The systemic infection by tobacco mosaic virus of tobacco plants containing the N gene at temperatures below 28 C

Tobacco plants containing the N-gene are occasionally systemically infected with tobacco mosaic virus (TMV) at temperatures below 28 degrees C, but contain low concentrations of virus: they often fail to set seed, and can outlive healthy control plants. Infection is thus similar to that induced when N-gene tobacco plants are grafted onto systemically infected tobacco lacking the N-gene. Shoots from systemically infected N-gene plants can induce systemic infection in other graft-inoculated N-gene plants. Stem sections of N-gene tobacco plants act as good conduits for TMV between plants lacking the N-gene, and girdling experiments suggest that virus movement probably occurs in the phloem.