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Electron Microscopy of Cell Wall Thickening in Local Lesions of Potato Virus-M Infected Red Kidney Bean. J. C. Tu, Former Postdoctoral Fellow, Department of Plant Science, University of Alberta, Canada, Present address of senior author: Electron Microscope Laboratory, University of Alberta; C. Hiruki, Associate Professor, Department of Plant Science, University of Alberta, Canada. Phytopathology 61:862-868. Accepted for publication 23 February 1971. DOI: 10.1094/Phyto-61-862.

The primary leaves of Red Kidney bean (Phaseolus vulgaris) were mechanically inoculated with an Alberta isolate (AP-1) of potato virus M. Local lesions were sampled for electron microscopy 8 days after inoculation. Thin sections of local lesions revealed an abnormal thickening in the inner portion of secondary cell wall. Thickening was initiated in those cells at the periphery of the necrotic area in the lesion. In these cells, thickening of 5 times or more the normal cell wall was not uncommon in the late stage of development. These cells also showed individual virus particles. Various developmental stages of the thickening are described, and the significance of cell wall thickening to cell-to-cell movement of virus is discussed.