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Cytology and Histology

Relation Between Foliar Symptoms and Systemic Advance of Cephalosporium gramineum During Winter Wheat Development. J. B. Morton, Department of Plant Pathology, Montana State University, Bozeman 59717, Current address of senior author: Cargill PAG Research, P.O. Box 146, Lubbock, TX 79408; D. E. Mathre(2), and R. H. Johnston(3). (2)(3)Department of Plant Pathology, Montana State University, Bozeman 59717. Phytopathology 70:802-807. Accepted for publication 1 March 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-802.

Systemic spread of the vascular pathogen, Cephalosporium gramineum, was characterized relative to anatomical and developmental features of its winter wheat (Triticum aestivum) host. Pathogen restriction was associated with xylem maturation gradients between internodes, within nodes, and within leaves. Restriction of symptom development also was attributed to increased gelation and gummosis within the xylem and/or to inhibition of fungal sporulation. All evidence suggested that this pathogen is incapable of penetrating living cells at any time during the disease cycle. The number and pattern of vascular bundles in different winter wheat cultivars and the temporal association between pathogen colonization and symptom induction formed the basis for a disease index rating system. Both the movement and distribution of C. gramineum and the disease index rating system have practical implications in a germplasm development program. The former emphasizes the need to separate rate of disease development from rate of host development in evaluating winter wheat genotypes. The latter provides a valuable tool for monitoring symptom expression within and among plants of different genotypes.