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Ecology and Epidemiology

Root Cortical Death in Relation to Infection of Kentucky Bluegrass by Phialophora graminicola. R. W. Smiley, Associate professor, Department of Plant Pathology, Cornell University, Ithaca, NY 14853, First author is currently superintendent and professor of plant pathology, Columbia Basin Agricultural Research Center, Oregon State University, Pendleton 97801; D. E. Giblin, former student, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. Phytopathology 76:917-922. Accepted for publication 23 April 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-917.

The influence of temperature and shading on natural autolysis of nuclei in root cortex cells, a process called root cortical death, was examined in Merion Kentucky bluegrass (Poa pratensis). The process was also studied in four cultivars (Adelphi, Merion, Nassau, and Nugget) of Kentucky bluegrass grown at three temperatures and two light intensities, in the presence or absence of the high-temperature root-infecting pathogen Phialophora graminicola. The magnitude of root cortical death in seedlings differed for each cultivar x temperature x light intensity interaction. The process generally occurred faster at 29 C than at 14 or 24 C, and shading reduced the rate of anucleation at 29 C in all cultivars except Adelphi. Numbers of functional nuclei in root cortices were inversely correlated (P=0.05) with percentages of root area colonized by the pathogen and with degree of root blackening and directly correlated with quality of turfgrass foliage. Root cortical death assessments in Kentucky bluegrasses may be useful in breeding and selecting cultivars with improved resistances to root pathogens and environmental stresses.