Systemic acquired resistance induced in hypersensitive plants by nonnecrotic localized viral infections.
Localized symptomless infections of cucumber cotyledons and first foliage leaves by tobacco mosaic virus (TMV) induced systemic acquired resistance in other leaves of the same plants inoculated 2 weeks later with tobacco necrosis virus. Diameters of lesions that developed after the second inoculation were 35% less and lesion numbers were 30% fewer than in control plants not previously inoculated with TMV. Thus, necrosis after the first inoculation was not prerequisite to virus-induced systemic acquired resistance.
Roberts
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Department of Plant Pathology, University of Florida, Gainesville, Florida 32611, USA.