Abstract
When the lower leaves of Nicotiana glutinosa or Samsun NN tobacco, local lesion hosts for tobacco mosaic virus (TMV), were inoculated with TMV and kept at 20 °C in continuous light, non-viral lesions began to appear on non-inoculated upper leaves about 8 days later. It is postulated that these non-viral lesions might be induced by substances that move through stem tissues from the inoculated leaves bearing local lesions.