Abstract
Leaves of tomato plants (Lycopersicon esculentum cv. Fukuju no.2) inoculated with TMV-L11A (attenuated) or TMV-L (virulent) were compared by electron microscopy during the course of virus infection. Estimates were also made of the numbers of virions, the chlorophyll (a+b) content and the chlorophyll (a/b) ratio. Five days after inoculation, no differences were found in chloroplast structure, chlorophyll content or chlorophyll (a/b) ratio between healthy and infected plants, although a large number of virions were observed in these plants with both strains. From 10 to 30 days post-inoculation, changes in chlorophyll content and chlorophyll (a/b) ratios became apparent, the amount being in the order healthy>L11A>L. Virion accumulation was also much greater in cells infected with L than that with L11A. In both cases, chloroplasts were swollen and finally often ruptured. Their lamellar systems, however, remained essentially undamaged. Even though the L11A never induced mosaic symptoms, this attenuated strain also caused some ultrastructural changes in chloroplasts.
