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Characterization of a Pepper Mild Mottle Tobamovirus Strain Capable of Overcoming the L3 Gene-Mediated Resistance, Distinct from the Resistance-Breaking Italian Isolate

April 1998 , Volume 11 , Number  4
Pages  327 - 331

Shinya Tsuda , 1 Masanobu Kirita , 1 and Yuichiro Watanabe 2

1Plant Biotechnology Institute, Ibaraki Agricultural Center, 3165-1 Ago, Iwama, Nishi-Ibaraki, Ibaraki 319-02, Japan; 2Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153, Japan

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Accepted 9 December 1997.

Green pepper plants with the L3 resistance gene usually develop necrotic lesions on leaves infected with a Japanese strain of pepper mild mottle tobamovirus (PMMoV-J). A recently discovered strain, PMMoV-Ij, has the ability to overcome L3 resistance. Phytopathological responses of a variety of plant species to PMMoV-J and PMMoV-Ij were determined and the coat protein (CP) sequence comparisons revealed both amino acids 43 and 50 of PMMoV-Ij were unique. This led us to believe that substitutions at these residues would enable PMMoV-J to overcome L3 resistance. This was confirmed by Western blot (immunoblot) detection of PMMoV-J containing both point mutations in upper uninoculated leaves of resistant plants. Computer models suggest the critical residues in overcoming resistance lie in CP regions that putatively interact with other subunits. These results contribute to our understanding of the virus's ability to circumvent plant resistance.

Additional keyword: elicitor.

©1998The American Phytopathological Society