Elsevier

Virology

Volume 14, Issue 3, July 1961, Pages 340-358
Virology

Systemic acquired resistance induced by localized virus infections in plants

https://doi.org/10.1016/0042-6822(61)90319-1Get rights and content

Abstract

Inoculation of half-leaves of Nicotiana tabacum var. Samsun NN, with tobacco mosaic (TMV) virus induced a high level of resistance to TMV in the opposite half-leaves. Challenge inoculation with TMV of the resistant half-leaves 7 days after the first inoculation resulted in limited lesion formation; the lesions were consistently only one-fifth to one-third as large (in diameter) as were lesions in susceptible half-leaves, and they usually were fewer in number. Similarly, inoculation of lower leaves on a plant induced resistance in upper leaves and vice versa. Resistance was first detected in 2–3 days, reached a maximum in about 7 days, and persisted for at least 20 days. The uninoculated resistant leaves or half-leaves proved to be free of virus. The highest level of resistance developed when plants were kept at 20°C before and after the challenge inoculation. Resistance could be detected in plants kept at 29° after challenge. Complete protection was not obtained by increasing the ratio of the area first inoculated to that challenged. Resistance was induced by mixed infections by TMV and potato virus X (PVX), but leaves highly resistant to TMV alone were only slightly resistant when challenged with TMV plus PVX. Resistance was induced by TMV infection in detached leaves, in excised shoots, and in plants kept in the dark 2 days before challenge inoculation. No resistance was induced by mechanical or chemical injury or by viruses that do not cause necrosis.

The resistance induced by TMV is not specific for TMV. Leaves with TMV-induced resistance were resistant not only to TMV but also to tobacco necrosis virus, to turnip mosaic virus, and to tobacco and tomato ringspot viruses. The resistance was not as effective against these viruses as against TMV, but each of these local-lesion viruses induced a resistance in Samsun NN tobacco indistinguishable from that induced by TMV.

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Supported in part by a Public Health Service grant, E-2540, from the National Institutes of Health.

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