TRANSMISSION ELECTRON-MICROSCOPY OF SUSCEPTIBLE AND RESISTANT TOMATO LEAVES FOLLOWING INFECTION WITH PSEUDOMONAS-SYRINGAE PV TOMATO

Ultrastructural changes in tomato leaves of susceptible cv. Peto 95 an d resistant cv. Ontario 7710 infected with Pseudomonas syringae pv. to mato were followed by transmission electron microscopy. Up to 48 hours from the inoculation host cells of both cultivars looked quite normal and no bacteria were visible in the intercellular spaces; bacterial c ells were found only in the substomatal chambers. Afterwards, the leaf cells of cv. Peto 95 began to degenerate and bacteria invaded the int ercellular spaces which seemed enlarged. After 15 days the disorganiza tion was complete: tomato cells were plasmolyzed and the intercellular spaces were filled with bacteria. In the leaves of resistant cv. Onta rio 7710 no bacteria were observed later than 48 hours and no visible modifications occurred up to 15 days after the inoculation.