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Cytology and Histology

A Histological Comparison of the Response of a Chrysanthemum Cultivar Susceptible to Erwinia chrysanthemi and E. carotovora subsp. carotovora. Barbara White Pennypacker, Research associate, Department of Plant Pathology, The Pennsylvania State University, University Park 16802; Robert S. Dickey(2), and Paul E. Nelson(3). (2)Professor, Department of Plant Pathology, Cornell University, Ithaca, New York 14853; (3)Professor, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Phytopathology 71:138-140. Accepted for publication 20 June 1980. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-138.

A comparison was made between the response of Chrysanthemum morifolium ‘Giant #4 Indianapolis White’ to Erwinia carotovora subsp. carotovora and its response to E. chrysanthemi. Both of these organisms caused bacterial blight symptoms in chrysanthemum under favorable conditions. Histological studies revealed that these pathogens caused almost identical anatomical changes in the host plant. Vascular bundle maceration followed by extensive pith cell breakdown occurred in plants inoculated with either of these Erwinia species. Histochemical tests indicated that enzymatic degradation of the middle lamella was probably the primary mechanism responsible for cell breakdown and plant collapse in both cases.