Effects of Host Resistance to Pseudocercosporella herpotrichoides and Foot Rot Severity on Yield and Yield Components in Winter Wheat. T. D. Murray, Assistant Professor, Department of Plant Pathology, Washington State University, Pullman 99164-6430. G. W. Bruehl, Professor Emeritus, Department of Plant Pathology, Washington State University, Pullman 99164-6430. Plant Dis. 70:851-856. Accepted for publication 7 April 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-851.

Yield of winter wheat in plots inoculated with Pseudocercosporella herpotrichoides was inversely related to disease severity. In plots where disease was severe, lodging was greater and yield, tillers per square meter, and 1,000-kernel weight were less than in plots where disease was mild. When disease was relatively mild, yield deficits resulted primarily from fewer tillers per square meter. Host resistance to P. herpotrichoides resulted in less disease and was equivalent to delayed inoculation. With severe disease, resistant cultivars had smaller reductions in tillers per square meter and 1,000-kernel weight than susceptible cultivars under similar conditions. Distribution of tillers in lesion classes revealed that even at severe levels of disease, some healthy tillers remained. Compensation by healthy tillers on plants with diseased tillers may result from reduced competition among tillers or adjacent plants.

Keyword(s): disease resistance, eyespot, strawbreaker foot rot.