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Interference Microscopy of Onion Epidermal Nuclei in Response to Botrytis allii Infection. F. B. Kulfinski, Associate Professor, Faculty of Biological Sciences, Southern Illinois University, Edwardsville 62025; A. J. Pappelis, Associate Professor, Department of Botany, Southern Illinois University, Carbondale 62901. Phytopathology 61:724-727. Accepted for publication 27 January 1971. DOI: 10.1094/Phyto-61-724.

The nuclear area (NA), nuclear dry mass/cm2 (DM/A), and the total nuclear dry mass (NDM) of host cells (inner epidermis of the equatorial region of onion bulb scale) were determined in three locations (0 through 5 mm, 6 through 10 mm, and 16 through 20 mm) adjacent to a cork-borer wound (sterile or inoculated with Botrytis allii). Inoculation with B. allii resulted in a decrease in NA (72%), DM/A (82%), and NDM (60%) of cells 0-5 mm from the site of inoculation when compared with those 16-20 mm from this site (48-hr incubation) within the same bulbs. It also resulted in decreases of NA (71%), DM/A (96%), and NDM (69%) in cells from inoculated bulbs 0-5 mm from the site of inoculation when compared with these characteristics for nuclei of cells in the same location in noninoculated sites. Wounding induced an NA increase (104%) and DM/A and NDM decreases (87 and 93%, respectively) in nuclei of cells 0-5 mm away from the wounding site when compared with those 16-20 mm away. We conclude that B. allii secretes substances which induce nuclear pycnosis in host cells.