The Systemic Infection by Tobacco Mosaic Virus of Tobacco Plants Coutaining the N Gene at Temperatures Below 28°C

Tobacco plants containing the N-gene are occasionally systemically infected with tobacco mosaic vims (TMV) at tempreratures below 28 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 systemicaily 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.