Histopathology of bacterial gall of Japanese Wistaria (Wistaria floribunda)

Abstract

Tumor development in wistaria gall caused byErwinia milletiae, (Kawakami and Yoshida) Magrou was observed under a microscope. Hypertrophied cells were observed near wounds 3 days after inoculation. Active cell divisions subsequently occurred in the hypertrophied cells resulting in many daughter cells with thin cell walls, large intensely stained nuclei, and less vacuolated, dense cytoplasm. Hyperplasia occurred often in the concentric arrangements around large bacterial fissures. These cell groups, which were commonly found in phloem, were considered to be the elementary unit tissue of the tumor. With the development of each unit tissue, the surrounding parenchyma tissues appeared to be markedly compressed. The hyperplastic cells near cambium differentiated into the tracheal elements which developed later into vascular bundles extending to the gall tissues. When the tumor tissues further proliferated with a rapid increase in dimensions, the tumor finally erupted out of the periderm of the stem forming a visible gall. The gall tissues were quite different from those of the root nodules caused byRhizobium sp. in that they had an absence of periderm, the full development of the tracheal elements, the diversity of cells in both size and shape, and the multiplication of the pathogenic bacterium in the intercellular spaces.