1Department of Plant Microbiology and Pathology, University of Missouri, Columbia, MO 65211, U.S.A.; 2Plant Protection Institute, Hungarian Academy of Sciences, P.O. Box 102, 1525 Budapest, Hungary; 3Department of Plant Pathology, University of Nebraska, Lincoln, NE 68583, U.S.A.; 4United States Department of Agriculture, Agricultural Research Service, Columbia, MO 65211, U.S.A.
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Accepted 30 April 2004.
A new variety of Nicotiana edwardsonii, designated N. edwardsonii cv. Columbia, expresses pathogenesis-related (PR) proteins in a temporal manner 45 to 49 days postplanting and also exhibits enhanced resistance to Tobacco mosaic virus, Tobacco necrosis virus, and Tomato bushy stunt virus. In contrast, PR proteins were not expressed in the original N. edwardsonii variety at comparable ages but were induced after onset of a hypersensitive response to viral infection. The temporal induction of PR proteins in ‘Columbia’ was correlated with increases in salicylic acid and glycosylated salicylic acid. Earlier studies noted that some Nicotiana hybrids derived from interspecific crosses constitutively express PR proteins, but the genetic basis of this phenomenon had not been investigated, likely because many interspecific Nicotiana crosses are sterile. However, the close genetic relationship between N. edwardsonii and ‘Columbia’ indicated that a hybrid between these two plants might be fertile, and this proved to be true. Genetic crosses between ‘Columbia’ and N. edwardsonii demonstrated that a single, dominant gene conditioned temporal expression of PR proteins and enhanced resistance. This gene was designated TPR1 (for temporal expression of PR proteins).
© 2004 The American Phytopathological Society