Acquired systemic resistance to tobacco mosaic virus in Nicotiana tabacum evoked by stem injection with Peronospora tabacina Adam

Resistance to tobacco mosaic virus (TMV) was induced in leaves of Nicotiana tabacum L. (cv. Xanthi and cv. Havana 423) by injecting spore suspensions of Peronospora tabacina Adam into the stems of plants. TMV lesions that developed on the leaves of stem-injected plants were 62% smaller and 32% fewer in number than their counterparts in control plants. While the difference in numbers of lesions on the leaves between injected and control plants decreased from the bottom to the top of the plant, the difference in the size of lesions was maintained at all leaf levels.