Retention of Chlorophyll in Lesions Produced by Tobacco Ringspot Virus

On intact and detached cotyledons of Caserta squash development of lesions produced by the tobacco ringspot virus was observed macroscopically and microscopically. Chlorophyll was destroyed in all portions of infected cotyledons except at the periphery of lesions and at the basal cells of trichomes in the center of lesions. Lesions were smaller on detached, infected cotyledons. Chlorophyll was retained in intact plastids clumped in a reticulate pattern throughout lesions on detached leaves. Chloroplasts in lesions were still deeply pigmented 40 days after cotyledons had been detached, whereas all other areas of the cotyledons were devoid of chlorophyll 1 week after the cotyledons were detached. Bacteria were observed in chlorotic cells in developing lesions and may be involved in cell disruption in portions of lesions