Accepted for publication 16 December 1970. DOI: 10.1094/Phyto-61-565.

Verticillium dahliae was isolated from diseased soybean plants, and subsequently proved pathogenic to soybeans. Verticillium dahliae produced vascular discolorations similar to those caused by Cephalosporium gregatum but did not produce typical brown stem rot symptoms caused by C. gregatum. Leaf symptoms produced by the two fungal pathogens were distinct. When soybean cultivars resistant and susceptible to C. gregatum were inoculated with V. dahliae, they were similarly resistant and susceptible. Midwest and Ontario were the most resistant and susceptible cultivars, respectively. Average infection percentage for nine cultivars decreased from 82.9 at 18 C to 49.8 at 28 C when plants were inoculated with C. gregatum. Infection decreased only slightly, from 97.1% at 18 C to 94.4% at 28 C, when plants were inoculated with V. dahliae. Average length of vascular tissue discoloration was similar at 18 and 28 C for C. gregatum, while plants inoculated with V. dahliae had slightly more discoloration at the higher temperature. Plant height reduction was greater with V. dahliae- than with C. gregatum-inoculated plants.

Additional keywords: Glycine max, symptoms.