HISTOPATHOLOGY OF TOMATO LEAVES INOCULATED BY XANTHOMONAS PV VESICATORIA

Xanthomonas campestris pv vesicatoria infection was followed by light and scanning electron microscopy. Bacteria entered leaf tissue through stomata and multiplied in substomatal chambers which are additional survival sites. The pathogen could also enter through the open base of trichomes. X c pv vesicatoria colonized the intercellular spaces of spongy parenchyma and could reach the uninvaded substomatal chambers and, after extensive multiplication, masses of bacterial cells, agglutinated in a mucous substance, extruded through stomata being the cause of secondary sources of inoculum. Abaxial leaf surfaces contained more bacteria than adaxial tomato leaf surfaces. Stomata and substomatal chambers were the preferred ecological niches of X c pv vesicatoria before tissue colonization.